In the construction industry, concrete is the most utilized building material. It is produced from different natural resources such as sand and gravel, as well as cement. The production of concrete is causing harm to the environment, yet its use became a necessity. To solve this humongous environmental challenge, many researchers devoted a considerable effort to partially replacing concrete mix components with waste material derived from glass, plastics, aluminum, wood ash, construction and demolition wastes, or tires. In the current study, a novel effort was conducted to incorporate all the above-mentioned wastes in a concrete mix design and to assess its performance. Five recycled mix designs were explored and based on the concrete mechanical properties derived, an optimum mix was realized. The optimum mix incorporated the following waste percentages: 2% crumb rubber (CR) partially replacing sand, 20% powdered glass (PG) partially replacing sand, 50% recycled concrete aggregates (RCA) partially replacing coarse aggregates, and the addition of 0.5% plastic. The optimum recycled mix was utilized to cast a real-life-size reinforced concrete beam which was compared to a normal mix beam. Land pollution is one type of pollution which includes the desecration of land and contamination of earth due to many pollutants such as wastes, chemicals, sewage, and others. Landfills, by definition, are the dumping of wastes in soil. They are created to be a good solution of discard waste. The wastes dumped include decomposable solid and organic wastes, as well as wastes that are hard to be decomposed like plastics, glass, construction and demolition wastes, industrial wastes, and others2. Disposing of plastic has been an important dilemma for years. Dumping plastic into the environment recklessly lead to the pollution of the land. Plastics in general are not biodegradable, with the presence of sun and environmental factors, plastics degrade into smaller particles that eventually remain in environment without further degradation. According to Jiang, one plastic bottle takes about 1000 years to be degraded3. The solution of Reduce Reuse Recycle (3Rs) was a great idea whose implemented concept was to decrease the impact of disposal of plastic. But although recycling of plastic helped in reducing plastics disposal to the environment by about 29%, yet plastics are still being delivered to landfills in about 18.5% of the whole MSW2. This means that, land pollution problem due to plastic is still unsettled.With the dawn of the twentieth century, plastic evolved into being an essential material being utilized into various products such as bottles, gallons, or bags, etc. This caused the increased in the production of plastic materials due to the increase in demand. According to EPA , municipal solid wastes (MSW) contain a major category for plastic about 12.2%4.Similarly, glass is a material used on daily basis in many shapes and forms. Its demand is increasing constantly, especially in construction, medical field, and others. Glass is considered being a sustainable material since it could be used repeatedly, which means that its lifespan is greater than that of plastic. Yet, after excessive use, it is eventually disposed of in landfills. Same as plastic, glass constitutes about 5% of the MSW. Although it is 100% recyclable, only 31.3% of the total amount of glass found is being recycled5. It can be used as a basic component of fireworks and explosives as it is a good conductor of heat and electricity6. Another alternative is to utilize the aluminum waste in construction.Aluminum is another industrial product that ends up in landfills. It is used in cans, food packaging, construction, industries, and others. Aluminum has the capacity to react with various materials in landfills such as alkaline water releasing large amounts of energy7, motor vehicles are going to reach 1.2 billion representing almost 5 billion tires that are disposed by end of year 2030. Every malfunctioning rubber tire is discarded—not recycled or treated—into landfills. Other than their complex degradation, tires have the potential to burn easily in landfills causing the discharge of numerous toxic chemicals to the soil and air. An alternative of discarding tires in landfills is to utilize crumb rubber (CR) in concrete mix design. CR is produced by shredding and grinding disregarded tires into very small particles.According to Azevedo et al.8. These wastes are dumped in landfills as part of the MSW. The availability of these wastes in landfills has a tremendous negative ecological impact. According to Chemical Engineering Transaction (CET)9, the construction and demolition wastes disposed in landfills cause increased emissions of greenhouse gases (GHG) with a yearly emission level of up to 39% of CO2 per year. Add to that locally, the Beirut Blast of August 4, 2020, has left Lebanon with 800,000 tons of CDW10. Recycled concrete aggregates (RCA) generated from CDW is being used to replace natural aggregates in concrete.Construction and demolition wastes (CDW) are materials formed from residues and debris during the concrete construction or demolition process. EPA promotes and identifies that CDW are resources that might be utilized in new construction developments, thus abolishing the necessity for virgin materials to be extracted and processed11.Wood ash (WA) is the deposit that originates from wood combustion in chimneys, oven bakeries, industries, and others. WA has been dumped recklessly or at best been sent to landfills as waste. WA could be recycled and used in concrete mix as indicated by several researchersAs a result of the various similarities in chemical and physical properties with concrete components, incorporating these wastes in concrete mix design has yielded promising results. The main objective of this research is to combine wood ash, crumb rubber, shredded plastic bottles, powder glass, recycled concrete aggregates, and fine size aluminum flakes in one concrete mix realizing a concrete mix that is adequate for structural purposes. To achieve this objective, five different concrete mix designs incorporating waste materials in variable percentages replacing a certain component of the mix was explored. In this study, WA was used to partially replace cement and sand, CR and PG were used to partially replace sand, RCA to partially replace coarse aggregates, and shredded plastic and aluminum were used as additives in concrete. The mechanical properties of these mixes were compared to a control mix and finally the optimum recycled mix was utilized to construct a real-life size reinforced concrete which was tested and compared to a normal mix beam.12, 91% of all methane and carbon dioxide emissions to the atmosphere are results of open landfills. Air pollution has reached high levels exceeding World Health Organization (WHO) limits, where 91% of population live in areas of high contamination of air13. All these issues are men made. Since none of these issues are being resolved, many serious health problems and diseases arose affecting human and environment where levels of carcinogenic materials are increasing drastically each year. The introduction of waste materials in concrete has been considered a good alternative for dumping wastes in landfills or recycling of these wastes. Although recycling of waste reduced the presence of these wastes in landfills, it required a lot of energy to be achieved producing toxins and impurities. With the main objective of this research being a sustainable environment, the recycling was not considered as an ideal solution. The main advantage of the production of eco-friendly concrete by replacing certain percentages of natural resources, reduced the extraction of raw materials and the production of cement material, as well as the presence of wastes in landfills without releasing any toxic materials or gases to the environment.Pollution has been devastating nature all around the world. It has expanded its roots in every natural resource available in the environment to form land pollution, air pollution, and water pollution. According to Traceability and Verification System for Health Products (TRVST)14. Diverse types of aluminum materials are dumped in landfills. A significant percentage of dumped aluminum material that is being recycled are reused. Yet according to EPA, 2.7 million tons of aluminum materials are present in landfills14. Waste produced during production of aluminum are of different forms depending on the amount of aluminum that it contains. Aluminum flakes are one example of aluminum waste product that is formed after drilling aluminum surfaces like windows and doors. This type of waste is eventually disposed of in landfills. Despite the origin of aluminum waste, when this type of waste is dumped in landfills, chemical reactions can occur specially in presence of alkaline water where toxins and noxious odors and gases are formed15. Some research was performed on including various aluminum materials in concrete mix design to reduce aluminum made waste products from landfills, thus resulting in what is known as Aluminum Fiber Reinforced Concrete (AFRC)16. According to Sabapathy et al.16, aluminum wire scraps were used as fibers in concrete to evaluate the compressive and tensile strength. A total of three grades of concrete and five different fibre volume fractions were evaluated, and a defined looped shape of aluminum fiber was used assuming that the shape, dimension, and length affect the aluminum performance in concrete. It was concluded that the optimum percentage of the looped aluminum in concrete was the minimum percentage of 0.5% resulting in a compressive strength of 21.8MPa, 33.5MPa, and 44MPa for concrete grades of 20, 30, and 40 respectively. Thus, the realized compressive strength was superior to