Ultrasonic measurements are used in civil engineering for structural health monitoring of concrete infrastructures. The late portion of the ultrasonic wavefield, the coda, is sensitive to small changes in the elastic moduli of the material. Coda Wave Interferometry (CWI) correlates these small changes in the coda with the wavefield recorded in intact, or unperturbed, concrete specimen to reveal the amount of velocity change that occurred. CWI has the potential to detect localized damages and global velocity reductions alike. In this study, the sensitivity of CWI to different types of concrete mesostructures and their damage levels is investigated numerically. Realistic numerical concrete models of concrete specimen are generated, and damage evolution is simulated using the discrete element method. In the virtual concrete lab, the simulated ultrasonic wavefield is propagated from one transducer using a realistic source signal and recorded at a second transducer. Different damage scenarios reveal a different slope in the decorrelation of waveforms with the observed reduction in velocities in the material. Finally, the impact and possible generalizations of the findings are discussed, and recommendations are given for a potential application of CWI in concrete at structural scale. The assessment of the residual safety and durability of reinforced concrete structures  is vital for the efficient planning of retrofitting strategies for modern-day infrastructure networks. Ultrasonic measurements are frequently used to monitor the structural health of such concrete structures with the objective of detecting changes as early as possible before devastating damages occur.Due to multiple scattering effects in heterogeneous media, the coda wave, i.e., the trailing diffuse part of wave signals, is especially sensitive to small changes in the apparent seismic velocity ,2. In adry (CWI)  has beenir rocks ,7, in coir rocks ,9. Furthir rocks .In addition to ultrasonic laboratory experiments on different-sized concrete specimen, numerical simulations have been used to explain and understand the coda signal and its sensitivity to various damage geometries ,11. In tconcrete . In thisTo study the effect of different damage scenarios on ultrasonic wave propagation and the analysis with CWI, simulations of the full elastic seismic wavefield were performed using a rotated staggered-grid finite-difference scheme . All simhttps://pycmg.readthedocs.io/en/latest/ accessed on 15 July 2021.At the mesoscale, the internal material structure of concrete is characterized by a large volume fraction of aggregates (up to 60–70%) of different sizes, embedded into a mortar matrix. Subjected to an external load, the mesoscopic heterogeneity in concrete contributes to highly complicated stress- and ultrasonic wave fields. Especially when interacting with the initial defects at finer scales, it results in a complex damage process ranging from diffuse microcracking to localized fracture . Thus, tIn general, a concrete aggregate can be characterized by its multiple faces, sharp corners/edges, and multiple non-convex surfaces. In our work, aggregates are modeled by means of irregular polyhedrons with concave depressions. The generation of a virtual aggregate involves the reduction of an initial cuboid to the polyhedron by applying multiple random cuts tangential to an imaginary inscribed ellipsoid. The ellipsoid geometry is a function of the maximum size and the elongation ratio (ratio of the longest dimension to the shortest dimension). The random orientation of an aggregate is realized by applying rotational transformation with respect to the global axes and the concave depressions are introduced in terms of a 2D Gaussian surface at random locations lying on the surface of the inscribed ellipsoid.After each aggregate or grain is generated, the next step is to embed it into a prescribed hosting mortar matrix . The main objective of the assembly step is to randomly pack aggregates that follow the statistical particle size distribution (PSD) of concrete, while fulfilling the non-overlapping condition between aggregates. The packing strategy begins with the pre-processing of input packing parameters such as the grading curve of concrete, and the total volume fraction. Each particle family is sorted according to their size and the largest particles are placed first, followed by smaller particles until the target volume fraction of each size is reached. The current aggregate is successfully embedded into the mesostructure only if it does not intersect with other aggregates as well as the number of attempts does not exceed an a priori defined value. The mesostructure is periodic. This is achieved by assembling the part of the aggregate lying outside the surface of the mesostructure domain to the opposite surface. This feature allows the generation of large-sized concrete models, for instance, at the structural scale.In the current study, we considered three concrete mesostructures with three different grain size ranges. The goal is to take into account the influence of grain size on the simulated Coda signals with increasing damage level. The three samples are denoted as sample 0, sample 1, sample 2  generateWith the concrete mesostructures at hand, we proceed to model damage of concrete using the Discrete Element method (DEM). In DEM, a granular material  is described as a packing of DEM-particles that are linked together by cohesive frictional forces. Within the material, the induced forces are transmitted via a contact network between particles and the dynamics of these particles is governed by Newton’s second law . The conThe inter-particle modeling in the DEM approach based on  is brief©XeonR©Gold 6148 CPUs running in parallel at The modeling of damage in concrete begins with the generation of a random densely packed ensemble of 661,830 DEM-particles with radius of 0.8mm  Left. Ne=0.3m in  of the vested in . Followiested in , DEM uni‘WooDEM’ . The sofd of particle i is evaluated by averaging the damage variable over all cohesive contacts associated with that particle. Particles/voxels with parameter of value 0 are in undamaged stage, while At each time increment, the damage parameter For each numerical sample, ten mesostructure snapshots at different damage levels are extracted for the wave propagation analysis. To simulate the ultrasonic wave field, the mesostructural models for concrete specimen described in the previous section are assigned appropriate parameters for P- and S-wave velocity and density. These parameters for the initially undamaged state are listed in d. This first set of models is denoted as “macro+microcrack” for the remainder of this study.The virtually generated mesostructure models  are subjected to tensile loading. Each of the samples 0, 1 and 2, subjected to uniaxial tension was analyzed by the DEM up to failure, covering the complete damage regime, from the intact state, to an initial diffuse growth of microcracks up to complete failure of the sample. For the wave propagation analysis described in the next subsection, local elastic velocities are assigned at the corresponding locations according to the local damage level A second set of models has been generated for samples 1 and 2 in which, for the wave propagation simulations, diffuse damage, i.e., damage levels corresponding to a lower-level load ”) and the grain phase (“diffuse damage (grains)”).In the following sections, the models described above are denoted as their aggregate compositions  plus their history of damage .Ultrasonic wave field simulations were performed with a model size of .1m×0.1m . The conIn this study, a rotated staggered-grid finite-difference scheme  is used The spacing between adjacent points of the evenly spaced finite-difference grid is To simulate the typical decline in amplitudes with time observed in the coda wave of ultrasonic measurements, a homogeneous intrinsic attenuation has been applied. At the central frequency of the source signal, the attenuation is For all simulations, a single source and a single receiver are used. Source and receiver are located at the center of the x-y-slice and separated in z-direction by 0.3m a. The so0.3m b,c. The velength .For the analyses in this study, the xx- and zz-component of the stress recorded at the receiver position are averaged d,e and uSince transducers have a discrete physical size, preliminary tests have been performed with implementing multiple sources in a localized area. The results did not show a significant difference as compared to the implementation of a single point source. Therefore, sources are implemented as point sources in this study.t representing the discrete simulation steps performed using the input models from each of the sets described in the previous section, T is the total recording time per simulation step and Following the approach outlined in , the strectively :(1)up(t′field up :(2)CC Diffuse damage implemented by reducing velocities in the complete sample and (2) localized crack opening during increasing tensile loading computed by the DEM model. In the following, results from these scenarios are investigated separately first and then compared.To simulate velocity changes corresponding to diffuse damage, i.e., induced by temperature or moisture variations, the P-wave and S-wave velocities have been reduced stepwise and the CWI workflow has been applied to every step. As described above, two scenarios are investigated in what follows: Reduction of velocities only in the matrix and reduction of velocities only in the grains.The velocities were manually reduced in six discrete steps. A reduction in the velocities of the matrix phase results in observed velocity changes  changes . This diA significant portion of the grains in sample 0 are smaller than 10% of the dominant wavelength used here  which haThe numerical models of the concrete samples have been provided from the DEM simulations at different levels