The influence of water, silica fume and ground granular base slag was found to have a significant impact on the extent of low carbon concrete behaviour in terms of compressive strength and embodied carbon. While the concrete compressive strength for normal concrete increases with reducing water content, it is observed that the low carbon concrete using lightweight aggregate material increases in compressive strength with an increase in embodied carbon. From the result of the analysis, a function was developed that was able to predict the associated embodied carbon of a concrete mix for a given water-to-cement ratio. The use of an alkaline solution is observed to increase the compressive strength of low carbon concrete when used in combination with ground granular base slag and silica fume. It is further shown that ground granular base slag contributes significantly to an increase in the compressive strength of Low carbon concrete when compared with pulverised fly ash. The optimised mix design program resulted in a 26% reduction in embodied carbon and an R The Intergovernmental panel on climate change (IPCC) projected zero-carbon emissions by 2050 if a 2 °C drop in global temperature is to be maintained [Embodied carbon encompasses carbon dioxide associated with extracting, manufacturing, transporting, and installing building materials. With an average of 66 billion square feet of buildings in construction every year, there are about 3.8 billion metric tons of COintained . With anConcrete as the most frequently used material after water uses cement as its major raw material and has been noted to be responsible for a very high carbon footprint . Carbon It has been shown that the built environment contributes about 10% of the global annual emission while in 2020, it accounted for 37% of the global emission . The repThe application of ANN in the effective prediction and simulation of concrete behaviour is shown to be effective when there is a large repository of an effective dataset, which will ascertain the condition for which the validity of the prediction can only be ascertained and accepted. As the production of low carbon concrete is limited to the scarcity of dataset due to the variability of sustainable alternative concrete binders, the effectiveness of the ANN model for a small and limited dataset becomes a concern. A simplex algorithm as a linear program that uses the optimality of a decision to predict desired outcomes, which is engineered with the ability to optimise small-scale data for effective prediction and decision-making is used in this study.2e to 500 kgco2e for 1 m3 of concrete. Similarly [Due to the cost intensity of the experimental program and uncertainty in the desired outcome, the use of numerical solutions to simulate and forecast likely outcomes cuts down on cost and time. The sensitivity of reinforced concrete pipeline deflection to the different soil filled depths was optimised by  using a imilarly  studied imilarly  and was imilarly  for whicPredicting concrete behaviour using ANN has been conducted by ,11 on a 2) value [The overdosing of cement in concrete is mostly responsible for the high carbon that is experienced in concrete. Construction materials use concrete and steel reinforcement due to their age-long benefits with cement and aggregate being the main raw materials of concrete which is noted for a very high carbon (CO2) value . The pro2) value . A combi2) value . The redThe development of LCC using lightweight aggregate requires the production of concrete with raw materials of low carbon footprint with the potential for better performance in terms of structural integrity and sustainability. In addition, the use of lightweight aggregate offers the benefits of reductions in the self-weight of the structure which eventually reduces the dead load transfer to the foundation. This reduction in self-weight offers an advantage for a clear span beam construction compared to conventional concrete where a high self-weight poses a threat in addition to the external load the structure needs to resist . The abiKanavaris et al.  use lighThe article is organised into sections. Section A reviews the most recent literature on the method of optimisation, research trends and the result obtained. Section B focuses on low carbon concrete and embodied carbon concrete dependent variables. Section C discusses the process of formation of the algorithm for this review. Finally, section D analyzes the result and presents the extent of optimisation of embodied water in the concrete mix.The use of nanomaterials has received increasing interest in reducing concrete greenhouse gas emissions. During cement hydration, the structure of the concrete materials condensed in size by nanometres using the calcium–silicate–hydrate (C–S–H) gel. This is because the particle size of cement ranges between 7 and 200 nm while that of aggregate has a particle size from millimetres to centimetres. It is then obvious that concrete can be described as a nanomaterial.2 reduces concrete water absorption by 58% while 3% nano-SiO2 reduces water absorption by 36.84%. This reduction in water absorption resulted in an improvement in concrete mechanical properties by densifying the concrete matrix during the hydration reaction. Available nanomaterials include Carbon nanotubes (CNTs), nano-SiO2 (nS), nano-Al2O3 (NA), graphene oxide (GO), nano-TiO2 (NT), nano clay (NC), nano-ZnO2 (NZ), and nano-Fe2O3 (NF) [The particle sizing of these materials ranges from 1 to 100 nm. The effectiveness of concrete carbon sequestration is enhanced with effective carbon hydroxide absorption and the reduction in chloride ion migration along with its diffusion coefficient. Studies have shown that 2% of nano-SiO2O3 (NF) ,24.Regarding the effect of concrete on embodied carbon, Tabrizikahou and Nowotarski  demonstrSimilarly ,30 have As the building structure comprises mainly a floor slab and beam, the options of modelling the floor slab and beam using a thin shell concrete from finite elements were explored as a design concept in reducing embodied carbon. The self-weight of this structural member was reduced to 44% and embodied carbon in the members was reduced to 57% . Similar3 for 80% GGBS cement replacement which confirms that GGBS significantly reduced embodied carbon as an SCM binder material. Thilakarathna et al. [The effect of material selection on the carbon footprint of structures has also been extensively studied ,33,34,352 emissions when conventional materials were replaced with lower embodied carbon material, which makes the issue of materials replacement a major consideration in embodied carbon reduction. The benefits of the application of low carbon concrete in construction will include but are not limited to enhanced physical and mechanical properties, reduction in raw materials and efficient energy consumption [Recent studies by González and García Navarro  have shosumption ,38. The sumption . The prosumption . Concretsumption ,41,42. −1 K−1 [The solar reflectance effect is often reported in the magnitude of 0 to 1. The fibre material thermal conductivity of some selected fibre raw materials is shown in −1 K−1  which is3, an embodied carbon reduction of 35% was reported. Additionally, fillers and additives were utilised gradually in substitution for the cement. Similarly, a further reduction to more than 60% was recorded with the use of granulated blast-furnace slag (GGBS). The result from these studies underscores the fact that there is a structural response to each degree of optimisation in consideration of the water-to-binder ratio. While a decrease in water-to-cement for conventional concrete is reported to enhance the compressive strength, for an LCC using recycled aggregates it has been observed that a reasonable amount of water is required to attain a high compressive strength for a lightweight recycled aggregate concrete [Low carbon concrete is concrete produced with consideration for the carbon footprint of the constituent materials in terms of sustainability and structural performance. The readiness and availability of concrete constituent materials with enhanced ubiquity during sourcing while placing emphasis on its low carbon content makes it a sustainable low carbon concrete material. Investigation of the impact of the water–cement ratio in concrete on its mechanical properties was studied by Proske et al. . The conconcrete .The use of waste or residual materials that uses a small amount of energy for production has the potential to produce concrete with a low carbon footprint. Cement is often replaced with materials such as silica fume, fly ash as well as wood ash. The work of Tam et al.  did showIt was observed that the use of recycled aggregate is effective when used in combination with fly ash as supplementary cementitious material (SCM) but was not suitable when combined with GGBS . The reaSilica fume is obtained from the production of silicon. It exists as a fine powder used in a slurry form to produce high-performance concrete. During the condensation of silicon dioxide and ferrosilicon alloy, silica fume is a by-product having the nature of an ultrafine power. It has the advantage of low permeability which is suitable to increase the concrete structural performance . The comFrom the Concrete Industry Sustainability Performance Report 2018 on performance data , the cliThe binder constitutes the core of embodied carbon in concrete which can partly be replaced with secondary cementitious material. This means that the binder CEM1 can be partially replaced with GGBS, pulverised fly ash or limestone, etc., to produce a low carbon concrete in a proportion to attain good structural performance. Concrete carbon content is measured as the embodied carbon associated with the measured slump as a benchmark for rating the embodied carbon in concrete which varies from A to E. From With preference from design options using low recommended minimum cement content and the allowable cement types, the highest levels of clinker replacement will ultimately reduce carbon emission in concrete. It is possible to predict maturity and strength using a time-temperature relationship since concrete strength is a function of the time between casting, testing, and curing temperature.The boundaries to established low carbon concrete have been set by the Low Carbon Concrete Group of the Green Construction Board (LCCG)  of the i2e/m3 for cement to 95 kg Co2e/m3. This implies that an increase in GGBS replacement will further reduce the embodied carbon. Following the strength rating of LCC, the embodied carbon rating for the different classes was recommended as shown in 2e/m3 for concrete in foundations, which lies within grade B, a further optimisation is likely to have a grade A for the foundation while not falling short of the required mechanical performance.It is expected that a limit of consideration in terms of LCC grade from the concrete design process to the construction stage would limit the extent of embodied carbon emission from the built environment. Given the tolerable value of 95–190 kg Co3) decomposition to calcium oxide (CaO) from the combustion of fossil fuels and electricity consumption [When considering the choice of sustainable concrete, the effect of carbon content outweighs the influence of other parameters on concrete while not ignoring structural integrity. From sumption . The usesumption . Alkali sumption . The relsumption . From thsumption . MATLAB sumption . To produce low carbon concrete (LCC) from previous studies, mix compositions were made from CEMI and other SCM materials at different mix proportions. Consideration from the literature has always been given mainly to the replacement of CEMI with SCM materials without considering the impact of water content on the carbon value. However, the effect of water is being considered only in terms of its workability which is measured by the slump value. The results of previous