the original concrete mixes. Alternatively, research was conducted based on the addition of aluminum powder to the concrete mix. Kumar and Ramamurthy17 added several grades of aluminum powder in different percentages to mortar mix with a variable water cement ratio of varying. Increasing the dosage of aluminum from 0.25% to 0.50% resulted in a decrease in flexural strength18. In masonry blocks requiring low strength concrete, a compressive strength of 17MPa was achieved by the addition of 0.2% aluminum powder and a 0.5 water to cement ratio19. One of the major issues observed with the addition of aluminum powder was the chemical expansion of fresh concrete ensuing from the reaction of aluminum with alkaline water forming voids and resulting in poor strength concrete20.Aluminum is a material used in several fields and specifically construction. Aluminum waste is present in domestic wastes, industrial wastes, or even in production of aluminum. In domestic wastes, it is available as 1.8% of MSW21. This composition affects the characteristics of plastic which include flexibility, durability, and lightweight. This material is cheap and easy to produce, which makes its manufacturing process faster. Due to the high demand for several types of plastics and the single use products produced, quantities produced have increased. This demand lead to an increase in percentages of disposed plastics in landfills. Other than the land pollution caused by plastic wastes when dumped in landfills, plastics produce chemicals during their degradation process that contaminate the soil. To reduce the environmental impact of plastic waste in landfills, the incorporation of plastic to concrete mixture was a suggested solution. Several studies were conducted where plastic was utilized as an additive to concrete or replacement of aggregates. When adding shredded plastic bottles to concrete, it results in what is known fiber concrete. According to Aseel et al.22, as the percentages of plastic fibers added to concrete increased, the compressive strength slightly decreased, and the splitting tensile strength increased. These results were confirmed again by Irwan et al.23 and specified that the modulus of elasticity decreased as the percentages of plastic added to concrete increased. Foti24 has concluded that because of the improved durability of plastic, concrete has increased resistance to the loads resulting in the reduction in cracks.Plastic is a material known worldwide, accessible to everyone. It comes in different forms, such as water bottles, boxes, household products, and others as it is used in various fields. The chemical composition of plastics is a long chain of polymers formed from short subunits that are joined together by the polymerization process25. Even though a significant percentage of glass containers are being recycled and reused, 7.6 million tons of MSW glass are present in landfills25. As a matter of fact, only 34% of waste glass has been recycled26; consequently, decreasing the amount of disposed glass waste by using glass waste in concrete can be a good solution. Glass powder (GP) replacement of cement can improve the hardened properties of concrete26. Glass is classified as a good additive to concrete without replacing any component of concrete27. PG was used as replacement of sand and resulted in a slight increase in the compressive strength28. Another study29, concluded that a 20% of waste PG replacing sand is an optimum replacement ratio that lead to an improved compressive strength.Glass is a non-crystalline material that is very practical and used worldwide in a versatile manner. In landfills, it constitutes 5.2% of municipal solid wastes (MSW)30. Studies on concrete mixes having substitution of WA for cement concluded that the concrete strength was reduced somewhat as the percentages of WA increased with the optimum percentage to be less than 10%31. Several tests were performed on concrete mixes containing WA replacing sand resulted in slump being reduced substantially while at 5% WA as sand substitute lead to a higher compressive strength than the control mix32. The same study32 indicated that at 5% WA had a lower tensile than control mix concrete while at 20% WA it was greater.The residue left over after the burning of wood and wood products is known as wood ash (WA). About 70% of the wood ash ends up in landfills, where 20% can be used as soil replacement; with a remaining of 10% that is used for various purposes, such as materials for construction, metal recovery, and pollution control. WA has been used as a replacement of several components of concrete. Slump tests performed on fresh concrete mixes with varied percentages of waste WA revealed that mixes containing more wood ash required increased amounts of water to obtain a satisfactory workability33 the compressive strength declined by 94% as the CR replacement of sand increased. Analogous results were achieved by Wang et al.34, they concluded that both the compressive strength of concrete, as well as the flexural strength were reduced as the percentage of crumb rubber increased. Studies by Youssef et al.35 obtained that the optimum replacement of sand by CR was 3.5%; and as this value increased up to 9.5% replacement, the compressive strength decreased by about 37%.The use of CR recovered from vehicles waste tires in concrete mixes has been explored to elevate the adverse environmental effects caused by concrete on natural resources. Heavy metals and other contaminants in waste tires pose an environmental problem when they are deposited in moist soils in a landfill, causing poisons to leak into groundwater. As a result, structural applications of rubberized concrete have garnered consideration as an efficient means of mitigating environmental concerns. According to Park et al.36, RCA derived from CDW can basically replace the natural aggregates of concrete representing around 70% of the total volume of concrete. Thus natural resources are being saved in addition to saving space of landfills and reducing the costs compared with the energy-intensive aggregate exploitations. Other benefits of utilization RCA comprise the decrease of the costs resulted from transferring concrete to the landfill, and moving raw materials to the construction site. All of this in addition to the increase in the life of the landfill resulted from the reduction in the amount of waste dumping. Whereas the useful utilization of RC in concrete is not common, numerous researchers have conducted experimental investigation of concrete mix designs with partial or total replacement of natural aggregates (NA) by RCA. Pavlu et al.37 indicated that RCA properties is directly related to the source, quality of the waste material, percentage ratio of components, and the sieve-fraction of aggregates. According to Veriana et al.38, the ideal replacement ratio of NA by RCA should range betweem 30% and 50%. Furthermore, Nováková and Mikulica36, indicated that a 20% replacement of NA with RCA had no adverse effect on the mechanical and physical properties of concrete and the contrary it yielded an increase of 5.8% in the compressive strength as the result of the existence of residual cement attached to the RCA. According to Tošić et al.39, structural concrete incoporating 50% of RCA resulted into an optimum concrete mix based on environmental, economical, and technical aspects. According to Taffese40, concrete with 10% RCA had a greater compressive strength compared to NA concrete and same splitting tensile strength with 20% RCA.CDW dumped in landfill is a permanent and non-biodegradable waste. These wastes can be suitable for a variety of construction jobs, including road construction, curbs, gutters, bridge foundations, shoulders/medians/embankments, and pavement. RCA derived by crushing CDW can replace natural aggregates. According to Novková and MikulicaIn order to serve the objectives of this research, an experimental program was conducted which included the casting and testing specimens with different variables that were analyzed.In this study, the ingredients that were utilized in the concrete mixes are:Wood ash is a residue resulting from the burning of wood and was collected from a local wood bakery. The grain size of wood ash ranges between 0.13 mm to 0.60 mm. The specific gravity of WA was determined to be 1.70.Crumb rubber consists of fine rubber particles ranging in size from 0.075 mm to no more than 4.75 mm. Crumb rubber is generated after shredding the waste tires and removing the steel debris that are found in steel-belted tires.Fine crushed glass is a waste glass material obtained from a local waste collector that is crushed in the roller and becomes granulated by sieving. The specific gravity of PG was determined to be 2.45.Plastic bottles Fig.  obtainedAluminum flakes Fig.  are wastNatural sand, also known as fine aggregates, is a loose granular substance with grain size of sand ranges between 0.13 mm to 4.75 mm.Medium aggregates any particle greater than 4.75 mm and less than 9.5 mm.Coarse aggregates, also known as gravel, is any particle equal to 9.5 mm and less than 37.5 mm in diameter.Ordinary Portland Cement (PAL 42.5) also known as Cement Type I was utilized.Tap water utilized in the mixture.Water-reducing admixtures were incorporated to reduce segregation and improve the flowability of the concrete. In this case, Sika Visco Crete Techno-15 + which is a new generation, powerful, super plasticizing concrete admixture was used.41 was utilized to conduct sieve analysis on the coarse and fine aggregates. The sieve analysis results for the aggregates are displayed in Fig. 42.ASTM C13643 was utilized in the concrete mixing, casting, curing, and test samples preparation. The first recycled mixture contained all six types of the previously mentioned wastes: powdered glass (PG), crumb