of uniaxial tensile loading and used for wave propagation simulations. The different loading levels correspond to different levels of damage and different locally reduced wave velocities of the mortar matrix.t , a steep increase of In this set up with a single source and a single receiver, the location of the macrocrack (closer to the source or closer to the receiver) produced nearly identical results due to the source-receiver reciprocity of the elasto-dynamic wave equation.In the previous section, the capability of CWI to discriminate between different damage scenarios has been demonstrated. Further confirmation of the results of this study could be achieved by measuring temperature and moisture simultaneously with acoustic emission signals, i.e., with a system such as reported in . AlthougThe used approach to create mesostructural models has been demonstrated to produce very realistic results . SimilarIn the previous section, the recording length was fixed to  and 3ms . For com and 3ms . This isThe figure also shows that a recording length of In this study, the complete signal is used for the analysis. In practice it may be beneficial to exclude the first arrival and/or investigate different parts of the Coda signal separately to recover the velocity changes at different distances with respect to the transducers.In the previous simulations, vacuum boundaries are assumed around the sample to mimic finite-sized concrete specimen. If larger structures are monitored , the ultrasonic wave field travels only through parts of the structure. Depending on the transducer positions, the wave field is not reflected at the boundaries. Therefore, absorbing boundaries approximate this particular situation more adequately. Simulations for sample 2 with suppressed microcracking and the diffuse damage scenario in the mortar matrix are repeated with absorbing boundaries. It is hardly possible to distinguish the different damage scenarios . The decFurther studies need to be performed to enhance and update the CWI workflow to make it suitable for large-scale structures. Preliminary ideas involve the use of a set of optimally positioned transducers  and usinThe feasibility of CWI to detect small-scale velocity changes very early has been demonstrated.The decorrelation of wave forms indicates the spatial extent of the damage, enabling the detection of distributed microcracking in early stages of the loading, while a constant diffuse damage shows almost no change in the decorrelation coefficient.On the specimen level it was possible to differentiate between diffuse and localized damage using CWI.Comparing reflective and absorbing boundary conditions revealed with absorbing boundary conditions, it was no longer easily possible to distinguish localized and diffuse damage as the lack of reflections from the boundaries significantly reduces illumination of the damage.Applications of CWI on larger scale specimen should prioritize long recording lengths to monitor and discriminate multi-scale damages.The use of multiple optimally placed transducers seems to be crucial for structural health monitoring of infrastructures.The sensitivity of Coda Wave Interferometry to different damage scenarios has been investigated numerically. Realistic numerical concrete models were created with three different grain size ranges. The response of concrete specimen subjected to uniaxial tension has been simulated by means of the discrete element method to generate a set of virtual mesostructural concrete models with evolving microcracks, which are eventually coalescing into a macrocrack. Simulations of the ultrasonic wave propagation were performed on these models for all stages during tensile loading and compared to scenarios, where a constant diffuse damage has been assumed in the mortar matrix and the grains, respectively. The main conclusions of this study are as follows:


The study results revealed desirable parameters and features of paving surfaces. People who use manual wheelchairs and declare limb loss prefer medium- and large-format concrete pavers with smooth finishing and no bevelling. People with skeletal abnormalities or peripheral neuropathy prefer concrete slabs and surfaces made of small- or medium-sized panels arranged in a regular pattern, made of smooth non-slip concrete with narrow joints. Further laboratory tests are necessary to investigate whether increased water permeability of pavements constructed on eco-friendly base layers can curb damage to the pavement surface and provide long-term durability.People with locomotion difficulties encounter many barriers in a pedestrian environment. Pavement quality has been shown to substantially affect pedestrian satisfaction in general, and its optimal design may contribute to reducing the stigma put on people with impairments. Our research involved a survey assessing perception and attitudes towards pavement quality and characteristics for pedestrian comfort. The classic correlation of the variables based on contingency tables was used to analyse data and to test whether respondents’ perceptions depended on certain profile features. The completion of the statistical inference was the use of advanced algorithms of the correspondence analysis method. The relationships between the variables were assessed optionally using the chi People with motor disabilities often experience mobility difficulties. The definition of disability proposed by the WHO  is a multidimensional term covering disability, activity limitations, and participation limitations, reflecting the interaction between the characteristics of a person’s body and the characteristics of the society in which they live . Groups However, mobility difficulties affect a much larger group of people. Health-related insufficient physical activity is a common problem among seniors ,4, but iThe problems usually result from inadequate sidewalk design or construction, poor maintenance, or even natural characteristics of the terrain. Obstructions such as uneven surfaces, litter, overgrown vegetation, kerbs without ramps , badly-sField observations indicate that some pavement damage occurs because of tree root interactions with the pavement ,15. TreeOn the other hand, the presence of trees in the city, including those growing along the pavements, has an impact on residents’ well-being ,29,30,31There seems to be a conflict between keeping trees in the city and maintaining pavement quality. Permeable pavements with an adequate base layer may be a solution as a rapid increase in impermeable paved surfaces in urban areas may result in flash floods and economic costs ,39. Howep < 0.0001) and between the pavement surfaces (p = 0.004) [In addition to dedicated solutions (tactile ground surface indicators—TGSI) for visually impaired people  or ramps= 0.004) . HoweverThe conventional approach to proper pavement design includes testing the level of stresses, strains, deflections, and deformations resulting from the quality of the subsoil ,48; mateBarriers encountered by people with mobility difficulties are still a rarely undertaken issue. The main research gap is the lack of an interdisciplinary research approach combing social inclusiveness for people with mobility difficulties, technical issues concerning rain-water resilience, and environmental issues related to trees’ root system protection. This study is the first stage of the more comprehensive research. This study is aimed at determining the optimal parameters of pavement surface in terms of pedestrian comfort and unhindered movement of people with a motor disability. Results of our previous study based on in-depth interviews and “walk-and-interviews” revealed that asphalt and concrete paving surfaces are preferred over mineral surfaces used in urban public parks by people with disabilities . TherefoWe wanted to test which features of paving surface are crucial, the size, joints, or the pattern, for the comfort of pedestrian circulation . This criterion enabled us to gather respondents who are particularly sensitive to the pavement quality. Our study involved a survey designed to assess perception and attitudes about pavement quality and parameters to ensure pedestrian comfort. To test the survey, we undertook a pilot survey among 15 respondents. The survey was voluntary and anonymous. The data were collected between 17 September 2021 and 17 October 2021. A link to the survey was distributed among 11,349 members of the Avalon Foundation  Figure  via emaiAccording to the data of the Social Insurance Institution , in December 2019, there were 2.4 million people in Poland receiving retirement and disability benefits, holding a certificate of disability or a certificate of incapacity for work ,57,58,59The sample included people living in different types of places of residence: large (32.3%), medium-sized (16.8%), or small cities (27.7%); suburbs (5.2%); and rural areas (18.1%) . Most reThe survey was based on a structured questionnaire with two main sections: (1) respondents’ profile and (2) questions concerning pavement features . First, 2 test through the SPSS software.The classic correlation of the variables according to the contingency tables was used to analyse data and test whether respondents’ perceptions depended on certain profile features. The completion of the statistical inference was the use of advanced algorithms of the correspondence analysis method. The relationships between the variables were assessed optionally using the chi2 statistic. Additionally, profiles were created on the basis of chi2 statistics, which enabled the determination of the number and strength of hidden relations in the input data set. Another complementary element that introduced advanced tools to the entire analysis was the creation of a script generating sequence charts based on Burt tables resulting from the correspondence analysis.Advanced algorithms in the manuscript were at the root of correspondence analysis. Correspondence analysis was