studies have focused on the correlation between compressive strength and embodied carbon. However, from the literature it was observed that the mechanical properties in terms of compressive strength of the low carbon concrete produced were limited and scarce; hence the need to consider the possibility of assessing the effect of water in the mix composition of low carbon concrete. The current study has established that the water composition in a concrete mix significantly influences the embodied carbon of the concrete for lightweight aggregate concrete via a series of optimisation techniques. This is possible because water tends to increase the porosity of concrete thereby enhancing the development of carbonation depth because the lightweight aggregate is obtained from recycled aggregate with a low density and with a tendency for high water absorption ,32,33,34The correlation of concrete raw materials to compressive strength and embodied carbon from Thilakarathna et al.  is shown3 of cement to attain the value of the compressive strength and embodied carbon equivalent of a combination of GGBS, PFA and Silica fume at less than 200 kg/m3. This implies that the use of GGBS, PFA and Silica fume as SCM for low carbon concrete compressive strength optimisation significantly influences the determination of its mechanical behaviour.MATLAB uses syntax that is suited for both scientific and engineering programming in a matrix and vector form for input and outputs. The applicable code is easily editable, especially with multifunctional scripts that allows the user easy access and flexibility. With the aim of accommodating all feasible concrete raw materials, the range of variables was extended to 12 concrete batches for one iteration. Due to the scarce and limited dataset for sustainable concrete and as part of the novelty to use the developed algorithm on a limited size of dataset, the sensitivity of the input parameters was examined from literature reviews of previous studies.Analysis of the concrete from ,33,34,35Concrete mix composition with the same compressive strength is observed to differ in the associated embodied carbon emitted. This also benchmarked the range of values of compressive strength for which certain values of embodied carbon can be estimated. A study of the assessment of embodied carbon emission of alkali-activated concrete substituted fly ash with metakaolin was carried out on low embodied carbon concrete and compared with Portland cement concrete (PCC). Calcium hydroxide and silica fume were used for the different mixes as an activator (admixture). It was reported that Ordinary Portland Cement (OPC) contributed to about 80% of embodied carbon in concrete .CEMI cements are produced from ordinary Portland cements (OPC) with a maximum of 5% additional material. OPC materials are usually 0–5% gypsum and about 95–100% clinker. Cement has been identified as the component responsible for the high carbon value of concrete. This is mainly possible due to the materials required for its production which includes the catenation of limestone. A look at the embodied carbon value for concrete components in The problem formulation is achieved by having an idea of the desired embodied carbon and compressive strength from the measured experimental value while being bounded by the design constraints, which are limited by the contribution of the proportion of the concrete variables and the measured outputs in terms of compressive strength and its associated embodied carbon. The measured compressive strength equates to a function defined by a proportion of the concrete variables, and it is repeated as a constraint for other measured output and represented as a matrix. An operation is performed to determine the entering and leaving variables using the non-negativity conditions expressed in Linear programming (LP) involves optimisation that meets both a linear objective function and a linear constraint. The laboratory results of low carbon concrete from ,33,34,35The standard linear programming problem can be written as 1 x1 + d2 x2 · · · + dn xn = ∑dj xjMinimise/Maximise Y = dsubject to the constraints11 × 1 + b12 × 2 + · · ·+ b1nxn ≤ c1b21 × 1 + b22 × 2 +· · ·+ b2nxn ≤ c2b...……………………… 1 × 1 +bm2 × 2 +· · ·+ bmnxn ≤ cnbm(or Bx ≤ c) and1 ≥ 0, x2 ≥ 0, . . . , xn ≥0 (or x ≥ 0). x1 x1 + · · · + dn xn is the objective function, Bx ≤ c the constraint and x ≥ 0 is the non-negativity constant [Here, Y = dconstant .The embodied carbon associated with the various concrete mix proportions from some studies was collated and shown in Optimisation of their concrete mix design for a target minimum embodied carbon was conducted using a linear programming (LP) algorithm and implemented in a MATLAB environment. The program algorithm resulted in the creation of the script ‘m-file’ that is transformed into MATLAB code containing the functions as well as the scripts.The objective function is to minimise the embodied carbon in one instance and maximise the concrete compressive strength at the second instance on data as reported in this literature, subject to variables in the concrete mix as shown in subject toThe decision variable x is implemented as followsWhere OPC = Ordinary Portland Cement,FA = Fine aggregate,CA = Coarse aggregate, w = Water, CH.A = Chemical admixture, GGBS = Ground granular base slag, PFA = Pulverised fly ash, NAOH = Sodium hydroxide solid, MEK = Metakaolin, NaSi = Sodium silicate, SF = Silica fume, EC = Embodied carbon, Concrete compressive strength.For the minimisation of embodied carbon, the objective function z is implemented as follows:For the maximisation of compressive strength, the objective function z is implemented as followsThe decision variables were subject to the minimum value of the parameters. The concrete mix design result as obtained from the literature were reproduced in a spreadsheet. A total of 84 datasets were used, and the 12 concrete mix design batches for each set of optimisations.Secondary Cementitious Materials (SCM) are materials used to replace Portland cement in a concrete mix primarily to reduce embodied carbon. Among the many SCMs available, GGBS is mostly preferred mostly due to its low carbon value and its ability to attain higher strength with age. However, as a water absorbent material, its hydration depends mostly on the presence of an activator which is mostly achieved by increasing the temperature of curing to between 50 °C and 80 °C to shorten its curing time. Other SCM includes flyash, metakaolin and silica fume .Similarly, as the strength of concrete is enhanced also by its aggregate sizing, GGBS increases concrete strength also by closing the concrete pore and acting as a binder material. Closing the concrete pores is further made unrealistic by the much water absorbent nature of GGBS which requires that much more are added, thereby making the concrete porosity wider, impacting the embodied carbon negatively. The porosity of the concrete then allows for the formation of carbon (carbonation) in the concrete, which is made possible by the aggregate sizing, water-to-binder ratio (w/c) and the SCM used. It is observed that while a carbonation depth of 15 mm is likely to be formed at w/c of 0.6 in 15 years, for w/c of 0.45, the carbonation will last 100 years before it attains 15 m .Admixtures such as superplasticizers are, therefore, introduced into the concrete mix to decrease the widening of the concrete capillaries which helps in reducing the formation of carbon and eventually reducing the embodied carbon.While several studies have shown that embodied carbon increases with an increase in concrete strength for concrete using recycled aggregate , etc., i2e/m3 at a compressive strength of 34.5 MPa. This is equivalent to a water–cement ratio of 0.3.The mixed batch considered for the optimisation has a total of 12 trial concrete mixes with material composition for each trial mix as shown in The concrete mix materials assign the desired behaviour for a given concrete use. This is influenced by its chemical and physical properties which often attain a complex structure because of the formation of new compounds, which is made possible by the hydration reaction of the binder. As the concerns for more sustainable and eco-friendly concrete gains momentum, the choice of materials for low carbon concrete cannot be over-emphasised. A practical and realistic approach will be to minimise cost and time on trial mixes which often result in material wastage and manpower loss. It becomes necessary to use the available tools of the linear program as an effective predictive method to select suitable concrete material composition from existing low carbon concrete data set.2e/kgm3 to 77 kg-Co2e/kgm3 was recorded using a water reduction from 150 kg/m3 to 75 kg/m3 at a minimal concrete strength decrease from 11.90 MPa to 10.2 MPa for a cement content of 150 kg/m3. This minimal decrease may be likened to the use of lytag aggregate compared to others. There was a remarkable increase in embodied carbon to 119.49 kg-Co2e/kgm3 and an increase in concrete strength to 32.258 MPa when 300 kg/m3 of cement was used. From Similarly, 2 value of 0.94 between the measured and the optimized concrete compressive strength.A similar effect of cement and water on embodied carbon and concrete strength was observed, but it was noted that PFA does not significantly affect the embodied carbon in concrete without water as a control. A summary of the optimized embodied carbon is shown in The sustainability performance of Alkaline Activated Concrete (AAC) as demonstrated in 2 value of 0.94 in comparison with the measured dataset. The average value of compressive strength for 12 concrete mixes for each batch was taken. The wide deviation shown in batch 1 is evident from the value of 650 kg/m3 and 1400 kg/m3 assumed), respectively, for fine and coarse aggregate as the dataset was lacking in these values. The relationship between the measured and the optimised can be expressed by the functionThe performance of the proposed model is shown in Energy efficiency is a concern that can be addressed within the purview of design and sustainability with consideration for available resources to enhance the minimal or near-zero carbon footprint of concrete. The chemical composition of concrete raw materials indicates properties that are representatives of methods and conditions of combinations and optimisation. Among the many concretes raw materials, superplasticizers, supplementary cementitious materials, alkaline solutions, water-to-binder ratio and the methods of curing influence the behaviour of low carbon concrete. Superplasticizers are useful concrete materials that enhance the workability of concrete. This is because not all water in the concrete during mixing is involved in the hydration process. However, high doses of superplasticizers are known to retard the early ageing of concrete. In this section, the influence of water-to-cement on the optimised model in terms of compressive strength and embodied carbon will be considered. 