rubber (CR), recycled concrete aggregates (RCA), plastic bottles (PB), aluminum flakes (AL), and wood ash (WA). Afterwards, all the remaining tests contained alternating additions of waste to best match the required results. Table The mix design was performed in a pattern to serve the main scope of this research, which is to establish the most eco-friendly structural concrete mix resulting in an optimum mix incorporating the largest quantity of solid wastes. Five recycled mix (RM) design combinations were examined. Six concrete mixes were tested, one of which was a normal concrete mix that did not contain any waste material, used as a control mix (CM) for comparison and analysis of results. ASTM C19244.Slump test according to ASTM C14345.Compressive strength at 7, 28, and 90 days according to ASTM C3946.Splitting tensile strength at 28 days according to ASTM C496For each mix type, cylindrical specimens 150 mm by 300 mm were cast for each experiment, and the following parameters were obtained according to the applicable ASTM standards:Based on the best results obtained a full-scale reinforced concrete was cast using the selected recycled mix design.47.The purpose of testing a full-scale beam was to check the performance of the eco-friendly concrete reinforced beam under load and compare it to a regular reinforced concrete beam. The cross section of the beam is shown in Fig. Strain gauges were placed on the center of each of the two steel bars of T16.Stirrups were placed equally on the 4 steel bars used (2T10 top and 2T16 bottom) on the edges leaving the middle third of the beam unreinforced for shear.The steel cage was placed in steel mold securing the 25 mm cover.Concrete was produced and poured over the setup.Mechanical vibrator was used to assure adequate bonding, eliminating any voids, and smoothing the finished surface.Concrete was removed at 7 days from the mold and cured for 28 days.The steps involved in the casting of the beams Fig.  were:Str48, concrete mix having wastes products as partial replacement of any component of concrete should have minimum compressive strength of 18 MPa after 28 days of curing.A total of six concrete mixes were explored to select an optimum eco-friendly concrete mix that is suitable for structural purposes. Each of the recycled mixes had a different percentages of waste components incorporated in the concrete mix. According to ACI 19.2.1.144. This slump showed that the quantity of water reducer added to the mixture was sufficient enough to give good workability of concrete.The CM yielded a slump of 7 cm, the indication of this test shows that the concrete components have good cohesion together. The slump of the control mix was considered as true slump and the value of displacement showed that the concrete mix is of medium workability, between 50 and 100 mm as specified by ASTM C143RM1 yielded a slump of 110 mm, it showed good workability of concrete: True–High workability. The water reducer added to water in the presence of all the waste products, displayed good results and good cohesion of fresh concrete.RM2 of slump 280 mm, showed over fluidity and workability of concrete. This indicates high water/cement ratio of use of excess water reducer. In this mix, the amount of water was not enough during mixing, so water reducer was added.All the remaining slump tests RM3, RM4, and RM5 yielded a slump of 135, 130, and 140 mm respectively. These tests showed true slump with high fluidity, acceptable percentages of water reducer, and good water/binder ratios.After each concrete mix, a slump test Fig.  was perfThus, the slump tests showed that the inclusion of waste products did not affect the workability of concrete; instead, these products blended perfectly with the main concrete components.The first strength test applied on concrete specimens was the compressive strength. This test gives the results of an essential mechanical property, the maximum compression load that concrete can resist before failing. This test was conducted after 7, 14, and 28 days of concrete curing and results are shown in Fig. The control specimens and RM1 were cast at the same time; the compressive strength test was performed on this mix first to check its performance. The performance of the mixes was checked, and accordingly other mixes were performed and tested.In RM1 tests performed very low results of strength were recorded. Even though plastic and aluminum affect negatively the performance of concrete by decreasing its compressive strength, however, and without doubt, the problem was not with this addition; especially that no replacement of main concrete components was done with these wastes.Based on the results of RM1, to confirm the previous assumption RM2 was performed. After removing plastics completely and reducing the wood ash replacement of sand to 10%, another decrease in the compressive strength was detected. This observation ensured that plastic was not the factor that affected the compressive strength. No conclusion was made at this stage since the results were a bit vague. Not to mention that the slump value of this mix was very high and very workable with no segregation in this mix. The decrease in the compressive strength could be credited to the increase in the amount of water reducer or water/cement ratio.3 of aluminum and the same amount of plastic were added to the mix. By not adding WA, a substantial increase in the compressive strength was observed from average of 3.44 MPa and 2.61 MPa to 8.1 MPa at day 7. This clearly indicated that WA has negatively affected the concrete mix compressive strength. Since its presence in previous mixes was not that effective, it can be concluded that changing the source of wood ash caused a change in its quality, thus affected the concrete mechanical properties.With both RM1 and RM2 achieved results below structural concrete requirements, RM3 was implemented. In this mix, WA was not used and a total of 4.17 kg/mWhile testing the compressive strength of RM1 and RM2, no cohesion between components of concrete specimens was observed. Instead, when load was applied to the specimens, concrete collapsed into small pieces as shown in Fig. 47. At 14 days, the compressive strength of RM1 and RM2 were still below the requirements; RM3 displayed a slight increase in compressive strength. However, better promising results were obtained for RM4 and RM5. Figure From 7-day results, CM, RM4, and RM5 already achieved the above 18MPa being the minimum 28 days compressive strength at required for structural concrete mix, according to ACISplitting tensile is a test used on concrete to determine the mechanical behavior of concrete specimen when load is applied vertically along the length of specimen. Due the dismal compressive strength results for RM1 and RM2, this test was conducted at 28 days for CM, RM3, RM4, and RM5.The control concrete mix attained an average splitting tensile strength of 2.83 MPa. For RM3, RM4, and RM5, displayed an increased values of tensile strength as shown in Fig. Figure For both cases, as the load applied increased gradually resulted in serious cracks being detected Fig. . The loaThe main purpose of this research was to introduce various types of wastes into the concrete mix design leading to the reduction of waste and pollution of the landscape. Some of these wastes were utilized as partial replacement of concrete components where: RCA replaced coarse aggregates, CR and PG replaced sand, and WA replaced sand and cement. Others like PB and aluminum were used as additives to concrete mix.The optimum concrete mix was realized in RM5 which incorporated: 2% CR replacing sand, 20% PG replacing sand, 50% RCA replacing coarse aggregates, and 0.5% PB as additive.The results of the slump test showed that none of the recycled mix affected the slump or workability of the concrete mix. Although several previous research showed that WA ash can be incorporated in concrete as 20% replacement for sand and 5% replacement of cement, the use of WA had displayed negative results. Aluminum flakes used in the mixture had a negative effect on concrete. The expansion of concrete volume was detected in mixes containing aluminum, since aluminum chemically reacted with alkaline water producing voids thus causing the expansion of the concrete and introducing voids.The RM4 recycled concrete mix containing aluminum, PG, PB, RCA, and CR yielded a maximum compressive strength of 16 MPa at 28 days which indicates that it can be utilized for non-structural applications, since the minimum compressive strength of concrete for structural applications is 18 MPa. On the contrary, the optimum mix (RM5) recorded a compressive strength result of about 30 MPa at 28 days. Even though this strength was less than the CM but a higher tensile strength than that of the CM was obtained. It can also be concluded that the addition plastic bottle fibers and aluminum flakes to concrete increased the tensile strength.The RM5 reinforced obviously behaved in a superior fashion when compared to the CM beam. It not only was able to handle a higher load, but it also displayed a superior flexibility capacity in the range of 35% increase in midspan deflection.Achieving sustainability was the main objective of this study. A full-scale beam cast from an optimum mix outperformed the control mix beam. Thus, an eco-friendly concrete mix with reduced amounts of natural raw and the incorporation of waste was realized as an initial step towards a sustainable concrete construction cycle.Based on this study, the followings could be concluded:The authors are not misrepresenting research results and are maintaining the integrity of this research and its presentation. This manuscript is only submitted to this journal. The submitted work is original and have not been published elsewhere in any form or language.