based on factor analysis, the only difference being that it operated on qualitative variables. The degree of advancement of this analysis resulted from the inference method being similar to the factor analysis in which we rotated the created system to maximise the variance explained by the successive coordinates of this space. Moreover, it was based on the classical analysis of the multidimensional table in which the strength of the relationship between the variables was described using the chiThe assumed hypotheses were as follows:Hypothesis 1 (H1).The inadequate quality of the pavement is a common barrier for pedestrian circulation for people with a motor disability.Hypothesis 2 (H2).Concrete paving is the most preferred solution for the comfort of pedestrian circulation, according to people with motor disabilities.The study was focused on a correlation between equipment/aid used for mobility and preferred pavement parameters by comparing data in cross-tables made in SPSS version 26.0  and correspondence tables, diagrams, and graphs using Statistica software.The study confirmed hypothesis 1 (H1) that “inadequate quality of pavements is a common barrier in pedestrian circulation for people with a motor disability” . OverallMore information is provided by our sequence chart that shows the numbers according to the type of disability and the way of movement in a matrix. The results are shown in The study confirmed hypothesis 2 (H2) that “concrete pavement is preferred in terms of comfortable pedestrian circulation by people with a motor disability”. In addition, the results indicated that large-format concrete slabs were the most desirable .2 statistic <0.001 suggests a relationship between preferences regarding the type of pavement, type of disability, and the manner of moving around. Dimension 1 determines the hidden relationship between the variables and divides the strength of preferences for a given surface vs. the type of disability, while dimension 2 discriminates the type of pavement vs. the type of mobility aid, but additionally introduces additional discriminatory power in the form of eliminating respondents who showed indecision when indicating their preferences regarding the type of pavement. The first two dimensions with the highest inertia were used in the analysis. The first dimension divides a given feature according to acceptance level, separating the respondents’ feelings about the moving comfort on a given pavement type. It also demonstrates the respondents’ opinions by placing their strong preferences on the right. In the most extensive grouping of effects, less decisive responses dominate. The second dimension separates the response space regarding the type of equipment/aid used. For example, the green colour marks the respondents using walking frames who prefer the large-format concrete slabs (L-S CS), small jointless concrete pavers (N-JC), and asphalt (B). On the other hand, people using crutches prefer small format slabs with joints (JC), small jointless concrete pavers (N-JC), and large concrete (L-S CS) surfaces but do not like asphalt (B) or earthen pathways.The multidimensional analysis of the correspondence based on Burt’s tables allowed for the drawing of additional conclusions . The chiInterestingly, people who use manual and electric-powered wheelchairs have an undefined profile, which means they have a high level of acceptance for many types of surfaces. Therefore, particular focus should be placed on surfaces common to all groups (assistive equipment used). In this case, from the point of view of ease of movement, optimal surfaces are jointless large-format slabs (L-S CS) and small format jointless concrete pavers (N-JC) .Important findings were obtained from a series of answers concerning the comfort of pedestrian circulation on a given type of pavement. The results are presented in a sequence chart . AnalysiThe respondents declared that large concrete paving slabs and small jointless concrete slabs were convenient. This result was obtained, regardless of the disability or equipment used to move around. It should be added that this conclusion was evident despite the large proportion of people representing one type of disability (damage to the nervous system). From the observations above, it follows that large concrete paving slabs are the most preferred pavement surfacing type. The respondents indicated several pavement characteristics and parameters that significantly impact the comfort of moving  . The resPavement texture: smooth non-slip concrete.Concrete slabs with a narrow joint.Concrete slabs without openings.Large paving slabs.A slab with simple patterns, two sizes, no bevelling.A medium-sized concrete slab with smooth finishing and a regular pattern.The respondents’ opinions on specific pavement parameters are crucial for hypothesis 2 “concrete pavement is preferred in terms of comfortable pedestrian circulation by people with a motor disability”. First, an analysis of the contingency table was performed, considering the effect of the equipment/aid used for pedestrian circulation . The per2 test <0.001 suggests a significant relationship between the equipment/aid used and the preferred features of the concrete pavement. The grouping results show that the first dimension discriminated/distinguished concrete pavement characteristics, indicating the lack or presence of impact of a given feature on the comfort of movement. The second dimension turned out to be more important and divided the respondents by the assistive devices they used. As a result, we found that people using manual wheelchairs and declaring limb loss prefer medium-size and large concrete slabs with smooth finishing, without bevelling. On the other hand, people using walking frames and electric-powered wheelchairs prefer concrete slabs and other surfaces made of small- or medium-sized slabs with a regular pattern made of smooth non-slip concrete with narrow joints (Only the two most important dimensions (with the highest inertia of the variables) were used in the further analysis. The chiw joints . The corw joints .Social inclusion in universal design refers to “a process that enables and empowers a diverse population by improving human performance, health and wellness, and social participation” . It makeThe study results revealed various barriers city residents with motor disabilities encountered in terms of movement comfort and pavement quality . Given tSome barriers, including uneven pavement surface , are relHowever, our research indicates contradictory expectations towards pavements. Asphalt surface, indicated by as a comfortable for movement by the respondents , due to We carried out our study during the fourth wave of the COVID-19 pandemic, and for health and safety purposes, the survey was conducted on a sample of internet users. Therefore, the model may not represent the target population, but it certainly shows the attitudes of specific groups of people with motor disabilities. As the municipalities or the Statistical Office provide no data concerning the number of manual/electric wheelchair users or people using crutches or “walking frames”, we cooperated with the largest foundation  for people with all types of disabilities in Poland. The mailing report from the Avalon Foundation states that our survey was sent to over 11,000 people on their mailing list with a response rate of 2.36% . Therefo2 test) provides us with information about the structure of relationships between the columns and rows of the multi-way table of the data set. It can also prioritise the strength of hidden effects in the relationship between the rows and columns of multi-way tables. It is similar to factor analysis but provides information on categorical variables. Hill developed detailed assumptions in 1974 [Correspondence analysis was implemented to search for hidden relationships in qualitative traits. Of course, correspondence analysis only suggests some relationships between the variables within the examined set, which are difficult to detect with other methods. It is a tool that allows for the finding of specific relationships between the analysed variables. In the classical multidimensional analysis, information is obtained only regarding the strength of the relationship between the qualitative variables. Correspondence analysis is based on these assumptions, but introducing a metric . Moreover, the necessity of using heavy equipment to install asphalt makes its use sometimes impossible, especially in places with already existing trees. Therefore, we resigned from testing this solution in detail. Concrete being the “stone of the 20th century” and the most popular material used for pedestrian surfaces (for its price and availability) was chosen as the dominant subject of the study. However, it may be in many cases used interchangeably with stone surfaces. During the study, we obtained data that allowed for the description of the desirable parameters and features of comfortable paving surfaces indicated by people with certain types of mobility difficulties.There is a continued need to address the barriers faced by people with motor disabilities. The response to discriminatory pavement deficiencies needs to be improved in terms of the accessibility of various public spaces and services offered by cities to mobility-impaired people.Further research should therefore focus on field/laboratory tests of pavement characteristics defined in our study, improved in terms of water permeability features combined with the appropriate pavement base structure. Furthermore, additional tests are needed to analyse the vibration level and water permeability. This study is significant in providing the evidence that there are certain pavement surface features that impact on comfort of walking. The findings may be potentially applicable to other cities, as urbanites worldwide continue to find ways to convince residents to pedestrian circulation and resign from cars.