2e/kgm3 can be achieved with a water content of 95 kg. it further shows that for an increase in compressive strength, there is an increase in the water content for LCC with a similar increase in the embodied carbon. The optimal water content of 95 kg stabilizes the point where embodied carbon can be reduced to enhance the structural integrity of the mix.Most of the water used in concrete does not take part in the hydration process due to the chemical composition of the raw materials and the sulphate content of the water. The water used for concrete is often described as free water due to the lack of undesirable inorganic or organic substances such as sulphates, etc. The formation of cement paste from the hydration process of concrete formation is dependent on the setting time because of the quality of the water which eventually determines the concrete strength development pattern. The weather condition effects on the concrete strength development in extremely cold weather where the use of heated water may be necessary, have been studied by Brocklesby and Davison . Water aThe same observation is shown in Concrete shrinkage increases with higher water content for normal concrete; however, for low carbon concrete where the concrete bleeding occurs because of secondary cementitious materials, it is likely to be more and the remaining water that is not consumed by the hydration process will contribute to drying shrinkage. The embodied carbon contained in a concrete mix is dependent on the water content in the mix. As shown from previous studies, concrete embodied carbon, and the physical properties of binders, as shown in 2, and Al2O3 for which the influence on the microstructural enhancement of concrete will result in an increase in the mechanical behaviour of low carbon concrete.The physical properties of binder in terms of its surface area and specific gravity define the proportion of fine and coarse particles in it which predict the early age behaviour of concrete. This can be explained by its influence on the formation of capillary porosity, diffusivity, microstructural behaviour, and the extent of water percolation in the concrete. This also controls the hydration reaction as well as the water demand in concrete. Studies have shown that a binder with a higher surface area is obtained from a finer particle size for which the mechanical properties are higher than that of the coarse particle of a smaller surface area . Thus, tFollowing the dependence of embodied carbon and concrete strength on the water-to-binder ratio, it was shown in Equation (A1). See In the above equation, the function 2 in the paste, followed by a decline in the compressive strength. When GGBS is used in combination with other binders, such as cement, there is a reduction in the fineness of the composite binder which aids the hydration process on the nanoscale. The increase in water demand for the lightweight aggregate concrete is responsible for the decline in compressive strength as it enhances the increase in the specific area of the binder which allows for porosity that eventually causes high embodied carbon and low compressive strength. However, this effect is mitigated when used in combination with silica fume with its high pozzolanic potential which tends to increase the hydration process and eventually lead to early age strength. It was also noted that for an increase in silica fume from 22.5 to 150 kg/m3, there was an increase in compressive strength from 30.292 MPa to 50.33 Mpa; however, embodied carbon increases to 249.04 kg-co2e/kgm3 from151.38 kg-co2e/kgm3.It is observed that there is an increase in the compressive strength from 32.25 MPa to 51.21 MPa when the GGBS to Cement ratio increases from 1.0 to 1.25. This can be explained by the effect of fine GGBS particles on the hydration index. Dai et al.  conclude3 and water of 200 kg/m3, an embodied carbon of 315 kg-Co2e/kgm3 was observed with a concrete of 36.737 MPa. Sodium hydroxide and silica fume impact on the embodied carbon was minimal; however, a concrete strength increase was noticed. Further, an increase in cement and a reduction in the metakaolin resulted in an increase in embodied carbon to 409.35 kg-Co2e/kgm3 at a concrete strength of 63.45 MPa. This was also in combination with 100 kg/m3 of silica fume. On increasing the silica fume to 300 kg/m3 at no cement added but 100 kg/m3 of Metakaolin, the concrete strength increases to 86.97 MPa at an embodied carbon of 267.16 kg-Co2e/kgm3.Concrete mix design using alkali-activated concrete (AAC) and Portland Cement Concrete (PCC), using a combination of metakaolin, Sodium hydroxide, silica fume and sodium silicate shows a better structural performance. When the cement was completely replaced with 100% of metakaolin at 500 kg/mConsideration of the impact of water on concrete is necessary for the evaluation of the extent of embodied carbon from the concrete mix. The hydration process aided by the penetration of water in the concrete causes the leaching of calcium hydroxide from the concrete due to its high solubility . The rat3, there is decreasing compressive strength with an increasing water cement-to-cement ratio; however, for lightweight aggregate concrete, depending on the water absorption of the aggregate, there may be a need to increase the water content. This makes it difficult to conclude whether increasing or decreasing the water–cement ratio increases the concrete compressive strength for a low carbon concrete. The correlation of the function in Equation (A1) which is derived based on the low compressive strength to high water–cement ratio, attests to this variability for low carbon concrete and predicts the influence of water on concrete embodied carbon.The impact of water content on the concrete mix depends on the nature of the component mix constituent. The lightweight aggregate has a high water-absorbing tendency due to the use of recycled or supplementary aggregate. It also portends to the high variability of water content in determining its compressive strength. For normal concrete with a density of about 2400 kg/m3 is required to attain the minimum embodied carbon of 182.92 kg-CO2e/m3 at a compressive strength of 39.73 Mpa; however, the water absorption for a low carbon concrete is highly determined by the chemical and physical properties of the SCM binder material. It is observed from the mix optimisation, that the combination of GGBS and silica fume result in a concrete mix that has reduced embodied carbon at optimal compressive strength. Similarly, it is also shown that the use of alkaline activated concrete (AAC) or the inclusion of an alkaline solution influences the production of alumina-silicate gel, which is responsible for the enhancement of the compressive strength of low carbon concrete. Regarding the influence of water in the concrete mix, optimal water in the concrete of 83 kg/mThere are some other constraints that determine the behaviour of concrete, that were not considered in the linear algorithm as presented in this study, which can affect the prediction of the behaviour of concrete for small datasets. Further studies should consider the ability of how concrete behaviour can positively respond to changes in humidity, ambient temperature, and weather condition to reduce cost and carbon emission while considering a small dataset and concrete binders, determined accordingly.The optimisation of low carbon concrete was proposed in this study using the simplex algorithm. A set of concrete raw materials were evaluated and used as input variables which significantly impact the compressive strength and embodied carbon as the outputs. A MATLAB script was developed to solve the algorithm and for each iteration, the inputs were varied at a target and desired output. Different mix proportions were tried, and the corresponding outputs were measured. Based on the results of this study, the following conclusions were obtained.The water-to-binder ratio is a significant parameter that determines the embodied carbon of low carbon concrete. The determination of the embodied carbon value of low carbon concrete at the trial mix batch will minimise the cement overdose of the concrete and reduce the assumed uncertainties inherent in over-design.The water absorption rate for LCC is higher than the normal weight concrete for optimal compressive strength to be attained at a low carbon value,Alkaline activated concrete (AAC) offers the potential for a complete replacement of cement for sustainable, eco-friendly, low carbon concrete with good mechanical performance.The use of an alkaline solution enhances the hydration process of GGBS which is evident with the increase in compressive strength when used in combinationThe combination of two alternative binders for LCC improves the particle size fineness and eventually improves the binder hydration process which is optimal at the nanoscale.The combination of GGBS and silica fume portends the chance of a complete replacement of cement as a concrete binderIt is observed that GGBS has a comparative advantage over fly ash in terms of carbon reduction in concrete.


As part of this project, detailed tests of the concrete mix and hardened concrete were carried out in terms of compressive, bending, fracture and frost resistance after 150 cycles of freezing and thawing, and the pore structure in hardened concrete was assessed according to PN-EN 480-11. The endurance tests were performed after 7, 28 and 90 days. On the basis of the obtained results, it was found that the highest compressive strengths above 70.2 MPa were obtained for concrete with CEM III, 64.5 MPa for concrete with CEM I. Additionally, for concrete with multi-component cement, smaller drops in compressive strength were obtained and a more favorable pore distribution in hardened concrete was obtained. Concrete intended for road surfaces can be made of both CEM I and CEM III cement, as they meet the requirements of the technical specifications for roads with heavy traffic of heavy vehicles.The aim of this work was to reduce the carbon footprint of cement concrete by using multi-component cement with a high content of blast furnace slag. The analysis consisted of comparing the properties of the concrete mix and the hardened concrete made of the CEM I 42.5 R-NA cement commonly used in Poland and the CEM III cement with a large amount of blast furnace slag. The tests used cement in a constant amount of 380 kg/m The construction of such infrastructure consumes a very large part of the expenditure of each country; therefore, it is extremely important to increase the durability of the roads built in order to reduce maintenance costs in the future and maximize the life cycle of the pavement. A reduction in maintenance costs and an extension of the life cycle of road pavements is possible thanks to the use of cement concrete pavements. In Poland, the most frequently used cement for infrastructure is Portland cement CEM I 42.5, but its production requires a lot of energy, as it contains over 90% of clinker. The activities of many researchers in the field of the properties of cement concrete mainly concerned the modification of the concrete composition through the use of various types of aggregate, the amount and type of chemical admixtures and mineral additives ,7,8,9. A clinker ,15,16,17 clinker ,24,25,26 clinker ,28,29,30 clinker , and the clinker ,34,35,36 clinker . The use clinker ,39,40. T clinker ,42,43,44 clinker .3 and water absorption 0.80% and natural sand with a fraction of 0/2 with a density of 2.64 g/cm3. Two types of chemical admixtures were used in the form of a high-performance/strong admixture reducing water SP of the 3rd generation, in accordance with the PN-EN 934-1 [3 and an aerator with a density of 1.01 g/cm3 and water in accordance with the requirements of PN-EN 1008 [The tests were carried out with the use of two types of cements according to PN-EN 197-1 , cement EN 934-1  and PN-EEN 934-1  standard-EN 1008 . The pro2, Al2O3, Fe2O3 and small amounts of other materials. The raw meal, paste or slurry are finely ground, thoroughly mixed and therefore homogeneous. Portland cement clinker is a hydraulic material, at least two-thirds of its mass is composed of calcium silicates (3CaO SiO2 and 2CaO SiO2) and the remainder of aluminum and iron containing clinker phases and other compounds. The mass ratio (CaO)/(SiO2) must not be less than 2.0 [2). The remainder contains aluminum oxide (Al2O3) along with a small amount of other compounds. The mass ratio (CaO + MgO)/(SiO2) should exceed 1.0 [CEM I 42.5 R-NA contains more than 90% of Portland clinker (K), which is produced by sintering a precisely defined mixture of raw materials  containing elements, usually expressed as oxides, CaO, SiOthan 2.0 . The conceed 1.0 .The tests of the concrete mix, including the determination of air content, density, the