The advantages of rubber concrete (RC) are good ductility, fatigue resistance, and impact resistance, but few studies have been conducted on the effects of different rubber admixtures on the strength of RC and the cracking performance of rubber mortar. In this study, the compressive and flexural tests of rubber concrete and the crack resistance test of rubber mortar were carried out by changing the rubber content and adding expansion agent and retarder in this test. The test results show that the strength of RC decreases with the increase in rubber admixture. At 15% of rubber admixture, the expansion agent and retarder increase the compressive strength and flexural strength of RC the most; the compressive strength increased to 116% (22.6 MPa) and 109% (21.2 MPa), and the flexural strength increased to 111% (4.02 MPa) and 116%. (4.21 MPa). At the same rubber admixture, the expander improves the cracking time of the rubber mortar by about 3 times, and the retarder improves the cracking time of the rubber mortar by about 1.6 times. The BP neural network (BPNN) was established to simulate and predict the compressive and flexural strengths of RC with different admixtures and the cracking time of rubber mortar. The simulation results show that the predicted 7-day compressive strength of RC fits best with the actual value, with a value of 0.994, and the predicted 28-day flexural strength was closest to the measured value, with an average relative error of 1.7%. It was shown that the calculation results of the artificial intelligence prediction model are more accurate. The simulation results and test results show that the expander and retarder significantly improve the strength of RC as well as the cracking performance of rubber mortar. With the rapid development of the economy and continuous optimisation of the building structure, the performance requirements of concrete are improving . Rubber In recent years, expansion agents and retarders have been widely used in various fields of practical engineering. Expansion agents play an important role in both compensating shrinkage and generating self-stress; compensating shrinkage could reduce or even avoid the cracking of concrete due to volume deformation, and adding expansion agents to concrete shows good durability performance . The retIn order to save time, cost, and improve material performance, researchers have predicted the strength of materials based on different machine learning models; the most commonly used method is the back propagation neural network (BPNN). The most important features of artificial neural networks are collective computing, adaptive, excellent fitting ability to highly nonlinear insinuations, and fault tolerance to sample learning. The network can make full use of state information and train the information from different states one by one to obtain balanced convergence weights, which represent the nonlinear mapping relationship of the network. Therefore, it could well find the intrinsic relationship between influencing factors. Han et al.  used theIn summary, there have been a large number of studies on RC, concrete mixed with expanders and retarders, but there are very few studies on the compound effect of adding expanders and retarders to RC, and the prediction of RC using the BPNN is less common in studies on RC. Therefore, this paper investigates the strength of plain concrete, rubber aggregate concrete, rubber aggregate concrete with expander and retarder, and the cracking resistance of plain mortar, rubber aggregate mortar, and rubber aggregate mortar with expander and retarder. Meanwhile, the prediction models of compressive strength, flexural strength, and cracking resistance of rubber aggregate mortar with multiple parameters such as cement, sand, and stone acting simultaneously were established by combining the BPNN approach in order to provide theoretical support for the subsequent research on RC.3; rubber granule adopts rubber with an average particle size of 3 mm produced by Tianjin Kewei Rubber Factory  and an apparent density of 1050 kg/m3, the specific technical indicators are shown in 3; water is ordinary tap water; the expansion agent adopts the UEA-6 concrete expansion agent produced by Beijing Muhu Company ; and the retarder adopts the concrete retarder produced by Hebei Qingjun Chemical Factory .Cement adopts Camel brand P-O42.5 ordinary silicate cement, and its main technical properties are shown in The ordinary concrete, the 5%, 10%, and 15% rubber single admixture of concrete , the 6% expander admixture, with 5%, 10%, and 15% rubber admixture double admixture of concrete , and the 0.1% retarder admixture, with 5%, 10%, and 15% rubber admixture double admixture of concrete  were studied in this paper when measuring the influence of adding an expansion agent and retarder on the mechanical properties. The mix ratio is shown in Mortar was used as the object of study in determining the effect of the admixture of the expander and retarder on the cracking resistance of RC due to the similarity between the cracking properties of concrete and mortar. The ordinary mortar, the 5%, 10%, and 15% rubber-doped mortar , the 5% expander dosing, with 5%, 10%, and 15% rubber-doped mortar , and the 0.1% retarder dosing, with 5%, 10%, and 15% rubber-doped mortar  were studied in the paper. The mix ratio is shown in The test was conducted according to GB/T50081-2002 ‘Test Methods for Mechanical Properties of Ordinary Concrete’ . There w(1)The specimen with a size of 100 mm × 100 mm × 100 mm was placed on the lower plate of the testing machine. The centre of the specimen was aligned with the centre of the lower plate of the testing machine, and the testing machine was started.(2)The ball seat was adjusted to make the contact balanced when the upper pressure plate was close to the specimen. The load was continuously and evenly loaded during the test.(3)We stopped adjusting the accelerator of the test machine when the specimen was close to failure and began to deform sharply until the specimen was destroyed. We also recorded the failure load.The steps of the compression test are as follows:(1)The 100 mm × 100 mm × 400 mm specimen was installed on the press, and the bearing surface of the specimen was the side of the specimen when formed.(2)The support and the pressure surface were in smooth and uniform contact with the cylinder, and the uniform and continuous load was applied.(3)The accelerator of the testing machine was stopped when the specimen was close to failure until the specimen was destroyed. Then, we recorded the indication of the failure load testing machine and the fracture position of the lower edge of the specimen.The test steps of flexural strength test are as follows: The external square inner circle eccentric constraint method and internal circle for measurement were used in the test to measure the mortar cracking time, which could predict the approximate location of cracks and facilitate the observation of cracks. There were 10 proportions and 6 specimens of each proportion in the test. The external square inner circle eccentric constraint method shortened the cracking time of the specimen, improved the test efficiency, and shortened the cycle time. The shape and dimensions of the mould are shown in (1)The test mould was cleaned and the inner wall was coated with oil before the test.(2)The mortar was poured into the test mould and immediately put into the curing room after forming. The surface was wiped twice to facilitate the observation of cracks after 6 h.(3)Crack observation equipment was installed after removing the mould, as shown in (4)The alarm clock time was adjusted to the current time and recorded every 12 h to observe whether the alarm clock stopped. Each group of specimens was observed continuously for 30 days.The test steps of the crack resistance test are as follows:The compressive strength graphs at 7-day and 28-day ages for concrete without admixture, with the expander and retarder at different rubber admixtures, are shown in The compressive strength of concrete decreases with the increase in rubber admixture whether at 7 days or 28 days, as shown by The main reason for the reduction in the compressive strength of RC was the different material properties between rubber particles and cement paste; the rubber used was a polymer organic compound, while cement paste was inorganic. The bond strength between rubber particles and cement paste was low then the rubber particles and cement paste could not be bonded together very effectively. The impact on the strength after the combination of rubber and the expansion agent was the common result of multiple factors. Besides the fact that the rubber and concrete could not be well combined, the other reasons were that, firstly, the admixture of rubber introduced a certain amount of pores inside the concrete, and the more the admixture introduced the larger the number of closed pores there were; the addition of the expansion agent could have made the concrete more dense, thus enhancing the strength of the concrete. Secondly, the rubber itself could reduce the stress concentration caused by the excessive expansion agent to a certain extent and reduce the number of expansion agent micro-cracks when the expansion agent was too large, thus affecting the strength of the rubber-expanded concrete. The impact of the rubber and retarder combination on strength was also caused by multiple factors: in addition to the fact that the rubber and concrete could not be effectively combined, part of the reason was that the main role of the retarder was to extend the setting time of the concrete. The temperature cracks was caused by the hydration heat. The retarder added in the concrete can enhance the strength of the concrete and achieve the effect of low-volume super-retardation which can reduced the temperature cracks caused by the hydration heat of the concrete.The flexural strength of concrete without the admixture, with the expander, and with the retarder at 7 days and 28 days for different rubber admixtures is shown in The flexural strength of concrete decreased with the increase in the rubber admixture, as shown by The cracking times of different mortars are shown in The addition of rubber-retarded the cracking of mortar, as shown by The two reasons for the occurrence of non-structural cracking were mortar shrinkage and mortar brittleness. Introducing anticracking components that abated the two factors in order to improve the crack resistance of mortar was necessary. The reason why mixing rubber was effective in delaying cracking is inseparable from the properties of rubber granules themselves. Rubber granules are a flexible material that can improve the brittleness of concrete and produce larger deformation after internal stress, which could relieve the stress concentration phenomenon and enhance the deformation resistance of concrete. When shrinkage deformation occurred, part of the shrinkage stress was directly absorbed by the internal rubber granules, which could also block the water seepage channels and slow down the rate of drying and