In this study, the transformation products formed were identified, and the mineralization degree of compound was determined. The efficiency of metronidazole removal depending on the type of catalyst was in the range of 50–95%. The highest MET conversion (95%) combined with a high degree of mineralization (70.3%) was obtained by using a mixture of 12.5 g TiO2–P25 + PbS  and running the process for 60 min at an irradiance of 1000 W m−2. Four MET degradation products were identified by untargeted analysis, formed by the rearrangement of the metronidazole and the C-C bond breaking.Metronidazole (MET) is a commonly detected contaminant in the environment. The compound is classified as poorly biodegradable and highly soluble in water. Heterogeneous photocatalysis is the most promoted water purification method due to the possibility of using sunlight and small amounts of a catalyst needed for the process. The aim of this study was to select conditions for photocatalytic removal of metronidazole from aquatic samples. The effect of catalyst type, mass, and irradiance intensity on the efficiency of metronidazole removal was determined. For this purpose, TiO DP3 adiation . DP3 wasadiation . DP4 wasadiation . DP1 is adiation ,70.−1, and the MET conversion was 95% in only 30 min. The Degussa P25 + WO3, ZnO + PbS, and Degussa P25 + ZrO2 mixtures also showed good photocatalytic performance, for which the MET removal efficiency in 60 min was as high as 94%. The highest photocatalysis efficiency was obtained at an irradiance of 1000 W m−2, where 95% of MET was removed in 30 min. The lowest MET removal efficiency  was obtained using an irradiance of 250 W m−2, corresponding to the average irradiance in Poland over a year. It was concluded that full conversion of MET using solar would require prolonging the photocatalysis time or using additional light sources.In this study, parameters were selected for the photocatalytic removal of MET in aqueous samples. The best catalyst proved to be a Degussa P25 + PbS mixture, for which the reaction rate constant was 0.0889 minTOC changes was in the range of 36.0% (ZnO + WO3)–70.30% (Degussa P25 + PbS). Due to the discrepancy between the MET conversion of 95% and the MD of 70.3% in the model samples, four metronidazole degradation products were identified, and their structures were confirmed from data in the literature. The DPs were formed by rearrangement of the metronidazole ring and the C-C bond breaking in reaction with hydroxyl radicals.The degree of sample mineralization determined by −2, allows efficient removal of METs from aqueous solutions. It should be emphasized that the effectiveness of the Degussa P25 + PbS mixture was tested in an aquatic environment, in a neutral reaction, in which PbS appears as an insoluble substance, whereby the potential environmental impact of PbS is substantially reduced. The use of a small amount of photocatalyst is attractive considering economic issues; however, the inability to use only sunlight as the irradiation source may significantly limit its application potential.The photocatalytic process procedure developed for the first time, using a Degussa P25 + PbS mixture with an irradiance of 1000 W m


This work addresses how vibration stirring, steel-fiber volume ratio, and matrix strength affect the mechanical properties of steel-fiber-reinforced concrete. The goal of the work is to improve the homogeneity of steel-fiber-reinforced concrete, which is done by comparing the mechanical properties of steel-fiber-reinforced concrete fabricated by ordinary stirring with that fabricated by vibration stirring. The results show that the mechanical properties of steel-fiber-reinforced concrete produced by vibration mixing are better than those produced by ordinary mixing. The general trend is that the mechanical properties of steel-fiber concrete have a linear relationship with the matrix strength and the volume ratio of steel fiber. The best mechanical properties are obtained for a steel-fiber volume ratio of less than 1%. We have also established calculation models for the mechanical performance index of vibration, mixing steel-fiber concrete based on the test results. Microscopic studies show that vibration stirring optimizes the microstructure of the transition zone between the concrete interface and the slurry, and improves the homogeneity of the steel-fiber-reinforced concrete, and enhances the adhesion between the mixture components. With the continuous improvements in engineering construction levels, concrete has gradually become the most widely used engineering material. Concrete is made of cementitious materials, aggregates and water in an appropriate proportion and is mixed to make a mixture with a certain degree of plasticity. It has a high compressive performance, but its tensile performance is only 1/10–1/20 of its compressive strength. Therefore, improving the ratio of concrete tensile and compressive strength is an important aspect of concrete modification. The incorporation of steel fiber can effectively improve the tensile properties of concrete, enhance cracking control, and improve the overall performance of structural members. Steel-fiber-reinforced concrete is an extremely inhomogeneous composite material prepared and conserved by steel fiber, cement, sand and stone, etc. ,4 The peThe above research shows that adding steel fiber to concrete can effectively improve the mechanical properties of concrete, but there are also obvious limitations: steel fiber is easy to agglomerate during the mixing process, and it is difficult to evenly distribute it in the mixture; the bonding strength between steel fiber and concrete is not enough, which affects the tensile effect. The random distribution of steel fibers in reinforced concrete can effectively hinder the expansion of micro-cracks and the formation of macro-cracks in the concrete, and transfer stress across the crack surface after cracking, significantly improving the brittle behavior of concrete ,17,18,193, and the loose bulk density is 1514.5 kg/m3. The sieve classification results of the sand are shown in the following Tianjin Hengfeng  end-hook-type steel fiber was used for these experiments; the fibers were 30 mm long with 0.55 mm equivalent diameter, for a length-to-diameter ratio of 64. The ensile strength was 1000 MPa. As shown in (1)Determine the water-binder ratio W/BThe tests were conducted following the relevant standards and specifications ,30. The In the formula: (2)Determine unit water consumption (3)Determine the unit amount of cement The water-binder ratio is constant. The main factor that affects the workability of the mixture is the water consumption per unit volume. According to the workability requirements and the water reducing efficiency of the water reducer.The amount of fly ash in this test is 10% of the mass of the cementitious material. According to the unit water consumption and the water-binder ratio, (4)Determine the sand rate Sand rate affects the strength and homogeneity of steel fiber concrete. Taking into account these two aspects, according to relevant specifications and experience, the sand rate is determined by the water-binder ratio and the maximum particle size of the aggregate .According to the above calculation process, the coordination ratio of this test is determined as shown in (1)Vibration mixerThe experiments used a DT60 ZBW  double-horizontal-shaft vibration mixer to fabricate the test pieces . This in(2)Press machinesAs shown in (3)Scanning electron microscopeUsing SBC-12 ion sputtering instrument  and KYKY-EM6200 scanning electron microscope , as shown in By comparing the performance of reinforced concrete with different matrix strengths and different mix ratios under ordinary mixing and vibration mixing, it can be seen that vibration mixing has a significant impact on the performance and failure mode of reinforced concrete. It has different influence rules on the compressive strength, tensile strength, elastic modulus and flexural strength of reinforced concrete.It can be seen from It can be seen from It can be seen from the above test results that when the amount of steel fiber is small, the influence of steel fiber on the compressive strength of concrete is less than the influence of vibration mixing on the compressive strength of concrete. This is because the steel fiber mainly inhibits the expansion of concrete cracks through the viscous stress between the two sides of the concrete cracks and improves the overall performance of the concrete. At this time, the effect of vibration mixing on the workability of concrete is better than the effect of the steel fiber volume rate on compressive strength.The tests show that the factors affecting the compressive strength of steel-fiber concrete cubes include vibration stirring, matrix strength, and steel-fiber volume ratio. We use the following simple model to calculate the relationship between vibration mixing and the compressive strength of steel-fiber-reinforced concrete cubes:The data fitting analysis gives the cube compressive strength coefficients for vibration stirring, matrix strength, and a steel-fiber volume ratio of 1.06, −0.1, and 0.11, respectively. The cube compressive strength for vibration stirring is calculated as follows:It can be seen from the test results that when the volume ratio of steel fiber is higher than 1%, the higher the strength of the matrix, the lower the increase in elastic modulus by vibration stirring. The main reason is that when the strength of the matrix increases, the water-binder ratio of concrete