temperature of the mix and consistency, were carried out 5 and 60 min after the completion of mixing the components in order to check the rheological behavior of the concrete mix. The vebe consistency tests were carried out in accordance with EN 12350-2 , and the3. Granite aggregate with a fraction of 2/8, 8/16 and 16/22 mm and natural sand with a fraction of 0/2 mm of the grain size are shown in C35/45 class concrete with a w/c coefficient of 0.40 was designed with the use of a plasticizing admixture and an air-entraining admixture. All tested concretes were made with a constant amount of cement of 380 kg/mThe grading of the mineral mix along with the recommended grading curves resulting from the requirements of the technical specification are presented in The assumptions of the research project were to determine the properties of concrete mix and hardened concrete after 7, 28 and 90 days of curing in accordance with the guidelines for using two different cements intended for use in road concrete surfaces with high traffic. The list of the compositions of the tested concrete mixtures is presented in The forming and storage of samples during maturation were performed in accordance with the requirements of EN 12390-2 . Tests oThe main research element of this project was to verify the frost resistance after 150 cycles analyzed with the use of the standard method in accordance with PN-B-06250: 1988  and for The influence of the type of cement on the properties of the concrete mix was determined 5 and 60 min after mixing the components under standard conditions. The consistency was determined in accordance with PN-EN 12350-3, the air content in the concrete mix in accordance with PN-EN 12350-7 and the density of the mix in accordance with PN-EN 12350-6. The results obtained during this study are summarized in Analyzing the obtained results of the consistency determination after 5 and 60 min, it can be seen that the highest parameters were obtained for the C_III concrete mix based on the CEM III cement. The concrete mix for CEM III tested after 60 min maintained the assumed consistency and air content. For the C_I mix based on CEM I, the consistency ranged from 14 s to 10 s after 60 min, and the air content from 5.8% to 5.1% after 60 min. All results were within the parameters’ range required by the specification.The effect of the type of cement on the compressive strength was determined according to PN-EN 12390-3 after 7, 28 and 90 days of maturation. The production and storage of 36 samples during the maturation period was carried out in accordance with the requirements of EN 12390-2. The average results of the obtained tests are summarized in When analyzing the obtained results of the compressive strength test, it should be noted that the highest values were obtained for C_III concrete based on CEM III after 28 and 90 days of maturation. Concrete C_I obtained higher strength after 7 days because it is made of CEM I 42.5 R-NA cement, i.e., with early compressive strength. Regardless of the type of cement, all concretes reached the minimum of 49 MPa required by the specifications. Concrete based on CEM III cement reached 44.5, 60.3 and 70.2 MPa, respectively, after 7, 28 and 90 days of maturation. For CEM I cement, the obtained results were lower by 4.8% and 8.1% after 28 and 90 days compared to CEM III. Greater strength and greater increases in strength of concrete based on CEM III cement result from the greater amount of mineral addition in the form of blast furnace slag, which exhibits long-term binding properties. The increase in the compressive strength of the concrete with the formula C_III in the period between 28 and 90 days was 16.4%.The influence of the type of cement on the bending strength was determined according to PN-EN 12390-5 after 28 and 90 days of maturation. The production and storage of 12 samples during maturation was performed in accordance with the requirements of EN 12390-2. The average results of the obtained tests are summarized in The highest flexural strength results were obtained for concrete with CEM III after both 28 and 90 days of maturation. Regardless of the type of cement, all concretes reached the minimum of 5.5 MPa required by the specifications. Concrete based on CEM III cement reached 7.0 and 7.8 MPa, respectively, after 28 and 90 days of maturation. For CEM I cement, the obtained results were lower by 2.9% and 10.3% compared to CEM III. The increase in the strength of concrete with formula C_III in the period from 28 to 90 days was 11.4%.The determination of the impact of the type of cement on the tensile splitting strength of the test specimens was performed in accordance with PN-EN 12390-6 after 28 and 90 days of maturation. The production and storage of 12 samples during maturation was compliant with the requirements of EN 12390-2. The average results of the obtained tests are summarized in The highest tensile splitting strength of the test specimens was achieved for C_I concrete after both 28 and 90 days. Regardless of the type of cement, all concretes reached the minimum of 3.5 MPa required by the specifications.Concrete frost resistance was tested in accordance with PN-B-06250:1988 using the standard method, the procedure for F150 freezing and thawing cycles. From each of the tested mixtures, 12 cubes with the side length of 100 mm were formed. The produced specimens were then immersed in water for 28 days. Six samples of each blend were then weighed and subjected to 150 freeze–thaw cycles. The remaining six samples were left immersed in water as reference samples. After 150 freeze–thaw cycles, the samples were weighed and visually inspected. The compressive strength of all samples was determined as the last step in the test procedure. According to the frost resistance criteria, PN-B-06250: 1988, the weight variation cannot exceed 5%, and the loss of compressive strength cannot exceed 20% in reference to samples made of the same mixture that have not been subjected to cyclic freezing and thawing. Moreover, the samples after testing must not show any cracks. The test results are summarized in When analyzing the obtained results of strength tests in the form of frost resistance after 150 cycles, it should be noted that the smallest decrease in compressive strength after 150 cycles of freezing and thawing, amounting to 4.1%, was obtained for concrete C3_III. The tested pavement concretes based on CEM I and CEM III met the condition required in the technical specification because the decrease in compressive strength was less than 20% and the weight loss of the samples was less than 5%.The characteristics of air voids in hardened concrete were determined in accordance with EN 480-11: 2008. Test specimens with dimensions of 150 × 100 × 20 mm were cut from cubes with a side length of 150 mm formed in the laboratory. The void characteristics were measured by the microscopic method using a computer system for automatic image analysis, Nikon SMZ1270 Navitar. Two samples of each tested concrete were selected for testing the properties of air voids. The image of the hardened concrete structure is shown in To determine the spacing of air voids, a calculation model was adopted, which assumes the presence of air voids of a specific diameter. It is a transitional model between the real state and the Powers model. The results of the air voids distribution in the hardened concrete are presented in The obtained average values of the analyzed parameters, determined in accordance with the EN 480-11: 2008  standardL) and the lowest micro air-void content (A300) were demonstrated by the concrete marked C_III based on the CEM III cement.The total air content is similar to the results obtained in the concrete mix air content method, determined by the pressure method (from 5.1% to 5.8%). The total air content in the hardened concrete ranges from 4.71% to 5.77%. The highest value of the air gap coefficient (2 emissions by over 30%. By analyzing the individual properties of the concrete mix, it can be stated that the C_III concrete mix has better rheological properties after both 5 and 60 min from mixing the components. Analyzing the results of strength tests, it can be concluded that the concrete with CEM III has a compressive strength higher by 9% after 90 days of maturation. The use of CEM III cement for the construction of cement concrete road pavements is a beneficial alternative for the future, as it results in the reduction in the carbon footprint and lower CO2 emissions [When analyzing the obtained test results, it should be stated that the pavement concrete with the use of CEM III/A 42.5 HSR-NA cement meets very high requirements for a modern concrete pavement intended for heavy traffic on motorways. The aim of the research work was to check the properties of concrete for two different cements, CEM I 42.5 R-NA, commonly used and required in Poland, and CEM III/A 42.5 HSR-NA, which is a very interesting alternative, especially in terms of reducing the carbon footprint and environmental protection. The composition of CEM III cement contains over 45% of blast furnace slag which is a waste material, and thanks to this we can reduce the carbon footprint and COmissions , at the For both cements, the specification requirements were met, both in terms of strength tests and durability tests.The use of CEM III multi-component cement in concrete allowed to achieve 71 MPa of compressive strength after 90 days of maturation, i.e., 9% more than for CEM I.The use of CEM III cement improved frost resistance, as the decrease in compressive strength was 4.1%, and 10.5% for concrete with CEM I.Concrete with CEM III multi-component cement achieved a better pore structure in the form of A300—3.15% and L—0.07.Multi-component cement increases the filling of the cement paste structure, and thus increases the durability of cement concrete by reducing the loss of strength by up to 60%.Based on the tests carried out for the C35/45 class pavement concrete tested on two different cements, CEM I 42.5 R-NA and CEM III/A 42.5 HSR-NA, the following conclusions can be drawn:


The strength characteristics of steel fiber-desert sand concrete (SFDSC) can meet the demands of C40 concrete, and this research can provide a reference for engineers using desert sand in their designs.In this study, to reduce the consumption of natural sand and improve the utilization rate of desert sand in western China, while preparing 14 groups of samples, desert sand is used to replace natural sand by the ratio of 20%, 40%, and 60%, and steel fiber is mixed with volume fraction 0.5%, 1.0%, 1.5%, and 2.0%. The mechanical properties of the specimens, including compressive strength, splitting tensile strength, and axial compressive strength were tested. Besides, the microstructures of the samples were analyzed by SEM, XRD, and acoustic emission detection technologies to identify the damage process. The results show that the desert sand can refine the microstructure and fill the pores, and it has good comprehensive properties at a 40% substitution rate. The compression properties of specimens are not apparently improved, but the tensile strength and deformation properties are significantly improved. The steel fiber with 1.5 vol% content behaves better, and the 28d compressive strength of the optimized group reaches 58.7 MPa. As a result, the polynomial fitting degree of total AE hits and stress level receives a more incredible goodness (R With the increasing demand for building materials, river sand begins to show the phenomenon of running out or even depleting2, and the massive mining of river sand has also brought severe environmental problems such as undercutting riverbeds and loss of sand and gravel3. Furthermore, there is a large number of desert areas around the world, which are formed by weathering of parent rocks; the sand in these areas has a low fineness modulus and high water demand, making it challenging to apply desert