evaporation of water, thus delaying the appearance of cracks . The sweThe BPNN is a multilayer perceptron based on error back propagation and usually consist of an input layer, an implicit layer, and an output layer substructure . In this(1)Identify the input, implicit, and output layers.MATLAB is a language software based on network theory, and its main function is to deal with problems between data computation and computer simulation, where the neural network toolbox is a typical network tool function. It is extremely easy and fast to build neural networks using MATLAB . The BPNThe typical structural composition of the BPNN consists of three layers: the input layer, the hidden layer, and the output layer. The structure is shown in (2)Selection of samples and normalisation of sample data.The input vectors were fed through the input layer and then processed by the implicit layer and passed out through the output layer . The str(3)Establishing the BPNN. The two focal functions in the establishment process are:mapminmax: process the matrix by mapping the minimum and maximum values to [−1 1]; the expression and related parameters are explained as follows:The samples in this study were selected from the data obtained from the previous tests on the compressive strength of RC, flexural strength, and rubber mortar cracking time. In order to obtain accurate simulation results, 100% of the sample data were selected as the training sample as well as the test sample. The sample data were normalised to map the sample data to the interval of  or  or other intervals to accelerate the convergence of the neural network and reduce the training time. The data normalisation algorithm is as follows:b.newff, creating a feed forward back propagation network with the following function expression:The mapminmax processes matrices by normalizing the minimum and maximum values of each row to . Then,  = mapminmax  takes X and optional parameters. Then, X means N-by-Q matrix, YMIN means Minimum value for each row if Y (default is −1), and YMAX means Maximum value for each row of Y (default is +1).(4)BPNN parameters setting. In this study, the number of iterations of the designed neural network was 0–1000; the training target error was set to 10-4; and the learning rate was set to 0.01.TFi means the Transfer function of the ith layer. Default is ‘tansig’ for hidden layers, and ‘purelin’ for output layer. BTF means Backprop network training function, default = ‘trainlm’. BLF means Backprop weight/bias learning function, default = ‘learngdm’. PF means Performance function, default = ‘mse’. IPF means Row cell array of input processing functions. Default is {‘fixunknowns’, ‘remconstantrows’, ‘mapminmax’}. OPF—Row cell array of output processing functions. Default is {‘remconstantrows’, ‘mapminmax’}. DDF means Data division function, default = ‘dividerand’.2. The relative error (error) values and the coefficient of determination R2 calculated from the BPNN model are shown in In this study, the evaluation of the prediction results of the BPNN model relies on the relative error and the coefficient of determination R2 was calculated as follows:RAmong them, 2 values of both reached 0.98, which showed a good fitting effect.The predicted values of 7-day and 28-day compressive strength of RC were obtained according to the results of the BPNN model operation, and the predicted values were compared with the measured values measured by the test; the errors between the predicted values of 7-day and 28-day compressive strength and the real values were concentrated within 2%, and the prediction accuracy was high. The two were fitted, as shown in 2 values of both reached 0.97, showing a good fitting effect.The predicted values of the 7-day and 28-day flexural strength of RC were obtained according to the results of the BPNN model operation, and the predicted values were compared with the measured values measured in the test. The 7-day and 28-day flexural predicted values were concentrated within 2% error from the real values, and the prediction accuracy was high. The two were fitted as shown in 2 values reached 0.97, which shows a good fitting effect.The predicted values of cracking time and average cracking time of the first specimen of rubber mortar were obtained according to the results of the BPNN model run, and the predicted values were compared with the actual values measured by the test; the errors of the predicted values of cracking time and average cracking time of the first specimen and the real values were concentrated within 10%, and the prediction accuracy was high. The two were fitted as shown in The prediction model established by the BPNN is much better than the previous prediction by fitting the traditional empirical formula and again verifies the high accuracy of the artificial neural network prediction model, which has established a relationship between the amount of cement, sand, stone, water, rubber, expander, retarder admixture, and the compressive strength, flexural strength, and cracking time coefficient of rubber mortar. Given the amount of cement, sand, gravel, water, rubber, expander, and retarder, the compressive strength, flexural strength, and cracking time of the formulated RC could be predicted by substituting the artificial neural network. The use of neural network to predict the compressive strength, flexural strength, and cracking time of RC was not only efficient, but it also avoids the waste of human, material, and financial resources caused by conventional formulation tests.The compressive and flexural strength of RC decreased with the increase in the rubber admixture. The compressive and flexural strength had different degrees of growth with the addition of an expander and retarder, rubber-expanded concrete, and rubber-retarded concrete compared to RC. The compression–folding ratio of concrete was reduced to make up for the reduction in concrete strength due to the addition of rubber at the same time.The single admixture of rubber in mortar improved the crack resistance of mortar, but the improvement was not great. After the addition of the expander and retarder, the anticracking property of rubber mortar was doubly improved under the joint action of admixture and rubber.The training model based on the BPNN accurately predicted the compressive and flexural strength of RC as well as the cracking time of rubber mortar, where the values reached above 0.97 with a high prediction accuracy. The BPNN showed good applicability to the RC strength prediction problem and could obtain the material proportioning that meets the engineering requirements quickly and accurately verified through the test.


In this research, the durability performance of sustainable concrete with the incorporation of reactive magnesium oxide (MgO) and fly ash (FA) was evaluated. The partial replacement of cement with these two materials is an appealing solution for the construction sector due to sustainability benefits and shrinkage reduction. The incorporation of FA by partial replacement of cement was carried out at 0%, 15% and 30%. The incorporation of MgO in concrete was carried out at 0%, 5%, 10% and 20%. Two types of MgO were used, one from Australia and another of Spanish origin. These two materials were evaluated in terms of their individual incorporation, and then an evaluation was carried out when the two were simultaneously used. In terms of durability, performance losses between 3% and 95% were obtained in all tests . However, over time, the difference in performance relative to the reference concrete tends to decrease due to the slow hydration that characterizes these two alternative materials. It was found that, in most of the tests, no overlapping of the negative effects occurred. In other words, the simultaneous incorporation of MgO and FA caused performance losses lower than the sum of the losses of their individual incorporation. The world population has been increasing exponentially in recent decades. One of the consequences of this population increase will be an increase in the number of dwellings and infrastructures, especially in large cities.2 produced worldwide. More specifically, 7.4% of CO2 comes from cement production. Based on these facts, it is clear that concrete production has a high ecological footprint [The construction industry will play a fundamental role in allowing the correct accommodation of this large number of human beings. The same industry is responsible for the emission of 10% of the COootprint . The useThe cracking of concrete can lead to a reduction in its durability and can also compromise the safety of structures. This can be particularly problematic in regions with harsh weather conditions or high-traffic areas where constant exposure to environmental stressors can weaken concrete. Another problem with Portland cement concrete is the high alkalinity of the mix, which can cause the corrosion of reinforcing steel, leading to potential structural damage. This issue has been of concern in the construction industry for several decades, as the reinforcement is essential for the structural stability of concrete structures. To address these problems, researchers have been studying the use of active magnesium oxide and fly ash as partial replacements for Portland cement.2 emissions [2 emitted for two major reasons. The first one is the lower calcination temperature, since the production of Portland cement involves heating raw materials, such as limestone and clay, to temperatures of around 1450 °C. This process releases large amounts of CO2 into the atmosphere. In contrast, reactive MgO can be produced at much lower temperatures, typically around 750 °C, which results in much lower CO2 emissions [2 over time. The use of reactive MgO can accelerate this process, as MgO reacts with CO2 to form magnesium carbonate. This reaction helps to offset the carbon emissions associated with the production of Portland cement. In this investigation, light-burned MgO was used, characterized by high reactivity, caused by its calcination temperature between 700 °C and 1000 °C [Regarding MgO, it is possible to produce concrete with its incorporation, reducing COmissions . The usemissions ,7. That  1000 °C ,7.3, as seen in Equation (1).Jin and AL-Tabbaa , citing 2, is obtained as the end product (Equation (2)).Mo et al.  stated tDu  presenteThe lower the reactivity of a MgO sample, the slower its hydration. The smaller specific surface area causes more clumping of the particles in a sample, which leads to lower hydration. Jin and Al-Tabba and Mo et al. ,10 reachOne of the most important concrete characteristics is porosity. Given its relevance, several studies have already been conducted. Mo and Panesar  studied Liu et al.  reached Several studies have been conducted on cementitious materials with the incorporation of MgO. In terms of durability, the conclusions obtained by the different authors were clear.Bravo et al.  analyzedOn the other hand, Mavroulidou et al.  studied Pu and Unluer  analyzedIn summary, the use of MgO in cementitious materials leads to worse characteristics in terms of its