decreases and the amount of cementing material is large, and the fine cemented particles cannot be dispersed by vibrating stirring under the condition of vibration pressure of 0.55 MPa.Based on the calculation of elastic modulus of ordinary-stirred steel-fiber-reinforced concrete, the calculation of the elastic modulus of vibration-stirred steel-fiber-reinforced concrete isAccording to the data, the elastic-modulus coefficient is 1.03 and 0.16 for vibration stirring and the steel-fiber volume ratio, respectively. The elastic modulus for vibration-stirred steel-fiber concrete is thusThe error range between experimental and calculated results is within 10%, the mean value of the ratio is 1.0416, and the mean square error is 0.0648.It can be seen from It can be seen from Because the surface of the aggregate will adhere to dust, a water film will form to isolate the cement particles from the aggregate after encountering water, which affects the cementing material and the bond between the steel fiber and the aggregate, thereby affecting the overall strength of the concrete. The high-frequency vibration of vibratory stirring makes the dust attached to the surface of the aggregate peel off and the aggregate is wetted, which accelerates the hydration reaction of cement particles, reduces the generation of steel fiber clusters, and improves the overall strength of the concrete.The experiments show that the splitting tensile strength depends only slightly on the matrix strength. Therefore, we consider only the other two factors in the following calculation of the splitting tensile strength of vibration-stirred steel-fiber-reinforced concrete:Based on the data analysis, the splitting tensile strength coefficients are 1.09 and 0.33 for vibration stirring and steel-fiber volume ratio, respectively. In other words, the splitting tensile strength of vibration-stirred steel-fiber-reinforced concrete may be calculated by usingThe error range between experimental and calculated split tensile strength is less than 10%, the average value of the ratio is 0.9892, and the mean square error is 0.0698.Experiments show that the flexural strength of steel-fiber-reinforced concrete is affected by various factors, including vibration mixing, matrix strength, and the steel-fiber volume ratio. Therefore, the flexural strength of the steel-fiber-reinforced concrete is calculated asFitting the data gives the flexural-strength coefficients for vibration stirring, matrix strength, and a steel-fiber volume ratio of 1.10, −0.1, and 0.45, respectively. The flexural strength of vibration-stirred steel-fiber-reinforced concrete is thusThe error range between the split tensile strength test and the calculated value is less than 10%, the average value of the ratio is 1.003, and the mean square error is 0.0596.We performed a regression analysis on the data of 1.When the concrete grade is the same, the concrete performance after vibration mixing is higher than that of ordinary mixing. Among them, the improvement efficiency of compressive strength and elastic modulus is more obvious when the amount of steel fiber is low, and the efficiency of splitting tensile strength and flexural strength is more obvious when the amount of steel fiber is high. From the improvement effect of concrete performance and the influence coefficient fitted by the data, it can be seen that the influence of vibration mixing on concrete performance from high to low is: flexural strength > splitting tensile strength > compressive strength > elastic modulus.2.With different matrix strengths, when the volume ratio of steel fiber is higher than 1%, the higher the matrix strength, the lower the increase in elastic modulus and flexural strength of vibration stirring. The main reason is that when the strength of the matrix increases, the water-binder ratio of the concrete decreases and the amount of cementitious material is large, and the fine cementitious particles cannot be dispersed by vibrating stirring.3.The addition of steel fiber and vibration mixing can improve the failure morphology of concrete specimens. The larger the volume ratio of steel fiber, the higher the strength of the matrix, the fewer cracks and the less the amount of spalling, and the better the integrity of the specimen.4.From the study of the microscopic morphology of the vibration mixing steel fiber concrete, it can be seen that the vibration mixing improves the performance of the transition zone of the concrete interface and the slurry, and increases the structural bonding force. Vibration mixing makes the mixtures have a better compactness and a better performance. At the same time, the steel fibers are evenly distributed among the mixtures to avoid agglomeration, which is beneficial to improve the performance of steel fiber concrete.Based on the vibration mixing technology, this paper carried out experimental research on the mechanical properties of steel fiber concrete, and analyzed the microscopic appearance of steel fiber concrete to explore the mechanism of the effect of vibration mixing on the performance of steel fiber. Combining vibration mixing technology, steel fiber volume ratio and matrix strength to study its influence on the performance of steel fiber concrete, it is found that vibration mixing technology can effectively improve the homogeneity and integrity of steel fiber concrete. The main conclusions of this paper are as follows:


The materials chosen to replace the river sand are manufactured sand (M-sand), sea sand, copper slag, quarry dust, and limestone sand as 25%, 50%, 75%, and 100%, respectively by weight. GPF50 and CC50 were kept as control mixes for GPC and CC, respectively. The test results of respective concretes are compared with the control mix results. From compressive strength results, M-sand as a fine aggregate had an increase in strength in every replacement level of GPC and CC. Additionally, copper slag is identified with a significant strength reduction in GPC and CC after 25% replacement. Copper slag, quarry dust, and limestone sand in GPC and CC resulted in considerable loss of strength in all replacement levels except for 25% replacement. The cost of GPC and CC is mixed with the selected fine aggregate replacement materials which arrived. Durability and cost analyses are performed for the advisable mixes and control mixes to have a comparison. Durability tests, namely, water absorption and acid tests and water permeability and thermal tests are conducted and discussed. Durability results also indicate a positive signal to mixes with M-sand. The advisable replacement of river sand with each alternative is discussed.The aim of this research was to find the best alternative for river sand in concrete. In both geopolymer concrete (GPC) and cement concrete (CC), the fine aggregates are replaced with various sustainable mineral ashes, and mechanical and durability tests are conducted. Specimens for tests were made of M About 60 to 80 percent of the concrete is occupied by fine aggregate and coarse aggregate ,2,3. Riv studies . The cem studies .Conservation of river sand is a major issue now. Governments are protecting river sand from use by construction companies who cannot use it as before. To minimize the usage of river sand, many researchers have attempted to use GPC and CC with various soil types as fine aggregates . Studies40 grade of GPC and CC are taken to replace the fine aggregate. Manufactured sand, sea sand, limestone sand, copper slag, and quarry dust are considered as river sand replacement materials in this research. The compressive strength test on fine aggregate-replaced specimens was conducted for 7 and 28 days. Durability tests, namely, the water absorption and acid test, and the water permeability and thermal test were conducted and recorded. Cost analyses for respective mixes give an additional advantage to this research.However, this research concentrates on finding the most suitable substitute from the waste and natural materials for river sand in concrete. Both cement and geopolymer binders are selected to bind the aggregates. The M2O and SiO2). Ordinary Portland cement of grade 53  was used to get a cement binder. Quarry dust, M-sand, sea sand, limestone sand, copper slag, and river sand  were used as fine aggregate. M-sand and quarry dust were obtained from a nearby crusher. The manufacturing of M-sand involves crushing, screening, and washing. Quarry dust is the leftover material from the extraction and processing of rocks to make M-sand [Six types of fine aggregates were used in this research to study the influence of each material on the properties of concrete. GGBS and fly ash were used as powders in GPC. To obtain GPC, alkaline liquids, namely, sodium silicate and sodium hydroxide were used. The 10M NaOH was obtained by diluting pellets  in water. Glass silicate was obtained with a water content of 55% and 45% solid content . Cement concrete specimens were dipped in water for curing until the day of testing. The tests on fresh and hardened concrete were conducted as per Indian codal provisions.Slump cone was conducted to find the workability of concrete. Both the geopolymer and cement fresh concretes with various types of fine aggregates were allowed to conduct the slump cone test. The test was conducted as per IS 1199-1959 .Cube and cylinder specimens of the respective mixes recorded in To find the percentage of water absorbed, 150 × 150 × 150 mm cube specimens of the mixes recorded in 2SO4)  solution with a pH value of 0.2 for 25 days, as per the literature [For the acid test , after