sand to cement4. In addition to alleviating the scarcity of river sand, the efficient utilization of desert sand will provide a reference basis for desert management in local areas.In recent years, the problem of carbon emission has been gradually focused on, and low-carbon green building materials have become the focus of research in the industry8, which can improve the mechanical properties of concrete in a reasonable mix ratio9. Mixing mineral admixtures11 and fiber reinforcement14 with desert sand concrete (DSC) has also been found to improve performance, which provides a practical reference to overcoming the DSC’s shortcomings. On the other hand, the properties of desert sand are different from river sand; it contains small amounts of alkali metal oxides such as K2O and Na2O, and active elements such as Si, Al, and Ca, which will produce potential hydration products to enhance the concrete properties15. However, the chemical composition and fineness modulus of desert sands are different in different regions16, affecting the universal law of desert sand materials17. Meanwhile, acoustic emission techniques have started to use in the damage detection of concrete, but concrete damage monitoring of compounds with steel fibers and desert sands has been relatively underreported.The critical reason for limiting the application of desert sand resources is the low fineness modulus, high water requirement, and concrete bleeding problem. Most studies have concluded that desert sands are finer-grained and play a good role in filling and improving the density of the paste18. According to available research23, adding fibers can inhibit the development of microcracks and restrain the tensile strain after cracking; which is an effective way to improve the mechanical (strength and shrinkage) properties of concrete, but researchers25 also claim there was a decrease in compressive strength after incorporation of fibers. Meanwhile, fiber distribution influences the strength of concrete26, which is in turn impacted by the matrix rheological properties27. Thus, the matrix’s quality and the fibers’ properties  will impact concrete performance28. As fiber reinforcement has been effective at improving the load-bearing capacity of concrete, it could be a feasible way to enhance the performance of desert sand concrete by adding fiber as well as improving the utilization of desert sand in the local area.According to previous research, it can be known that concrete has poor tensile properties, and in order to increase its ductility, fibers are added to concrete for reinforcementRds) and steel fiber contents (Vsf). The concrete axial compression process is characterized by the acoustic emission (AE) technique to analyze the fitting of total AE hits to stress levels. As a final step, SEM and XRD were performed to provide analytical verification of the microstructure. This study aims to provide an experimental basis for using desert sand resources as construction materials, which will also serve as a valuable guide for better understanding the characteristics of fiber and desert sand synergy, improving the effective utilization of desert sand resources, and facilitating local use in desert areas.Therefore, considering the convenience of obtaining materials in Xinjiang and the urgent need for environmental management in sandy areas, Taklamakan desert sand is selected in this paper to prepare samples and test the mechanical properties of 14 groups with different desert sand replacement rates  and steel fiber content (Vsf) on the performance of desert sand concrete (DSC), fiber content by volume and concrete design strength of C40. With a detailed mix design shown in Table 32 and (CECS 13-2009)33.Based on the previous researchAccording to Table After being cured to the age of 28d, samples were removed from the curing room and cleaned of surface debris and water before being tested for mechanical properties. The test parameters include compressive strength, splitting tensile strength, axial compressive strength and stress–strain curves. All steps were performed conforming to the Chinese standards norms (GB/T 50081-2019). The compressive strength of the DSC was tested by the compressive machine WHY-3000) with a loading speed was 0.06 MPa/s. The axial compressive strength was tested by the compressive machine (306A-3000) with the method of displacement controlling, and the loading speed was 0.1 mm/min; the axial compression process using the acoustic emission acquisition instrument (SAEU2S) for the measurement and acquisition of its internal damage data. In all of test samples, the maximum and minimum values shall not exceed 15% of the average. Figure 000 with Rds and Vsf. Overall, the performance of Rds at 40% is better, and there are slight differences in the performance between samples at 20% and 60% replacement rates, but all their strength has exceeded JZ-0. The addition of steel fibers showed a more significant improvement in splitting tensile strength; this may benefit from the fibers’ bridging effect, which effectively limits the development of inside microcracks during the damage process. The fiber content, however, was not found to improve compressive strength significantly, and Xu et al. also drew similar conclusions in their study34. In the following sections, we will discuss the mechanical properties separately.Figure Rds and Vsf on the compressive strength of DSC. It can be found that the highest strength of all groups was JZ-5 at Vsf = 0.5%/Rds = 40%, and was an increase of 27.6% compared to the JZ-0 compressive strength that was increased from 46 to 58.7 MPa. At the same Vsf, the compressive strength showed a trend of increasing and then decreasing with increased of Rds. In the group at Vsf = 1.0%, only the JZ-2 reached the highest strength of 56.8 MPa, which was increased by 23.5% compared to JZ-0, and other groups reached their peak at Rds = 40%. The results showed that Rds = 40% could present better strength properties, which is consistent with the findings of Lv et al.35. As an extra fine aggregate with a low fineness modulus, desert sand can fill the internal pores of the concrete and improve its compactness. Although desert sand has a large surface area and high water demand, it might absorb part of the water and play a role in dispersing colloids, which may positively impact mechanical properties11. On the other hand, even though the desert sand from the weathered parent rock has a more stable crystalline nature, its composition contains a certain amount of CaO and reactive Al2O3, which still shows some volcanic ash reactivity in the hydration reaction, promoting the generation of the hydration product C–S–H gel and improving the compressive properties of the matrix36. However, the high replacement perhaps reduces concrete workability. To achieve the slump requirement, we may need to increase water content, which may cause water secretion or not be easy to vibrate densely, thereby reducing performance.Figure Vsf, the compressive strengths of JZ-5 to JZ-8 are 58.7 MPa, 55.6 MPa, 53.8 MPa and 52.9 MPa, respectively; for the same Rds, the compressive strength gradually decreases with Vsf, and the strength was increased by 23.8%, 17.3%, 13.5% and 11.6% respectively compared with 47.4 MPa of JZ-13. However, an anomalous set of data was also observed, where the JZ-2 group showed an increase in strength when the Vsf was increased to 1.0%, then decreased in line with the trend, and the rest of the groups showed a decrease in strength with the increase in fiber content. It can be concluded that at lower Vsf, it is favourable to the compressive strength, but after exceeding 1.0%, the interfacial transition zone (ITZ) with weak mechanical properties will be formed on the surface of the fiber-to-paste and fiber-to-aggregate. Under stress, these parts will crack rapidly and gradually connect to form damaged cracks, resulting in a certain degree of deterioration of compressive strength37.It can be seen from Fig. Vsf = 0.5%, the splitting strength was enhanced with the increase of Rds. For all groups of fiber content, when Rds = 20%, the strength was increased by 25.2%, 57.5%, 88.6% and 94.5% compared to JZ-0, respectively, and the overall strength improvement trend increased with Vsf. In terms of the highest strength set of curves (Vsf = 2.0%), as the Rds increased, the splitting strength of the specimens reached 8.19 MPa, 8.92 MPa, and 7.30 MPa successively, and all groups increased at other Vsf levels. The matrix still contributes to the tensile strength of concrete even though its tensile properties are weak. During the test, uniformly distributed tensile stresses are generated in the compressed centerline, and the bearing capacity increases as the strength of the matrix increases. Nevertheless, special data points were observed in which the Vsf increased from 0.5 to 1.5% when Rds = 60% and the error limits of the data were larger; the strengths of the three groups were relatively close to each other without an obvious pattern. This phenomenon is attributed to the ultrafine properties of desert sand. Based on previous studies38, it is considered that desert sand within a certain replacement rate can ensure stable development of the strength of concrete; when Rds is too high (> 50%), the mixture cannot form a uniform particle gradation, which may lead to instability in the strength of the samples.As shown in Fig. 19. For the tensile strength enhancement, after matrix cracking, the fibers can effectively bear the tensile stress and better inhibit the development of microcracks40. Some studies have pointed out that the distribution of fibers may be affected by the yield stress, and the concrete performance may decrease due to an inadequate orientation of fibers25. By contrast, the hooked fibers improve the contact resistance between the two parts, and this form of embedding is similar to the anchorage of a reinforcement bar and greatly enhances the integrity of the fibers and the concrete.Unlike the aforementioned compressive strength law, the enhancing effect of fibers on the splitting tensile strength is very significant, which can effectively act as “micro reinforcement” to disperse the stresses during the tensile cracking process as the steel fibers are distributed in a 3D disorderly manner within the matrix, thus increasing its contribution to the bearing capacityRds, the axial compressive strength also shows the trend of increasing first and then decreasing and better mechanical properties when Rds = 40%. The strength of each group reached 42.3–43.8 MPa without much fluctuation when Rds = 20%. When the replacement rate was increased to 40%, the trend of each group showed unconformity, and the strength of JZ-5 at Vsf = 0.5% was only 45.3 MPa, which was 3.4% higher than 43.8 MPa of JZ-1, while with an increase of 15.7% and 16.1% the strength of JZ-7 and JZ-8 were more obviously increased to 49.5 MPa and 49.1 MPa, respectively. When the Rds was increased to 60%, only the strength of the JZ-9 still increased to 47.4 MPa, which was 4.6% higher than that of JZ-5, while a decrease in strength was observed in other groups. The results show that the fibers and the matrix resist stress together during the concrete compression process, but the lower tensile bearing capacity of the concrete during the tension process leads to tiny cracks first; at the same time, the stress is transferred to the fibers, thus limiting the further development of the cracks. This can lead to lower matrix performance and affect the axial compressive strength at higher Rds. Due to the fine particle size and high specific surface area of desert sand, a higher admixture will result in weaker parts of the matrix, decreasing mechanical properties41, which is consistent with the compression strength law. On the other hand, among the different loading methods in the uniaxial compression test, the displacement control, makes the internal damage have enough time