durability. Analyzing the studies presented, it is clear that the presence of MgO causes an increase in water absorption by capillarity and immersion. The presence of this oxide also causes a greater depth of carbonation in specimens with MgO. Regarding the resistance of chloride penetration, taking into account the variation in the properties mentioned, it is expected that the presence of MgO causes a decrease in this capacity.2 and Al2O3. According to the American Society for Testing Materials [2 + Al2O3 + Fe2O3  is higher than 70%. Physically, it is possible to observe a filler effect, which consists in filling the voids between particles of Portland cement with fly ash particles, because these have smaller dimensions [The use of fly ash is interesting because it allows for its recycling. This material is mainly composed of SiOaterials , the flymensions . Due to mensions ,22.During the first 24 h, fly ash has a retarding impact on concrete hydration. This phenomenon is because the ash needs the glassy fraction to solubilize in order to interact with the calcium hydroxide. After 28 days of age, hydrate growth occurs on the surface of the fly ash particles. The degree of hydration can increase up to 16%, in order to compensate for the lower degree of hydration at the beginning of curing .Saha  demonstr+ and K+) and associated hydroxyl ions (OH−) in the pore solution is mentioned as another reason for this better behavior [Again, Saha  concludebehavior . Sadrmombehavior  reportedAn experimental study by Turk et al.  showed tWith an increasing amount of FA in concrete, it is expected that water absorption by capillarity and immersion will show lower values than those of the reference concrete. The same happens for chloride penetration resistance and carbonation depth, as found in the studies presented above.Analyzing the combination of fly ash with MgO, it was possible to conclude that MgO is insoluble with C-S-H from the hydration of Portland cement and fly ash. Thus, brucite will react with the silica from fly ash, forming a compound called hydrated magnesium silicate (M-S-H) . Dependiw/b = 0.48.Choi et al.  focused 2 [In the same study, the authors also analyzed the carbonation capacity of the different mixes produced at 28, 90 and 180 days of age. The carbonation depths of 65-M0-28 and 65-M5-28 were almost identical up to 180 days of exposure, with a difference of only 4%. On the other hand, 65-M5-360, having been cured for a longer duration, produced a shallower depth of carbonation (15%) than 65-M0-360 from the start. It is then possible to conclude that the carbonation depth at early ages is little affected by the presence of MgO and FA, showing better results at later ages. It is known that an increase in porosity promotes concrete carbonation since it facilitates the influx of CO2 ,30,31.In this experimental campaign, concrete with 0%, 5%, 10% and 20% MgO and 0%, 15% and 30% fly ash was produced. It should be noted that the percentages of incorporation are defined in terms of mass. Furthermore, the study focused mainly on the simultaneous use of these two materials, but this replacement will also be analyzed individually to better understand their combined action.Two different types of MgO were studied, one of Australian origin (MgO-A) and the other from Spain (MgO-S), in order to obtain conclusions on how some specific characteristics of MgO influence the future performance of concrete. Durability-related characteristics were analyzed. An analysis of the concrete in its fresh state was also performed, by studying its workability. In terms of durability, the tests performed were water absorption by capillarity and immersion, carbonation depth and resistance to chloride penetration.Nowadays there is not enough literature to allow the characterization of concrete with MgO and FA in terms of durability. It is important to fill this gap in order to be able to advance in the research of more sustainable concrete. Therefore, this is the main objective of this study. In fact, the scarce research conducted on the combined use of these two materials does not comprehensively assess the durability of these mixes. On the other hand, the evaluation of the use of MgO’s with different reactivity (a low-reactivity MgO and a high-reactivity MgO were used) in these concrete mixes with MgO and FA is also completely innovative.For this investigation, the following materials were used: fine aggregates, coarse aggregates, cement CEM I 42.5R, tap water, MgO and fly ash. No additives were used in this experimental campaign.2 and 24% Al2O3). Two different types of MgO were used, Spanish and Australian, with purities of 85.0% and 98.8%, respectively. In terms of specific surface area, MgO-S had 4.9 m2/g, while MgO-A had 51.2 m2/g. The reactivity was 3544 s and 14 s for the Spanish and Australian MgO’s, respectively. Liska et al. [Portland cement CEM I 42.5R was produced by Secil . In terms of natural aggregates, two types were used: coarse aggregates  and silIn Following a methodology presented by Nepomuceno et al. , the comThe only change in the composition of the other mixes is the amount of each binder, according to defined and explained percentages. In total, 21 concrete mixes were produced: reference concrete (RC); mixes with replacement ratios of 5%, 10% and 20% MgO-A and MgO-S, by mass; mixes with incorporations of 15% and 30% fly ash, by mass (with or without MgO). Each mix is identified as Cx/y:FA/MgO-A or Cx/y:FA/MgO-S, where x is the amount of FA and y is the amount of Australian or Spanish MgO, respectively.It was decided to divide the experimental campaign into three phases. Firstly, the different materials that constituted concrete were evaluated. Then, the concrete mixes were analyzed in their fresh and hardened states.In order to classify the different mixes in terms of durability, the tests previously mentioned were performed. The water absorption by capillarity was evaluated at 28 and 91 days, in 3 specimens, according to LNEC E-393 (1993) . Water aBy increasing the incorporation ratio of reactive MgO, the consistency of the mixes tended to decrease. Therefore, it was necessary to increase the water/binder ratio in the mixes as reactive MgO increased to maintain the target consistency, as observed in Firstly, the results of water absorption by capillarity at 28 and 91 days for concrete with the incorporation of MgO are presented in As expected, the capillarity values at 28 days are higher than those at 91 days. An increase of 37% is observed in C20:MgO-A, relative to RC, at 28 days. However, this increase is only 23% at 91 days. Choi et al.  reached Analyzing 2, 60% RH and 23 °C temperature is provided. It is immediately clear that with the incorporation of MgO and FA, the carbonation depth increases. In fact, when the ratio of these materials used in the mixes increases, the carbonation tends to present higher values. This phenomenon was expected due to several reasons. First, the increase in the water/binder ratio in the mixes with MgO and/or FA causes a more porous matrix.In 2, in which interaction between them would lead to a decrease in the progress of carbonation. In addition, according to Gonçalves et al. [2, which exhibits a pH level of ~12.5, and a higher amount of Mg(OH)2, with a pH of ~10.5, means that the overall pH level lowers, thereby showing an increased rate of carbonation according to the phenolphthalein test. This, together with the existence of a more porous microstructure, relative to RC, will be quite coherent justifications.On the other hand, the partial replacement of Portland cement causes lower production of C-S-H and Ca(OH)s et al. , the decThe MgO from Spain shows worse results than the one from Australia. As previously mentioned, this is because the lower specific surface area of the MgO-S particles causes greater porosity, facilitating the progression of carbonation to greater depths. This can be seen in Knowing that the presence of FA leads to an improvement in carbonation capacity ,30, it sThe worst results were obtained when 20% MgO was used, with an increase of 100% in the chloride ion penetration coefficient relative to RC. As with the previous properties, the theoretical value expected for the combination of MgO and FA is substantially higher than the value obtained in the laboratory, as shown in Several studies have been carried out comparing chloride ion penetration with water absorption by capillarity. Ferreira  concludeThe linear relationship between the carbonation depth and the chloride diffusion coefficient was also analyzed, at 28 days, and it can be observed in It is important to compare the compressive strength with the different durability properties analyzed in order to understand whether there is a relationship between the different properties. For the reference concrete, a compressive strength of 44.2 MPa was obtained at 28 days, and a compressive strength of 48.3 MPa was obtained at 91 days. In Regarding compressive strength, it is clear that there is a decrease in strength capacity in concrete with partial incorporation of MgO and FA. In fact, the greater the amount of MgO and FA incorporated, the greater the observed reduction in this capacity compared to the reference concrete. At 28 days, there were decreases of between 23% and 60% in the compressive strength of ternary mixes compared to RC. However, at 91 days of age, this decrease ranged only between 13% and 40%, proving the better behavior of these concrete mixes with the progress of curing time.It is clear that the decay in the mechanical capacity of concrete is accompanied by worse results in terms of durability. The simultaneous presence of MgO and FA in concrete composition leads to worse results in all durability properties studied. As the amount of these materials increases, a worse behavior of ternary mixes is also observed.It is concluded that the mechanical and durability properties present similar behavior in concrete with MgO and FA. This phenomenon is proved by verifying that with increasing amounts of MgO and FA in the cement matrix of concrete, worse compressive strength results are obtained. The same was found for durability.This research served to study the influence, in terms of durability, of concrete with partial incorporation of MgO and fly ash. It was possible to analyze the corresponding variations when Portland cement was replaced with 5%, 10% and 20% MgO and/or 15% and 30% fly ash. In almost all the properties, worse results were obtained with the presence of one of these materials, or both, relative to the reference concrete.It was also found that Spanish MgO generally presents worse results when compared to the Australian counterpart. This was due to its lower specific surface area and, consequently, to its lower reactivity. These characteristics increase the porosity of the cement paste. It is well known that the porosity of the cement paste is of vital importance in determining the durability behavior of concrete.By incorporating MgO and FA in the constitution of concrete, it is concluded that as the amount of these two materials increases, the