dterature . The speterature .2 of air pressure was applied for the constant flow of water for 100 h. The water permeability instrument setup is shown in IS 3085:1965  was refeThe compressive strength of geopolymer concrete and cement concrete mixes subjected to a temperature range of 200 °C and 400 °C for 24 h was observed and recorded. The cube specimens with a size of 150 × 150 × 150 mm were cast for the mentioned mixes after 28 days and kept in a heat oven at a temperature of 200 °C and 400 °C for 24 h. Beyond that, the amount of strength loss was determined by conducting compression tests on the specimens. The durability results are represented graphically in clause 5.2.Even when a material performs well in all aspects, its cost must be reasonable to society to use it. Considering that, the costs of each mix were based on the South Indian market price. This would be most useful for persons who want to choose the materials based on the cost too. Clause 4.3 clearly discusses the costs incurred for respective mixes.It can be observed that an increase in quarry dust, sea sand and limestone sand in GPC and CC mixes obtains a decrease in workability when compared to the control mix. To maintain workability levels similar to the control mix for respective mixes, extra water is needed. In the same way, water can be saved from highly workable concrete mixes with copper slag to maintain constant workability with the control mix. This study did not add or remove water from the designed proportion, so as to study the actual behavior of each fresh concrete mix.The compression and split tension strength results of mixes shown in Considering the GPC test results, keeping the control specimen as a benchmark, M-sand at all replacement levels, copper slag at 50% replacement, and quarry dust at 25% obtained an increase in strength. Beyond 50% of copper slag and 25% of quarry dust, a decrease in strength was found at GPC. Limestone sand as the fine aggregate of GPC did not meet the strength levels of control specimens in all replacement levels. Considering the compressive strength, M-sand in the GPC mix got an increase in value when compared to the other sand types . SignifiConsidering the CC test results, comparing to the control mix, M-sand at 75% replacement, copper slag up to 25% replacement, sea sand up to 50% replacement, quarry dust at 25%, and limestone sand at 25% got an increase in strength. Beyond 75% of M-sand, 25% of copper slag, 50% of sea sand, and 25% of quarry dust, a decrease in strength was found in CC. Limestone sand as the fine aggregate of CC did not meet the strength of control specimens only at 25%, and in all replacement levels, it had a decrease in strength. The strength of mixes CCFM3, CCFC1, CCFS2, CCFQ1, and CCFL1 were considered to be optimized while using M-sand, copper slag, sea sand, quarry dust, and limestone sand. These mixes achieved an increase in strength of about 8.07%, 6.01%, 3.04%, 0.90%, and 1.40% when compared to CC, respectively.Split tensile strength results for the GPC and CC mixes were found to get corresponding variations as found in compressive strength. Sea sand, copper slag, quarry dust, and limestone sand were unable to enhance strength more than the control mix in both GPC and CC in full replacement. The mixes that achieved higher compression values with different fine aggregates were selected to conduct durability tests. GPF, GPFM4, GPFC2, GPFS1, GPFQ1, and GPFL1 are the mixes considered in the side of GPC. Mixes CC, CCFM3, CCFC1, CCFS2, CCFQ1, and CCFL1 were considered in the CC side. The other mixes that did not get reasonable strength when compared with the control mixes were not subjected to durability tests.The strength properties of the mixes tested for geopolymer concrete and cement concrete are reflected in the durability test results. The results shown in However, in loose aggregate concrete specimens, the absorption was found to be more. Both in geopolymer and cement concrete, M-sand and copper slag contained specimens which absorbed less water when compared to the control specimens. This clearly shows that M-sand and copper slag has naturally low water-absorbing capacities. Sea sand, quarry dust, and limestone sand absorbed a high percentage of water due to their absorption capacity. The surfaces of the specimens after taking out the acid solution are rough and do not resemble the control specimens. The specimens were weighed and tested under compression. The loss of strength and weight are noted in In both GPC and CC, M-sand and copper slag-based specimens gave good results. Nearly 0.20% of weight loss of GPC and 0.23% of weight loss of CC was reduced by using M-sand, respectively. About 0.16% of weight loss was found in GPC and 0.22% of weight loss of CC was reduced by using copper slag, respectively. The weight loss using copper slag was too low, and may have happened due to some reaction between the copper slag and sulfate solution . In GPC,Water permeability under pressure was calculated and recorded in The thermal test results are shown in 40 grade concrete is nearly 23.22% higher than CC in cost. Although the cost is higher, ecofriendly concrete is GPC. Therefore, this cost variation will not have a huge impact on GPC mixes. Considering the rates aggregate-wise, M-sand was better than river sand in strength, and durability also had an effect with regard to cost. M-sand-based GPC and CC saved costs of about 8.30% and 14.86%, respectively. Mixes with M-sand obtained better results in strength and durability. Additionally, using it can result in a more low-cost concrete than river-sand-based concrete. The other types of fine aggregates also considerably reduce the cost of GPC and CC concretes.The cost, strength, and durability of concrete are the three most significant aspects in construction. Civil engineering is always interested in any breakthrough that has a positive impact on these aspects. The variations in cost for the mixes discussed above are given in The following conclusions can be taken from the outcomes reported in this study. Replacement of river sand in geopolymer concrete and cement concrete is possible using M-sand, copper slag, and quarry dust. The workability and strength of GPC- and CC-based concrete with M-sand and copper slag as fine aggregates were found to be good. Compared to copper slag, sea sand, quarry dust, limestone powder, and river sand, M-sand was found to be good in the workability and strength aspects. Up to 100% of the river sand could be replaced in GPC and up to 75% of river sand could be replaced in CC. Copper slag occupied a position next to M-sand. Nearly 50% of the copper slag can be replaced for GPC and 25% for CC. Quarry dust for both types of concrete is eligible only up to 25%, and the remaining goes for river sand. Sea sand in GPC improves the strength, but in durability studies, it failed to footprint, so it cannot be referred to as a good replacement material for river sand. Limestone sand was found to get a continuous drop in strength levels after 25%. Only the use of a small percentage of limestone sand below 25% is advised.The depth of water absorption was reduced in GPC due to the gel-foam packing between the pores. Other than this, the fine aggregate materials, which are good in water absorption like sea sand, quarry dust, and limestone sand, were found to increase in water absorption value. This absorption of water may sometimes increase the mass of concrete and create internal damages in RCC structures. M-sand and copper slag-based GPC and CC were found to have low water absorption values.Sulfuric acid attack in CC is aggressive. This type of acid attack may reduce the strength of concrete and also reduce its mass. Results clearly showed the domination of GPC in resisting sulfuric acid attack when compared to CC. A rough surface was found on the 28th day of CC specimens. Specimens of GPC did not deteriorate over its surface. The surface was found to be smooth and good after 28 days. The silica content in the GPC fills the pores and effectively resists the acid attack. The only substantial changes occurred in the strength of GPC specimens, and CC specimens exhibited larger changes. Similar to water permeability, river sand, M-sand, and copper slag-based GPC were found to be resistant towards sulfuric acid attack. The surface of the sea sand-based specimens was found to be rough when compared to other specimens, both in GPC and CC. Considerable losses in strength and weight were also found for limestone sand. For both the GPC and CC specimens, strength loss occurred within 200 °C to 400 °C. At 400 °C, the CC specimens were found to degrade slightly over their surface, and such an effect was not found in GPC specimens. The increase in temperature may have affected the chemical bonding of both GPC and CC specimens. The exact temperature at which the reaction occurs should be discovered in future. M-sand-based GPC and CC specimens performed well at both temperatures. Only a small percentage of strength loss was found.M-sand as fine aggregate was found to be good in the aspects of strength and durability as well as cost-wise when compared to river sand. About 8.30% and 14.86% of the cost could be reduced in both GPC and CC specimens by using M-sand as a fine aggregate, which also gave an increase in strength. Even though copper slag, quarry dust, and sea sand had a significant effect on strength improvement, they did not shine in the durability aspects. Thus, M-sand was found to be a good alternative for river sand both in the GPC and CC structures.