to develop. In addition, the "confinement effect" during the loading process constrains the sample along the direction of tensile stress.The trend of axial compressive strength is similar to that of cubes, but the effect of factors is different due to the change in sample size. Figure Vsf = 1.5%. However, this pattern may be related to the randomness of fiber distribution. Perpendicular distribution of fibers to the compression direction can effectively disperse the tensile stress and limit the further development of microcracks by their bridging action42. It can be seen from Fig. Rds = 40%/Vsf = 1.5%, followed by Rds = 60% and Rds = 20%. Among the three curves, the 40% replacement rate shows a gradual increase in strength with increasing Vsf, and the strength starts to invert after the Vsf exceeds 1.5%, which is related to the ITZ inside the matrix. The remaining two curves largely show a negative correlation trend, where the strength at Rds = 20% is lower, its strength development is influenced by the concrete, and the compressive strength bearing capacity contribution is mainly based on the cement matrix. At the same time, the fibers mainly play a crack-arresting role and have little contribution in enhancing the compressive bearing capacity43.The fiber has a negative effect on the axial compressive strength at the high volume dose, but unlike the cube compressive strength law, it shows an increase in the axial compressive strength at Vsf does not show an obvious effect on the peak stress at the same Rds, but it improves the concrete ductility and the falling section after the peak stress tends to be moderate. In Fig. Vsf = 0.5% has an abnormal curve in the descending section. After the curve reaches the peak stress, it drops briefly and then appears as a slight rebound; there is a significant fluctuation in the stress–strain curve; the strain drops steeply when ε reaches 10 × 10–3, and local damage occurs in a very short time with a large amount of skin peeling off the surface and rapid crack occur. This situation indicates the unstable performance of DSC under a high replacement rate, the desert sand cannot play a suitable filling effect after the change of particle gradation, and the matrix compactness has defects. The highest peak stress was found in all samples when Rds = 40%/Vsf = 1.5%, reaching 49.5 MPa; compared with other samples, the average value of peak strain of fiber-reinforcement DSC was 0.0033, which was greater than the peak strain of 0.0026 for Ordinary Portland cement concrete (OPC); the average value of ultimate strain was 0.0052, which was greater than the peak strain 0.0032  occurs between 500 and 2000 s, and AE hits in this stage will be jointly affected by various factors. The AE event record of crossing the threshold value is random, so individual samples will appear as regular anomalies, but it does not affect the general law.As shown in Fig. 45. In Fig. 2 above 0.96. It can be concluded that the total AE hits show a positive correlation with the stress level, and as the stress continues to increase, the internal damage intensifies, and more AE events are triggered at this time.According to the relationship between AE hits and stress, two types of functions were selected for fitting. Figure Rds. In the DSC, the main silica phase is still the quartz, and it can be seen that the prominent peak of the quartz reaches the highest at 2θ = 26.77. With the increase of Rds, a more obvious change in the peak of quartz is observed, but this change does not have much effect on the hydration products. The silica content of the desert sand is lower than that of the normal sand, so the decrease in the quartz phase mainly results from increased Rds. In addition to the silica phase, the prominent diffraction peaks were plagioclase zeolite, calcite and calcium hydroxide stone, and a certain amount of aragonite was also observed, indicating that the samples had undergone a slight carbonation reaction while being cured to the test age. The DSC may have similar problems in terms of durability as OPC, which needs further study to explain.Figure 46.Figure Rds) and steel fiber contents (Vsf) were investigated experimentally, and the process of concrete damage under pressure was monitored by the acoustic emission detection (AE) method. Combined with scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD), the microscopic morphology of concrete was observed, which led to the following conclusions:Rds, the overall mechanical properties of the concrete show a trend of first increasing and then decreasing, and the reasonable Rds can play a “micro-aggregate effect” to optimize the pore structure and improve the compactness of the matrix, realizing the best performance according to the test results Rds = 40%.With the increase of Vsf due to the crack resistance effect of the fibers. However, the cement matrix contributes most of the concrete’s compressive strength, while fibers have a minor impact on the compressive strength.Steel fibers have a significant effect on the splitting tensile strength of DSC, which is positively correlated with the After fiber incorporation, steel fiber desert sand concrete (SFDSC) exhibits a higher ductility than Ordinary Portland cement concrete (OPC), and the ultimate strain of concrete is increased, effectively increasing its bearing capacity. The falling section curve of fiber concrete slows down after the peak strain, and the strains at the damage time are all greater than those of OPC.Rds = 40%/Vsf = 1.5%), and the compressive strength, splitting tensile strength, and axial compressive strength is 53.8 MPa, 8.26 MPa and 49.5 MPa, respectively.The SFDSC can meet the strength requirement of C40 concrete with the highest 28d compressive strength of 58.7 MPa. The optimum mix ratio is the JZ-7 group  with different desert sand replacement rates (


Using waste rubber tires for concrete production will reduce the demand for natural aggregate and help to reduce environmental pollution. The main challenge of using waste rubber tires in concrete is the deterioration of mechanical properties, due to poor bonding between rubber and cement matrix. This research aims to evaluate the mechanical and thermal properties of rubberised concrete produced by using different proportions of rubber powder and silica fume. Ordinary Portland cement was partially replaced with silica fume by amounts of 5%, 10%, 15% and 20%, while sand was replaced by 10%, 20% and 30% with waste rubber powder. Tests were carried out in order to determine workability, density, compressive strength, splitting tensile strength, elastic modulus, thermal properties, water absorption and shrinkage of rubberised concrete. The compressive strength and splitting tensile strength of concrete produced using waste rubber powder were reduced by 10–52% and 9–57%, respectively. However, the reduction in modulus of elasticity was 2–36%, less severe than compressive and splitting tensile strengths. An optimum silica fume content of 15% was observed based on the results of mechanical properties. The average shrinkage of concrete containing 15% silica fume increased from −0.051% to −0.085% at 28 days, as the content of waste rubber powder increased from 10% to 30%. While the thermal conductivity of rubberised concrete was reduced by 9–35% compared to the control sample. Linear equations were found to correlate the density, splitting tensile strength, modulus of elasticity and thermal conductivity of concrete with silica fume and waste rubber powder. Rubberised concrete produced by incorporating waste rubber tire particles could promote sustainable development by reducing the demand for natural aggregates. Rubberised concrete demonstrates lower density, higher impact resistance and toughness, and better sound absorption and heat insulation than normal concrete. The properties of rubberised concrete are affected by the parameters of rubber particles, namely rubber content, rubber particle size, and surface conditions of rubber particles. The mechanical properties of rubberised concrete are negatively affected as the content of rubber particles increases ,2,3, att3 [Previous studies have demonstrated that the mechanical strength of rubberised concrete reduced as the size of rubber particles increased. The size of rubber particles can be classified into (i) chipped tire rubber particles size ranging between 13 and 76 mm is used as coarse aggregate, (ii) crumb tire rubber particles with sizes ranging between 0.075 and 4.75 mm to replace fine aggregate, and (iii) ground rubber particles size ranging between 0.15 and 19 mm. Some studies reported using rubber powder in concrete where the size of the rubber is less than 1 mm [3 , polymer3 , high st3 ,12,13 an3 . Other t3 .Eldin and Senouci  reported2 [2. Pre-coated rubber crumbs with OPC paste slightly improved the strength of rubberised concrete, whilst the ether solution reduced the strength of rubberised concrete [It is essential to note that tire rubber demonstrates both hydrophobic and non-polar characteristics, leading to poor bonding between the waste rubber and Ordinary Portland cement (OPC) in the concrete and reduced strength. Hence, the surface modification of waste rubber to enhance the rubber OPC bond is essential . In orde2 ,26,27 haconcrete . The rubconcrete .4 solution and then sulphonated with NaHSO3 achieved a 41.1% increase in the adhesion strength of the rubber and OPC paste [Various surface treatment techniques have been investigated to improve the bonding between rubber powder and OPC matrix. Segre and Joekes  reportedPC paste . The trePC paste  and ultrPC paste ,39 improExtensive research reported that replacing OPC with silica fume increases the packing density and densifies the interfacial transition zone between rubber particles (crumbs and chips), aggregates, and OPC matrix, leading to better bonding and, thus, enhancing the strengths of rubberised concrete ,41,42. TIt is essential to conduct an experimental study to quantify the effects of different silica fume contents for rubberised concrete produced using different proportions of waste rubber powder. A comprehensive experimental study was carried out to analyse the thermal and mechanical properties of concrete containing different proportions of waste rubber powder and silica fume. The silica fume contents investigated were up to 20% at an increment of 5%. Three waste rubber powder contents considered were 10%, 20% and 30%. Waste rubber powder consisting of mesh 40 and mesh 80 was used in this research. The tests performed on rubberised concrete were workability, density, water absorption, compressive and splitting tensile strength, modulus of elasticity, shrinkage, and thermal properties.To overcome the challenges of depleting natural aggregate resources and environmental issues related to waste disposal, reprocessing automotive scrap tires into aggregates for concrete production is a feasible means to promote sustainable development. It is essential to note that the waste rubber tire contains natural rubber, polybutadiene rubber, and styrene butadiene rubber, which are hydrophobic and non-polar. This leads to poor bonding between waste rubber aggregates and OPC in the concrete thus affecting the mechanical strengths. Various surface treatment methods such as silane coupling agent  and NaOH3 was used in this research. A local seller in Malaysia delivered the silica fume. The specific surface area and specific gravity of silica fume were 3176 cm2/g and 2.32, respectively. The particle size distribution of silica fume was analysed using the Mastersizer laser diffraction equipment. The particle size distribution results of silica fume are presented in Type I, OPC with a specific gravity of 3.14 g/cmTo investigate the effects of waste rubber powder and silica fume content in the rubberised concrete, 13 concrete mixtures were prepared by incorporating different proportions of waste rubber powder and silica