capillary absorption capacity also tends to increase. For mixes with simultaneous incorporation of MgO and FA, there was an increase in all mixes produced, ranging from 3.7% (C15/5:FA/MgO-S) to 24.3% (C30/10:FA/MgO-S), at 28 days of curing age.A similar behavior was detected in the water absorption by immersion capacity at 28 days. The combined incorporation of the two materials caused worse results. In individual terms, the presence of only 15% FA causes a 26.5% increase in water absorption capacity. Concrete with 30% FA and 20% MgO-A shows very similar results, with an increase of 64% and 65% in this property, respectively, compared to conventional concrete. In the combined use of MgO and FA, the best result was obtained for the mix C15/5:FA/MgO-S, with an increase of 39.5% relative to RC.Observing the results obtained for carbonation depth, similar results were obtained. The worst result was observed for C20:MgO-S, with an increase of 160% in carbonation depth at 91 days. However, the use of FA originated an improvement in comparison to RC. The lowest carbonation depth value was obtained for the mix RC30:FA.As expected, with the incorporation of MgO and FA, the chloride ion migration coefficient increases. The worst results were obtained when 20% MgO was used, with an increase of 100% in the chloride ion penetration coefficient relative to RC. As previously mentioned, with the increase in the amount of MgO and FA in the cement matrix of concrete, there is an increase in the penetration of chloride ions, for all mixes, with the best value being reached when using 30% FA and 5% MgO, causing an increase of 35.4% in this property relative to RC.By studying the compressive strength at 28 and 91 days, trends similar to those observed in the durability properties were found. The partial replacement of OPC causes a decrease in the mechanical capacity. Accompanying this decrease is a worse durability behavior of the non-conventional concrete. It is thus concluded that the presence of MgO and FA in concrete negatively affects the mechanical and durability characteristics of concrete.Finally, one of the most important conclusions was that in none of these properties was there total overlapping of the negative effects. In the results obtained, an improvement is obtained when FA and MgO are combined, relative to the expected theoretical result. The theoretical value corresponds to the sum of the individual effects of each material. It was observed that in all the analyzed properties, the results obtained in ternary mixes were better than the expected theoretical results. This improvement was especially observed in the carbonation depth and resistance to chloride ion penetration.Comparing the ratio of OPC replaced with the increase in the studied properties, it is possible to draw some conclusions. Only in the water absorption by capillarity, decreases with the use of MgO and FA, relative to RC, lower than the ratio of incorporation of these materials in the different mixes were observed. For example, in the mix C30/20:FA/MgO-S, the simultaneous incorporation of MgO and FA , originated an increase of only 20% in the water absorption by capillarity relative to RC. In the remaining properties, the opposite phenomenon was found. The exception is the mix C30/5:FA/MgO, where low values of carbonation depth were obtained.In conclusion, it is clear that the combined use of MgO and FA shows better results than would be theoretically expected. However, except for water absorption by capillarity, the OPC replacement ratio is higher than the observed variation. The simultaneous use of these materials seems to work better, but more studies are needed to find the ideal incorporation ratio that could lead to better results. In this research, the incorporation of 15% FA and 5% MgO in concrete seems to be interesting. On the other hand, the replacement of 50% OPC seems excessive.The practical benefits of using reactive magnesium oxide and fly ash as partial replacements for Portland cement in concrete production are significant. First and foremost, these materials are cost-effective and readily available, making them an attractive option for builders and engineers seeking to improve the sustainability and durability of their structures. Additionally, the use of active magnesium oxide and fly ash can improve the workability of concrete, making it easier to pour, mold and shape into the desired form. This can be particularly beneficial in construction projects where intricate or complex designs are required, such as in the construction of high-rise buildings, bridges and other infrastructure. From a maintenance perspective, the use of reactive magnesium oxide and fly ash can also improve the longevity and safety of concrete structures. By improving the resistance of concrete to cracking, structures can be expected to last longer and require less frequent repairs and maintenance.The use of reactive magnesium oxide and fly ash as partial replacements for Portland cement in concrete production shows promising results. However, further research is needed to fully explore and optimize the potential of these alternative materials.One area of further research is to investigate the performance of concrete mixes containing different ratios of reactive magnesium oxide and fly ash. This would help to identify the optimal mixture for achieving maximum performance and sustainability while maintaining cost-effectiveness. In addition, the long-term durability of concrete structures containing reactive magnesium oxide and fly ash should be studied. This would involve testing the performance of these structures under different environmental conditions over an extended period of time. This information would be valuable in determining the maintenance requirements of concrete structures containing these alternative materials. Another area of further research is to study the effects of using reactive magnesium oxide and fly ash in combination with other sustainable construction materials, such as recycled aggregates, in order to further reduce the environmental impact of concrete production. These research topics will be crucial to optimize the use of these materials in concrete structures with maximum performance, sustainability and cost-effectiveness for growing cities and communities.


Antimicrobial resistance (AMR) is a growing global concern, with the most significant health and financial implications for low- and middle-income countries. Due to irrational and inappropriate use, AMR is rapidly increasing in Bangladesh, especially among low-income urban populations. This study explored the factors for antimicrobial resistance among ≤ 5 years children in low-income urban Bangladesh.From February 2018 to April 2019, we did quantitative and qualitative assessments of antibiotic use among urban ≤5-year children. We conducted a cross-sectional survey among 626 low-income urban ≤5-year children's parents in four cities in Bangladesh. We used a semi-structured questionnaire to collect data related to antibiotic use through face-to-face interviews. We also conducted eight focus group discussions among the parents to gather in-depth information on antibiotic use to treat their children. Bivariate and multivariate analysis was done to see the causes and associated factors.The study identified that 62.9 % (394/626) of parents used antibiotics last year to treat their children. More than half (52.7%) of the parents bought antibiotics from local drug stores without a prescription. 46.5% (291/626) of the parents stopped antibiotics soon after the symptom disappeared, and 62.6% used leftover antibiotics for similar symptoms. However, 82.9% of parents opined that qualified physicians' advice is important to treat children with antibiotics. Inappropriate antibiotic use was significantly associated with participants' education (p=0.02), family income (p=0.01), and profession (p=0.04). Qualitative investigation revealed the convenience of getting treatment and medicine from the drug store, the financial burden to buy the full course, the distance and waiting time at qualified physicians, and parents' inadequate knowledge were identified as the key causes of irrational antibiotic use.Pattern of Antibiotic Consumption among ≤5-Year Children in Low-Income Urban BangladeshIntervention packages are required to improve parents’ knowledge and awareness on the rational use of antibiotic. Strengthening the health system could enhance the optimum use of antibiotics and combat antibiotic resistance. Antibiotic dispensing, prescription, purchase, and selling policy required with enforcement of the policy to reduce AMR.All Authors: No reported disclosures


Background: Western State Hospital (WSH) is an 800-bed, state-owned psychiatric hospital in Washington State which services individuals in 20 counties. WSH provides services and inpatient treatment to patients referred via behavioral health providers and/or the civil court system. Because many patients are admitted with serious, long-term illness, WSH also provides primary care and addresses infectious syndromes encountered in admitted patients. In January 2016, WSH officially began their antimicrobial stewardship program (ASP). In 2017 WSH joined the UW Center for Stewardship in Medicine (UW-CSiM) to grow and optimize their ASP. Methods: The lead pharmacist at WSH participated in weekly hour-long education and tele-mentoring sessions through the UW-CSiM program. Educational materials were adapted from UW-CSiM didactics and delivered to providers during regular meetings and grand rounds. Daily pharmacist led prospective audit with feedback was conducted. Antibiotic use data were collected and measured by days of therapy (DOT) per 1000-patient days from pharmacy dispensing records from 2015 to 2022. Results: From 1/1/15 to 12/31/22, there was a consistent trend of decreasing antibiotic consumption annually. In particular, antibiotic use decreased by over 65% ranging from 35-43 DOT per 1000 patient-days in 2015 to 9-11 DOT per 1000 patient-days in 2022 . This translates to approximately 1000 antibiotic days of therapy in 2015 and 200 days of antibiotic therapy in 2022. As of 2022, the two most common antibiotics used were cephalexin and sulfamethoxazole/trimethoprim Conclusion: Although treating infections is not a principal focus of a psychiatric hospital, patients receiving care in inpatient psychiatric facilities do experience common infections and receive antibiotics during their stay. At WSH, initiation of an antimicrobial stewardship program was associated with sustained decrease in total antibiotic DOT over 7 years. These data highlight the impact of tele-education and tele-mentoring in infectious diseases and antimicrobial stewardship as a path to build a successful antimicrobial stewardship even without formal infectious diseases training. Our single center experience at a large psychiatric hospital demonstrates the use of antimicrobials in these facilities and the opportunity for a large impact of an antimicrobial stewardship program in inpatient psychiatric facilities.Disclosures: None.