Today, it’s getting harder to find natural resources for concrete production. Utilization of the waste materials not just helps in getting them used in concrete, cement, and other construction materials, but also has various secondary advantages, for example, saving in energy, decrease in landfill cost, and protecting climate from pollution. Considering this in the development of modern structural design, utilizing waste materials instead of natural aggregate is a good option to make concrete that is sustainable and eco-friendly. The present research aims to find the impact of adding glass fiber into sustainable concrete made with silica fume, as a partial replacement of cement, and coconut shell added with different ratios as a replacement of coarse aggregate, on concrete mechanical and durability aspects. Various blends were made, with coconut shell as a substitution of coarse aggregates with different ratios. Portland cement was substituted with silica fume at 5%, 10%, 15%, and 20% by cement weight in all concrete blends. The volume ratios of glass fibers utilized in this study were 0.5%, 1.0%, 1.5% and 2.0%. Adding glass fibers increases concrete density to some extent and then marginally reduces the density of coconut shell concrete. When the percentage of glass fibers increases, the compressive, flexural and split tensile strength of coconut shell concrete also increases. From the lab results and SEM images of the present research display that glass fibers might be utilized in coconut shell concrete to enhance its mechanical and durability attributes, to accomplish sustainable concrete with acceptable strength with ease. Researchers in writing2 announced that the present phase of the construction industry is not sustainable. Sustainable construction could be accomplished in the industry by substituting normal crushed stone in concrete with strong recycled products. Crushed stone aggregates and fine are around 65–85% of the volume of concrete5. However, the utilization of conventional coarse aggregates subverts sustainability, as it prompts additional environmental issues6. As per the India Farmer's Welfare and Horticulture Ministry, in 2016–2017 over and above 2390 Billion coconuts have been formed in India7 this will increment the farming waste accumulation. Thus, the successful usage of agricultural wastes, as a substitute for normal aggregates, contributes to the preservation of depleting resources which is non-renewable, decreases utilization of energy, and also decreases the expenses of construction materials. Authors has utilized a few scrap matters in concrete, with recycled aggregate, fly ash, silica fume waste elastic tire, and GGBFS and waste and glass plastics9. Moreover, tobacco wastes, coconut shell (CS), rice husk ash, palm shell, pistachio shell, oil palm shell (OPS), utilized to deliver lightweight aggregate concrete. Therefore, the protection of the environment could be accomplished by the best utilization of this type of agricultural wastes2.Sustainability might be defined as the capacity to retain depleting nonrenewable resources and renewable resources use indefinitely. Sustainability is one of the highest studied yet least comprehended words on the planet. For most of the countries, associations, and individuals who think about its significance, sustainability implies the Earth preservation and critical matters connected to development, for example, stable economic growth, productive usage of resources, poverty elimination, and consistent social advance. Sustainable construction expects to meet present prerequisites for a working situation, housing, and infrastructure without trading off people's capacity in the coming years to address their issues10. Similarly, the replacing of normal coarse aggregates with coconut shells has paved the way for structural lightweight concrete12.The durability aspects of Coconut Shell concrete, for example, absorption, rapid chloride penetrability, color changes, the volume of porous voids, residual strength, and resistance at raised temperatures, are comparable to lightweight concretes14. Gunasekaran et al.15 demonstrated that when subjected to torsion coconut shell concrete beams behaved similarly to normal concrete. The fracture toughness and mechanical attributes of coconut Shell concrete are practically identical to lightweight concrete8.Lightweight aggregate concrete shows particular points of interest on different kinds of concrete, for example, lighter formwork, less seismic forces, lower dead weight, increased resistance to fire, smaller size foundation, better sound insulation, thermal insulation, and increased resistance to fire. Lightweight concrete for a structure might be delivered by substituting normal crushed stone with specific aggregates which are lightweight, for example, GGBFS, peach shell, pumice extended earth, clinker, and OPS19. Glass fibers have more resistance to temperature, corrosion resistance, non-flammability, and good strength in tension, but also great sound, heat, and electric padding. Glass fibers could be used in concrete for different purposes, for example, forestalling the coalescence of cracks, crack control, and changing the material behavior by cracks bridging21. Adding glass fibers to RAC was seen to enhance the tensile strength by 12–19%, and the energy absorption capacity and deformation capacity are also enhanced22. Silica fume is a byproduct of manufacturing ferrosilicon or silicon metal composites. Perhaps the most significant use for silica fume is in concrete. Due to its compound and actual attributes, it is an exceptionally passive pozzolana. Concrete that contains silica fume may be durable and could have good strength. Silica fume is acquirable from concrete admixtures providers and, when needed, it is just added into concrete. Silica fume concrete needs special consideration concerning the concrete contractual work23. According to a survey conducted in 2019 by Pakistan agricultural research council, the cultivation of coconut in Pakistan is 9917 tons annually, which is a huge number. When people will consume this much coconut it is obvious that coconut shell will cause land pollution when it is discarded in landfills. Now utilizing this coconut shell in concrete as a coarse aggregate is a perfect solution to reduce land pollution and also makes concrete eco-friendly.Adding fibrous material enhances concrete structural integrity. A recent study displays that the stresses like tensile and shear that emerge at a various cross-section of lightweight concrete might be reduced by strengthening concrete with glass fiber, natural fibers, and nylonIn the present study, various mixes were prepared in which natural coarse aggregates were replaced with coconut shell (CS) aggregates in different ratios along with silica fume and glass fibers. Crushed stone coarse aggregate was replaced with coconut shell (CS) aggregate at 15%, 30%, 45%, and 60%. Cement was partially substituted with silica fume at 5%, 10%, 15%, and 20% rates. Glass fiber was utilized at 0. 5%, 1.0%, 1.5% and 2.0% of cement weight. The goal of the present research is to explore the method of making concrete that is both an economically viable option with acceptable strength and environmentally friendly. Mechanical performance like compressive and splitting tensile strength and durability performance like density, water absorption, acid resistance tests, UPV tests, and scanning electron microscope (SEM) tests were performed, to assess concrete sustainable performance.24. The chemical and physical properties of ordinary Portland cement are displayed in Table In the present research, OPC cement was used, which is type I (42.5) general-purpose cement as per ASTM C 150Glass fibers of 18 mm were utilized for the current study for all Mixes. Its physical properties are given in Table 3 and it was utilized in all the blends. Its properties are provided in Table Natural river sand which was passed through sieve no 4.75 mm was used for the study. The sand was washed with water before it was used in concrete to make sure it had no silt content. Sand density was 1586 kg/m3 and was utilized as a coarse aggregate. The bulk density of crushed stone coarse aggregate was 1720 kg/m3, which was used with the adding of Coconut nutshell aggregate in the second mix. The difference between the density of crushed stone coarse aggregate and Coconut nutshell aggregate was 1066 kg/m3, which considerably decreases the structural member's self-weight. Physical properties of coconut shell aggregate and conventional coarse aggregate are displayed in Table Coconut shell aggregate had a unit weight of 654 kg/mSilica fume was procured from Pak re-rolling mills. Its physical properties can be seen in Table 25, and with ASTM C494 as Type A and Type F26, liable upon measurements utilized. In Table In the present research, Conplast SP 430 superplasticizer was used. It is included commonly in the scope of 0.6% to 1.3% by cement weight. The utilization of a superplasticizer makes pumpable concrete and concrete which is more workable. In the current investigation, a 0.8% superplasticizer was utilized to control test samples. Conplast SP430 meets with BS 5075, BS: EN 934-2For the control sample, we went for M20 grade concrete in which there were no CS aggregates, glass fibers, and silica fume. The complete mix design can be seen in Table 27 for cylindrical specimens having standard dimensions as 150 mm diameter and 300 mm length.Compressive strength is the measure of the greatest compressive loading concrete can withstand. The compressive strength test is completed under the standard procedure of ASTM as ASTM C39/C39M8. The positive response of compressive strength is because of the pozzolanic reaction of SiO2 in silica fume with CH of cement producing additional cementitious compounds. It has been also reported that compressive strength considerably improved with silica fume28. The extra binder formed by the silica fume reaction with existing lime Ca (OH2) permits silica fume concrete to continue to increase strength over time. However, at a higher dosage of silica fume (beyond 15% by weight of cement) strength reduce due dilution effect which leads to alkali-silica reaction due to a higher quantity of unreactive silica available is because of the silica fume high quantity. Furthermore, the positive effect on compressive strength is due to the confinement of the fiber reinforcement on the concrete sample. Compression produces an expansion laterally, and with it, tension and shear. The tension and shear are resisted by the fibers. Therefore, compression is increased. When the percentage of fibers is more this confinement can decrease concrete sample transversal deformation and enhance its compressive strength.Figure A relative analysis was carried out in which the curing of 28 days age of control mix compressive strength was considered