fume. Silica fume was used as an OPC replacement for up to 20% by the weight of cement at an increment of 5%. Waste rubber powder was used as a sand replacement, and the range investigated was from 0 to 30% . Waste rubber powder was prepared by combining mesh 40 and mesh 80 sizes at a volume ratio of 1:1. The British standard  was adopThe waste rubber powder was washed thoroughly using tap water for 10 min in a container to remove dust and organic materials. The waste rubber powder was kept at room temperature for 24 h until the surface dried state was attained. The mixing process was started by mixing dry ingredients in the concrete mixer until a homogenous blend was achieved. After that, water was added gradually, and the mixing was stopped once good consistency was observed. The workability of rubberised concrete was measured immediately using the slump cone according to ASTM C143 . Three sCylinders with 100 mm diameter and 200 mm height were prepared to measure rubberised concrete density and water absorption according to ASTM C642 . The watConcrete cubes of 100 mm were prepared to determine the compressive strength at 7 and 28 days, according to ASTM C39 . The splThe concrete prisms with dimensions of 40 mm × 40 mm × 160 mm were prepared to monitor the shrinkage at 7 and 28 days using a vertical digital comparator according to ASTM C157 . The iniThis section presents the experimental observations and discussions of the workability, density, water absorption, mechanical properties, shrinkage, and thermal properties of concrete comprising various proportions of waste rubber powder and silica fume.3, and the replacement of sand with waste rubber powder reduced the density of concrete. As the waste rubber powder content increased in the concrete mix, the average density of concrete decreased in the range of 6% to 11%, depending on the rubber powder content. The lowest density of about 2100 kg/m3 was recorded by rubberised concrete with 30% rubber content. This reduction could be attributed to the lower specific gravity of waste rubber powder compared to the sand. Similarly, Wang et al. [As presented in g et al.  also foug et al. , where tThe average water absorption of concrete with waste rubber powder was higher than the control specimens. The highest water absorption of 5.48% was observed in the 5SF-30R. The hydrophobic characteristic of waste rubber powder caused air to be trapped at the interfacial transition zone in concrete, leading to higher water absorption. Furthermore, workability reduced as the rubber content increased, which eventually led to the development of air voids. The replacement of OPC with silica fume reduced water absorption in concrete. For instance, the average water absorption of concrete (5SF-10R and 20SF-10R) decreased from 2.4% to 1.68% at 7 days, and 2.68% to 1.95% at 28 days as the content of silica fume increased from 5% to 20%. This was due to the pozzolanic reaction of silica fume, which reduced voids and pores by the supplementary hydration. As a result of the increased calcium silicate (CSH) gel generation, the concrete surface becomes more compact and has less porosity .The average compressive strength of concrete containing silica fume and waste rubber powder at 7 and 28 days is presented in 3 [Furthermore, the hydrophobic characteristic of rubber particles caused weak bonding at the interfacial transition zone and reduced compressive strength. The decrease in the workability due to the increase in rubber content, as reported in 3 .Overall, it could be observed that the compressive strength increased as the silica fume content increased for concrete with the same rubber content. The average compressive strength of concrete with 10% rubber powder increased by 10.6% and 16.6% when the silica fume content increased from 5% to 10% and 15%. Silica fume enhances the bonding between waste rubber powder and OPC by enhancing the interfacial transition zone, and leading to an increase in compressive strength ,48,70. GThe average modulus of elasticity for concrete containing waste rubber powder and silica fume is illustrated in This experimental study measured the average shrinkage of concrete with silica fume and waste rubber powder at 7 and 28 days, as presented in It could be observed that shrinkage increased as the content of silica fume increased. The average shrinkage at 28 days for concrete containing 10% waste rubber powder increased from −0.044% to −0.056%, as the silica fume content increased from 5% to 20%. It was reported that silica fume has a negative impact on the shrinkage of concrete as the refinement of pore size distribution led to a further rise in capillary tension and more contraction of the OPC paste . It was The thermal conductivity and specific heat of all concrete samples are presented in The average specific heat capacity of concrete containing silica fume and waste rubber powder was higher than the control sample. This could be attributed to the higher specific heat capacity of silica fume (750 J/kgK ) and wasScanning Electron Microscopy (SEM) was used to investigate the effects of silica fume on the microstructure of rubberised concrete. The microstructural images of concrete containing various proportions of silica fume are presented in p-value, in order to evaluate whether the effects of silica fume and waste rubber powder content were statistically significant or not significant. An alpha (α) level (error probability) of 0.005 was chosen for the ANOVA test. Furthermore, the p-value or probability value represents the probability for a specified statistical model that, when the null hypothesis is true, the statistical summary would be equal to or more extreme than the actual observed outcomes. While F-value is the ratio of change in sample means to change within samples. The larger the F-value, the more the difference between sample means relative to the difference within the samples. According to the previous study [p-value must be lower than 0.05. p-value less than 0.005 and an F-value greater than F-critical, which indicated that varying the proportions of silica fume up to 20% could affect the properties of concrete with rubber content up to 30%. In addition, as the waste rubber powder content increased in analysis, the p-value decreased significantly, and F-value increased. This shows that waste rubber powder content has significantly affected the density, compressive strength, splitting tensile strength, elastic modulus and thermal conductivity of concrete.The analysis of variance (ANOVA) is a statistical method for separating observed variance data into distinct components, so that additional tests may be performed. In this research, the ANOVA technique was used to evaluate the statistically significant parameters on the density, compressive strength, splitting tensile strength, elastic modulus and thermal conductivity of concrete containing the various percentages of silica fume and waste rubber powder. The ANOVA method was used to obtain F-value and us study , the modThe linear correlation technique was utilised to show the relationships between two quantitative variables. The linear model is one of the most widely used models in regression analysis because of its simplicity, practicality, and accuracy ,83. Prev2) value obtained from the regression analysis shows the relevance between the regression curve and data points; the R2 value that was greater than or equal to 0.7 indicates a strong correlation between the test results [2 values for various linear relationships range from 0.7 to 0.89. It shows that all linear relationships have a strong positive correlation between variables. A linear relationship was developed between the compressive strength and the density, as displayed in 2 and adjusted R2 were 0.7 and 0.69, respectively, which confirmed the relationship’s applicability [2 value equals 0.62. In addition, Rashid et al. [2 value equals to 0.86. The developed equation is provided below:The coefficient of determinant (R results . Further results . From Ficability . A previcability  developed et al.  found a cu = Compressive strength in MPafρ = density in kg/m32 value between compressive strength and splitting tensile strength for concrete are reported [reported ,89. The ct = Splitting tensile strength in MPafcu = Compressive strength in MPafE = modulus of elasticity in GPacu = Compressive strength in MPaf2 value of 0.68. While Unal et al. [2 value of 0.82. The linear equation obtained from the current study is presented below:l et al.  developeρ = density in kg/m32 value of 0.85. The linear equation found from this research is described below:cu = Compressive strength in MPafThe compressive strength, splitting tensile strength and elastic modulus of rubberised concrete was improved using silica fume. The silica fume content has significant effects on the compressive strength and modulus of elasticity where the increment was about 15% when the silica fume content increased from 5% to 15% at a rubber content of 30%. The increment in the splitting tensile strength was less than 10% in this case. The optimum silica fume content of 15% was determined from this study as the mechanical properties of rubberised reduced as the silica fume content of 20% was adopted. Nagarajan and Shanmugasundaram  also repDifferent optimum silica fume content was reported in the previous studies. Gupta et al.  investigThe workability, mechanical properties and thermal conductivity of concrete decreased as the waste rubber powder content increased. Increasing rubber powder content led to higher water absorption and shrinkage. The partial replacement of OPC with silica fume by up to 15% improved the mechanical properties of rubberised concrete. Further increases in the silica fume content caused a reduction in mechanical properties. The ANOVA analyses confirmed that the silica fume and rubber powder content have significant effects on the properties of rubberised concrete.The mixture with a combination of 15% silica fume and 10% waste rubber powder was determined as the optimum proportion based on the mechanical performance. The reduction in compressive strength, splitting tensile strength and elastic modulus was less than 10%, and it achieved a compressive strength of more than 25 MPa. The thermal conductivity was 11% lower than the control sample.A minimum of 20% rubber powder was required as a sand replacement in order to achieve a thermal conductivity below 1.5 W/mK, which represented a 20% reduction in thermal conductivity compared to the control sample. With 30% rubber powder, a thermal conductivity as low as 1.2 W/mK could be achieved, but the compressive strength was less than 20 MPa.The proposed linear regression models could predict the relationships between splitting tensile strength, modulus of elasticity and thermal conductivity with compressive strength at an acceptable accuracy.In this experimental investigation, rubberised concrete was developed by incorporating silica fume and rubber powder as partial replacements for OPC and sand, respectively. The rubber powder with Mesh sizes of 40 and 80 were used at a volume ratio of 1:1 to achieve better packing density. The workability, water absorption, shrinkage, and thermal and mechanical properties of rubberised concrete were investigated by varying the proportion of silica fume and rubber powder. Based on the experimental outcomes, the following conclusions could be drawn:Even though this research presents comprehensive results on the mechanical and thermal properties of concrete with waste rubber powder and silica fume, further research on the long-term durability, flexural strength and impact resistance of concrete with waste rubber powder and silica fume should be conducted in order to provide a better understanding on these properties. In addition, the effects of combining silica fume with different surface treatment methods, such as NaOH and ethanol for waste rubber powder can be explored.