Pesticides help produce food for humanity’s growing population, yet they have negative impacts on the environment. Limiting these impacts, while maintaining food supply, is a crucial challenge for modern agriculture. Mitigation measures are actions taken by pesticide users, which modify the risk of the application to nontarget organisms, such as bees. Through these, the impacts of pesticides can be reduced, with minimal impacts on the efficacy of the pesticide. Here we collate the scientific evidence behind mitigation measures designed to reduce pesticide impacts on bees using a systematic review methodology. We included all publications which tested the effects of any pesticide mitigation measure (using a very loose definition) on bees, at any scale , so long as they presented evidence on the efficacy of the measure. We found 34 publications with direct evidence on the topic, covering a range of available mitigation measures. No currently used mitigation measures were thoroughly tested, and some entirely lacked empirical support, showing a weak evidence base for current recommendations and policy. We found mitigation measure research predominantly focuses on managed bees, potentially failing to protect wild bees. We also found that label-recommended mitigation measures, which are the mitigation measures most often applied, specifically are seldom tested empirically. Ultimately, we recommend that more, and stronger, scientific evidence is required to justify existing mitigation measures to help reduce the impacts of pesticides on bees while maintaining crop protection. The majority of modern agriculture relies on pesticides to protect yields . So, whiPesticides can cause harm to the environment in many ways, including threatening bee populations . Bees poMany governments are making considerable efforts to shift away from widespread pesticide usage, through guidance, incentives, and pressure . One keyHow pesticides are used is critical in determining their environmental toxicity. For example, an insecticide applied to a tree in flower could be damaging to bees and other pollinators , while aMany mitigation measures are already mandated on the pesticide product label or in governmental guidance documents . Within Given the scale and impact of pesticide usage, it is important that mitigation measures used are effective . While mWe searched the literature for any publications presenting evidence on the efficacy of any pesticide mitigation measure in reducing the impacts of the pesticide on bees. We define a mitigation measure very broadly as “actions taken which reduce the potential negative effects of a pesticide application, while still allowing the application.” We define an impact as any measurable effect on bees covering all scales from individual bees through to the population level. A Web of Science Core Collection search was undertaken in October 2021 using the PRISMA framework . An initThe following terms were used in a Topic, Title, and Abstract Search for the main search:AND(honeybee OR bumblebee OR bee OR bees)AND(pesticid* OR herbicid* OR fungicid* OR adjuvant OR co-formulant OR coformulant OR insecticide OR molluscicide OR (plant protection product) OR agrochem* OR (agro-chem*) OR agrichem* OR (agri-chem*)))After screening the results of this high-yield search and identifying the range of mitigation measures tested in the literature, a supplementary search protocol was used. Here 16 narrow, low yielding, searches were used to supplement the main search. Not all mitigation measures could be included in a supplementary search as the terms to parameterize them were too vague, that is, crop type. Narrow searches were based on mitigation measure identified from the results of the initial broad search alongside other search terms based on the FAO Pesticide Registration Toolkit  and publOur primary inclusion criteria were that a peer-reviewed publication presents a study(ies) where a measure is taken to reduce the impact of a pesticide application on bees, and the efficacy of this is recorded. We define what a measure taken could be very broadly and included measures of ambiguous relevance. We define the efficacy of the measure as any measurable impact on the bees tested . Beyond this broad definition of a measured impact, we also include any publications that measure a change in pesticide residues in a matrix that has been collected by bees  to facilitate a quantitative comparison. The Publications by Topic section lays out the key findings such that they may be judged qualitatively. Some publications test multiple species, substances or topics, and thus can be double counted in the figures and text. The comparisons of research quantity presented in the figure legends used chi-squared goodness-of-fit tests, all assumptions were met.Other evidence sources do exist, which provide information on the efficacy of mitigation measures, without directly experimentally testing them. We acknowledge that their exclusion underestimates the level of knowledge we have underpinning mitigation measures. Evidence from regulatory testing, both toxicity and residue level, and evidence submitted to regulatory bodies may not be captured in this review if not published through a peer-reviewed scientific journal.Apis mellifera was most tested, although 4 publications tested Apis florea.Thirty-three publications were found that met our criteria, with one further publication identified from our knowledge of the literature. Of these publications, 14 were from the United States, with less than 5 coming from every other nation represented. Twenty-nine publications tested on honey bees, while just 5 tested on bumble bees, and just 3 on all other bee species see . Among hThe most common mitigation measure tested was repellents designed to repel bees from visiting recently treated crops, with 12 publications. Eight tested changes to how the pesticide is applied, with 2 testing things that can be done after the pesticide is applied (both irrigation). Four tested alternative forage (food and water) and another 4 tested interventions for managed bees. Three tested changes to the conditions when the pesticide is applied (season and humidity), and finally one tested the application of a herbicide to prevent exposure to other pesticides see .n = 16), while 7 others used a spiked food source. Seven publications used seed treatment dust, 3 used cubes of agarose gel, 1 used a soil drench, and another used spiked irrigation liquid. Nearly all publications were agriculturally focused (n = 26), with just one from horticulture, while 7 publications did not specify their focus.Just 10 publications measured residue data in relation to the mitigation measure. Where publications mimicked pesticide application, how they mimicked it varied considerably. Most used a spray , and there were just 4 fungicides, 1 herbicide, and 3 combination exposures. Not all experiments applied substances to a crop, but those that did were very varied. Seven publications used corn, while cotton and oilseed rape were next, both with 3 publications each, as well as several other crops.Insecticides were the most common active ingredients studied .Irrigation is used to keep crops well-watered, but it can also move pesticide residues down into the soil. Just 2 publications have tested this in relation to pesticide impacts on bees. Insecticide labels often recommend removing flowering weeds from the area to be sprayed e.g.,  to preveBombus terrestris colonies. Many landscapes are dominated by agriculture, and such monocultural landscapes can lead to more limited diets for pollinators. Two publications tested the impacts of supplemental forage for reducing the impacts of a pesticide application on bees. Bombus impatiens.Interventions can be made when managed bees are set to be exposed to pesticides, with the aim of directly mitigating the impacts. The extreme example of this is the use of medicinal compounds that directly counteract the pesticide itself. Melipona scutellaris, had lower mortality when exposed to a neonicotinoid insecticide if they also had an uncontaminated water source. A series of publications found that honeybees supplied with supplemental water had higher survival when exposed to pesticide applications in nearby fields  and irrigation after application. However, a label recommendation or stipulation to modify either of these 2 parameters to protect bees would be confusing to farmers as it may contradict recommendations from equipment manufacturers on how to achieve an effective spray.In a similar vein, while high humidity was found to cause additional toxicity from seed treatment dust , it woulSeveral technological solutions to reduce environmental impacts of pesticides have been developed i.e. beneath canopy sprayers , dust-reConversely, while some measures were found to be effective, their implementation may have wider environmental consequences that do not justify their use. One of these is herbicide application as a means to reduce bees insecticide exposure . HerbiciAnother mitigation measure of contentious value is medication for managed bee species to reduce the impacts of insecticide exposure . This poApis bees are also only assumed and may not be relevant for many species that do not collect water.Alternative forage was tested in 2 publications on alternative food forage and 2 on alternative water forage. The promotion of supplemental forage for pollinators and wildlife in general is a well-supported notion for biodiversity conservation , and oneDust from seed treatments was an exposure route in many publications. No reasonable measure to reduce its impact on bees was supported by multiple publications, although one seed drill design was reported to be promising . The mosOne topic that dominated the literature (12/34 publications) was the use of repellent additives to pesticide sprays, with the potential to be effective in protecting wild and managed bees. Several promising chemicals were found as well as several methodologies for developing and validating their efficacy. The academic evidence is now limited by 2 factors, full-scale field trials and formulating constraints, which could also be addressed by the industry. Formulations can be constrained by difficulties mixing different substances, but as a range of chemicals have been found effective repellents it is unlikely none will be compatible with modern formulations.Debate exists over how long the repellence would need to be. In general, mitigation measures would benefit from an explicit understanding of what exposure to pesticides they are trying to avoid, direct overspray or longer-term residues. Residues of pesticides can remain in the nectar and pollen of crops, and the environment more broadly, for long time periods after application and pose a risk to bees in addition to direct spray . MeasureA notable omission from the literature is whether restrictions to the time of day a pesticide can be applied are effective. This is a common label restriction for many insecticides toxic to bees, with label language such as “If crop is to be sprayed during flowering, then spray in the evening or on a cloudy day when bees are not active in the crop” e.g.  althoughApis bees , with little or no focus on other pesticide groups . HoweverTo conclude, the evidence for currently used mitigation measures is sparse with several major knowledge gaps. Of prospective mitigation measures, many were reported to be effective, albeit with a small evidence base. Mitigation measures are but one tool that can be used to reduce the effects of pesticides on bees, and others should be explored also. In addition, whether mitigation measures target risks of over spray and/or residues needs further consideration. Far too much of a focus has been on measures to protect managed bee species specifically or using managed bee species to test measures, which would benefit all bees. For honey bees, a range of effective well-supported measures exist, such as direct interventions to shield honey bee hives from pesticide exposure. Repellent additives are a promising line of research, ready to be picked up by industry. Technological solutions like novel sprayer designs and seed treatment dust prevention are being trialed, with only limited success, but should be pursued further. While mitigation measures may not eliminate environmental harm, they have the potential to reduce it until farmers can be supported in moving away from pesticide-reliant agriculture. Ultimately, research on mitigation measures is a field ripe for further research which could substantively reduce how dangerous pesticides are for bees without serious consequences on pesticide efficacy.toad118_suppl_Supplementary_MaterialClick here for additional data file.