Prescription refills are long-term prescriptions for chronic patients in stable status, which varies from country to country. A well-established prescription refill system is beneficial for chronic patients’ medication management and facilitates the efficacy of clinical care. Therefore, we carried out a bibliometric analysis to examine the development of this field.Publications on prescription refills from 1970 to 2021 were collected in the Web of Science Core Collection (WoSCC). Search strategy TS = “prescri* refill*” OR “medi* refill*” OR “repeat prescri*” OR “repeat dispens*” OR TI = refill* was used for search. VOSviewer was applied to visualize the bibliometric analysis. A total of 319 publications were found in WoSCC. Study attention on prescription refills has shown a steady rise but is still low in recent years. The United States was the most productive country, which had the highest total citations, average citations per publication, and the highest H-index, and participated in international collaboration most frequently. The University of California system was the most productive institution. The U.S. Department of Veterans Affairs was the institution with the most citations, most average citation, and highest H-index. Sundell was the most productive author, and Steiner J. F. was the most influential author. “Adherence,” “medication,” and “therapy” were the most prominent keywords.Publications on prescription refills have increased rapidly and continue to grow. The United States had the leading position in the area. It is recommended to pay closer attention to the latest hotspots, such as “Opioids,” “Surgery,” “Differentiated care,” and “HIV.” A prescription refill is a long-term prescription for chronic patients in stable status. In the United States and Europe, prescription refill policy has been a general tool in the national health insurance system with specific laws and policies . PrescriHowever prescription refills in some developing countries were still in the exploration phase, and the system of prescription refills has not been established yet, for example, in China. Since 2015, some regions in China have begun to provide the prescription refill service, but different regions have different regulations on expiration dates, types of disease, and drugs in the prescription refill system . HoweverBibliometrics, proposed by Prichard, is employed to review the literature and predict the development of scientific research, by applying literature systems and literature metrology characteristics as research objects, and using statistical methods to study quantity relationships and laws between literature and literature systems . It can Based on a bibliometric analysis conducted on the Web of Science Core Collection (WoSCC), the study analyzed various literature on prescription refills published between 1970 and 2021 using the VOSviewer from the perspective of co-occurrence and clustering. We aimed at providing the research status, trend, and forefront in the study of prescription refills to provide the reference for the researchers’ follow-up research.We performed a bibliometric analysis in WoSCC, a database strictly evaluating publications and updating them adequately to provide the most influential and reliable information , 9.The retrieval strategy was as follows: TS = “prescri* refill*” OR “medi* refill*” OR “repeat prescri*” OR “repeat dispens*” OR TI = refill*.The screening flowchart is shown in The articles were retrieved and screened by two researchers, and the criteria for screening and inclusion were: (1) language was “English,” (2) publication type was “article,” (3) data source was WoSCC , (4) published from 1 January 1970 to 31 December 2021, (5) the topic was prescription refills. Additionally, references of all included studies were searched.To make sure the topic of the included literature was prescription refills, two researchers, based on back-to-back methods, read abstracts of the retrieved articles and excluded 520 manuscripts that were unrelated to medicine, such as materials science (101), engineering (101), metallurgy (52), chemistry (46), physics (41), environmental sciences (30), and plant sciences (27). The two researchers read the full text of articles in the field of medicine and excluded about 230 articles whose objects or aim of research were not prescription refills.In the end, 319 manuscripts were included, and the detailed information of the manuscripts included was presented in 2 , among which the number of publications, average citations per publication, and the H-index were obtained from the Citation Report in the Web of Science. Bradford’s law was used to identify and analyze core journals. In Bradford’s law, if journals were ranked in decreasing order of a number of publications in a specific discipline, then journals were classified into “core journals,” “related journals,” and “non-related journals” groups, respectively, with the same amount of publications and each group has the number of journals as 1:n:n2 .Microsoft Excel 2016 were used to analyze and draw the number of publications, the average number of citations per publication, and the H-index. Meanwhile, Microsoft PowerPoint 2016 was applied to draw the flowchart of literature screening. Literature was imported to the VOSviewer  to draw co-occurrence maps of countries, authors, and keywords.f(x) = a/[1 + b × exp(–c × x)] (f(x) = a/[1 + b × exp(–c × x)] was used to fit the cumulative number of publications, with the point of maximum growth being the inflection point of the curve T = ln(b/c) (x representing a specific year and f(x) representing the cumulative number of publications for this year.The statistical package SPSS  was used to analyze the trend of publications using a logistic growth model –c × x)] , which h–c × x)] . The tim ln(b/c) , and x rf(x) = 934.268/[1 + 554.375exp (−0.107x)] (R2 = 0.981)}. It can be predicted from the model that the growth rate of publications might be the highest in 2028 [T = ln(b/c) = ln55(4.375/0.107) = 59.04] and gradually decline after 2028 with a continual increase in the cumulative number of publications.This study included 319 publications published from 1970 to 2021 in WoSCC. Trends in the number of publications are shown in By 31 December 2021, the publications included had been cited 7,349 times, with an average of 23.41. The annual citation number of the publications has stayed at a high level (more than 300 times) for a decade and continued to rise . The H-iA total of 47 countries or regions published articles related to prescription refills. The United States was the most productive country with 172 publications, followed by the United Kingdom (41 publications), Sweden (20 publications), Canada (18 publications), the Netherlands (16 publications), Australia (14 publications), South Africa (10 publications), China (9 publications), Ireland (6 publications), and Switzerland (6 publications) . The UniThe University of California system was the most productive institution with 20 publications, followed by the U.S. Department of Veterans Affairs (19 publications), Harvard University (13 publications), and others . The U.SThe top three productive authors are shown in The 319 articles were published in 148 journals. Based on Bradford’s law, nine journals were defined as “core journals” in the area . The mosThe assessment of refill compliance using pharmacy records: methods, validity, and applications; measurement of adherence in pharmacy administrative databases: a proposal for standard definitions and preferred measures; factors associated with medication refill adherence in cardiovascular-related diseases: a focus on health literacy; adherence in glaucoma: objective measurements of once-daily and adjunctive medication use; medications scale (ARMS) among low-literacy patients with chronic disease.The top five cited articles are shown in Keywords can be analyzed to find research hotspots and core content. Keywords such as “medication” were combined or unified to obtain a better perspective. For example, “medication adherence,” “persistence,” “compliance,” and “patient adherence” were unified as “adherence.” VOSviewer was used to visualize the frequency of keywords. A total of 78 keywords whose frequency was at least five times were analyzed.“Adherence,” “medication,” and “therapy” were the most prominent keywords , indicatBased on the bibliometrics and the visualization software, we aimed to explore the research trends and hotspots in the field of prescription refills from 1970 to 2021. The total number of publications from 1970 to 1994 was 25, and the average annual number of publications was 1, indicating very low attention on prescription refills in the 25 years. As this period was the beginning of literature research, growth of the literature was slow. From 1995 to 2009, the total number of publications was 59, and the average annual number of publications was 3.9 with a slow upward trend. After 2010, publications began to significantly increase and exceeded 20 publications in 2016. It can be seen that study attention on prescription refills has shown a steady rise. The number of publications showed a growth trend, and 2028 might be the year with the highest publication growth rate. This research field may remain a hotspot in the next few years. According to the analysis of the H-index, we found that the highest H-index was 14 in 2010, and the number of publications in that year was 17, indicating that the publications of this year were of great value to the field of prescription refills and deserved more attention. The highest number of citations in 2021 demonstrated an increasing emphasis on prescription refills. The H-index had decreased as the data in the last 5 years were close to the data collection time (31 December 2021). However, the publications in recent years would have more citations.The publications not only presented a dynamic time trend varying with the years but also showed varieties among different countries. The United States, the United Kingdom, and Sweden ranked as the top three productive countries, accounting for 73.04% of the total publications. The United States showed its dominant position in this research field with excellent performance in publication outputs, H-index, total citations, and average citations per publication. As a country with most international cooperation, the United States has cooperation projects with African countries, especially in HIV research. It conducted a study with Botswana on the impact of pharmacy supplement data on the outcome of virology treatment for HIV-infected adolescents in Botswana . The UniThe prescription refill system is closely related to the development of hospital pharmacy. Clinical pharmacy originated in the United States in the 1960s and was introduced in the United Kingdom in the early 1970s , which wEurope, the United States, and other countries have established a mature prescription refill system, which has become a basic tool of the national health insurance system, with specific laws and regulations to improve the implementation of policies. In the United States, prescription refills were prescribed by doctors for patients with chronic diseases in stable status and in need of long-term drug treatment. Pharmacists reviewed prescription refills, recorded, and followed up on patients’ medication. Hospitals and pharmacies throughout the country have prescribed categories of drugs for long-term use. Prescription refills were valid for 12 months. In addition, the details of refill management were mandated in Section 22 of Part 1306 of the Code of Federal Regulations  or physiological drug effects  primary healthcare systems on prescription refills, (2) studies on the compliance of patients with chronic disease, (3) patients with hypertention with asthma, (4) prescription refills of patients with AIDS, (5) prescription refills of patients with hypertension; (6) prescription refills of patients with diabetes. These six clusters will be the main focus of prescription refills in the future. Asthma, AIDS, hypertension, and diabetes were the top four types of diseases in prescription refill research. Studies have shown that interventions such as pharmacist-led interventions, regular follow-up, text message alerts, and scheduled drug programs at community pharmacies contributed to increased drug supplementation rates for these four diseases –39. In aThe research methods included in the study can be roughly divided into three categories: first, the analysis of patients’ adherence to the advantage side through the pharmacy record database , 41; secAt the same time, we analyzed the frontiers and hotspots of prescription refills. Results showed that the keywords “Opioids,” “Surgery,” “Differentiated care,” “HIV,” and “Barriers,” “Africa” have emerged in the last 5 years. It can be seen that the differentiated care of AIDS and the application of postoperative opioids have become a hotspot in the field of prescription refills. The study by Solouki et al. discussed the application of opioids in postoperative analgesia . The stuCompared with the traditional method of reading numerous studies and summarizing it to obtain the research status of prescription refills, our bibliometric analysis can provide researchers with an intuitive and quick way to obtain information in this field. Researchers can obtain the required information purposefully according to the contents displayed in the article, which improves the efficiency of the scientific research.Our research also had some limitations. First, these publications were only derived from the SCI-E and SSCI of the WoSCC database, which might cause relatively scarce retrievals, although the WoSCC database strictly evaluates the literature and is most frequently used for literature metrology analysis . Second,Recently, the number of publications on prescription refills has been increasing rapidly and continues to grow. The United States has the leading position in the area. It is recommended to pay closer attention to the latest hotspots, such as “Opioids,” “Surgery,” “Differentiated care,” and “HIV.” These results provide researchers with a visual and quick way to get information about prescription refills.YW and ZZ put forward the idea. RF and YL designed the study. HX and RF collected the literature and wrote the manuscript. YW and HZ revised the manuscript. XS and ZZ prepared the figures and tables. YW and HZ supervised and administrate the project. YW acquired the funding. All authors contributed to data analysis, drafting, and critically revised the study, agreed to be accountable for all aspects of the work, read, and approved the final manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.