the related mix, and from this, different blends with changing percentages are compared, as shown in Fig. 29, a split cylinder test was completed on cylindrical samples of 300 mm height and 150 mm diameter and at the ages of 7, and 28 days of curing.It is a technique of evaluating the concrete tensile strength using a cylinder. According to ASTM C496-7130. Past examinations have demonstrated that the consideration of fibers fundamentally enhances the split tensile strength of lightweight aggregate concrete32. In the present examination, the addition of glass fibers and silica fume to coconut Shell concrete applies a gainful impact on split tensile and flexural strength. After the test, it was noted that concrete achieved its highest flexural and split tensile strength at 45% coconut shell aggregate, 1.5% glass fibers, and 15% silica fume. Although it has been revealed that surplus quantity of coconut shell aggregates reduces strength due to poor bond between cement paste resulting in porous concrete13. Increasing the percentages of the above materials reduced the concrete split and tensile flexural strength. Fibers are mixed in concrete to increase the flexibility of concrete by halting the onset of tension cracks or preventing the generation of cracks in such a manner that the tensile strength of (SFRC) steel fiber reinforced concrete displays better conduct than normal concrete. Fibers assists in dispensing the applied forces to the whole body of concrete. Fibers are known to enhance the tensile capacity of post-cracking behavior33. Fibers have shown more substantial effects on split tensile and flexural strength at 0.5 to 2.0 percent volume fractions added in the study34. Moreover, Silica fume particles are 100 times smaller than cement grains and so they can pack very well with cement grains. They also react with CH to form CSH which gives additional binding properties and results in strength increase. However, at higher dosage Mix 4 , the workability of concrete decreases, because the size of silica fume is so small, when we add more silica fume it will increase the surface area and demand more water and if we add more water it will reduce the strength.Figure A relative analysis was carried out in which the curing age of the 28-days control sample split tensile strength was considered the related mix, and from this, different blends with changing percentages are compared, as shown in Fig. Comparison of predicted values with experimental tensile strength values utilizing ACI-318.11 codes is displayed in Fig. 2 > 0.94) amid both strengths.It is observed that entire empirical values locate well in anticipated values utilizing ACI-318.11 codes. Regression models between experimental values of split tensile strength and compressive strength are displayed in Fig. 35.Density is an indirect method to determine the durability of concrete i.e. higher density gives more dense concrete leading to fewer voids resulting in more durable concrete. Concrete density with varying percentages of different dosages was determined as per ASTM C13833. Furthermore, silica fume enhances density due to pozzolanic reaction i.e. giving secondary C–S–H gel which rises the paste viscosity leading to more packed concrete. However, mix 4 , shows less density than the control specimen. The density of coconut shell aggregate is less than coarse aggregate, and if we add more quantity of coconut shell aggregate it will lead to concrete with less strength than the control specimen.Figure 2 value greater than 90%.As density directly affects strength. Higher density gives more dense concrete leading to less void which ultimately increases strength. Therefore, a strong correlation is existing between density and compressive strength. The correlation between compressive strength and density is displayed in Fig. 32. Subjective evaluation of concrete strength and degree of concrete in various areas of members of structure might be accomplished by utilizing this technique. Any depth of surface cracks, concrete cover examination, lack of coherence in the cross-section . UPV test of all mixes was estimated, and, the relationship between the UPV and compressive strength of CS concrete was calculated at 28 days as shown in Fig. 36. Whole concrete samples were exposed to the Ultrasonic Pulse Velocity test earlier than the destructive tests. Overall, the values of the ultrasonic pulse velocity Test of entire blends improved with rising compressive strength. The values of the ultrasonic pulse velocity test entire blends are between 3.76 and 4.21 km/s. So, it can be observed from the test, that the coconut shell concrete with glass fibers have more ultrasonic pulse velocity values.It is a non-destructive test performed to evaluate concrete integrity and homogeneity as per ASTM C 597-02fck represents compressive strength in (Mpa), and v is the UPV (km/s).Ultrasonic pulse velocity calculations corresponding to their related compressive strength are shown in Fig. 2 greater than 90 percent.Regression models between Ultrasonic Pulse Velocity and experimental values of compressive strength show a strong correlation having RWater absorption is an indirect measurement of concrete durability. Mostly harmful chemicals are present in water. These chemicals react with concrete ingredients, which changes the properties of concrete. Extra water present in the pores of concrete results in freezing and thawing cycles effect because of the change in temperature, which results in a concrete crack. Therefore, a water absorption test was conducted on all samples at 7 and 28 days.13. Fibers behave as crack arresters and don’t prevent cracks which prevent cracks from propagation in the concrete leading to more strong concrete resulting in less water absorption33. Furthermore, silica fume enhances density due to pozzolanic reaction i.e. giving secondary CSH gel which enhances the paste viscosity that results in more dense concrete which also contributes to decreasing water absorption. However, mix 4 , shows more water absorption than the reference sample. the porosity of coconut shell aggregate is more than coarse aggregate, and if we add more quantity of coconut shell aggregate it will absorb more water than it should, and surplus water in the concrete is not good and it leads to multiple issues like honeycombing in concrete, porous concrete, and concrete with less strength and durability, hence it is recommended to utilized optimum quantity (45%) of coconut shell aggregate in concrete to make concrete suitable for structural application and eco-friendly.Water absorption test results are displayed in Fig. 2SO4), etc. In this study, Sulfuric acid was taken as an acid strike, on a concrete sample with different dosages. The test outcome after exposure to acid is shown in terms of mass loss because of the H2SO4 attack on the specimens after 7 and 28 days for each blend as shown in Fig. 38. Erosion speed will largely depend on sulfuric acid penetration rate into the concrete body and to reach calcium aluminate and calcium hydroxide. Therefore, improvement in the concrete porosity leads to increased density of concrete because of the addition of glass fibers. The rise in density would lead to less penetration rate of sulfuric acid in concrete. Although it has been reported that coconut shell aggregate reduces strength because of the poor bond between CS aggregate and cement paste resulting in porous concrete which decreases density13. Fibers behave as crack stoppers and not as cracks prevention which decreases void in hardening concrete leading to more dense concrete resulting in more dense concrete33. However, mix 4 , shows more weight loss than the control/ blank mix. It is because at higher dosage , the workability of concrete decreases which increases compaction efforts resulting porous concrete leading to less density which ultimately increases loss of the weight.Strong acids can be found in different varieties, for example, nitric acid, hydrochloric acid, acetic acid, and sulfuric acid  test, it was revealed when the glass fibers are added to concrete, it improves the bonding between the binder matrix and the glass fibers leading to denser and less porous concrete. Glass fibers also prevented the cracks from propagation in concrete hence increasing concrete mechanical properties.The effects of utilizing coconut shell aggregate, glass fibers, and silica fume at different percentages on the mechanical attributes and durability aspects of waste CS concrete are considered. From the trial examination, the following interpretations are obtained.Using only coconut shell as coarse aggregates in replacement of crushed aggregates may result in mediocre strength concrete with mediocre durability properties, now using glass fibers and silica fume which are both industrial waste materials or by-products will significantly enhance concrete strength, and will not cost as much, and helps the environment by effectively utilizing waste products. Coconut shell glass-fiber-reinforced concrete with silica fume is a reasonable option to be used as a feasible construction material that is sustainable in the making of concrete for structural applications, which is environmentally friendly, low cost, and has good strength.


In this study, we examined the hypothesis that cyclophosphamide (CY), a chemotherapeutic agent with the capacity to eliminate tumor infiltrating Tregs, abrogated BLM-induced expansion of Tregs and consequently resulted in a better anti-tumor effect.Promotion of the proliferative expansion of CD4in vitro effects of BLM, with or without mafosfamide , on both TGF-β-induced differentiation of Tregs (iTregs), and TNF-induced expansion of naturally occurring Tregs (nTregs) were assessed. The in vivo effect of low doses of BLM and CY on tumor-infiltrating Tregs, as well as on the growth of mouse B16-F10 melanomas, was also studied.The In vitro treatment with BLM promoted the differentiation of iTregs, as well as TNF-induced expansion of nTregs. These effects of BLM were completely abrogated by MAF. Furthermore, in the mouse B16-F10 melanoma model, treatment with low doses of BLM increased the number of tumor-infiltrating Tregs, and this effect of BLM was also abrogated by CY. Importantly, combination therapy with low doses of BLM and CY showed synergistic anti-tumor effects.CY abrogated the effect of BLM on the expansion of Tregs. The combination of these 2 chemotherapeutic agents may represent a safer and more effective therapy in the treatment of cancer patients, and thus merits future clinical evaluation. BLM is used in the treatment of different types of cancer, including skin carcinoma, lymphoma, ovarian cancer, and non-small cell lung cancer2. BLM lacks bone marrow toxicity3, but can induce idiopathic pulmonary fibrosis (IPF) in patients, which hampers its clinical use5. One strategy to mitigate its toxic effect is to use low doses of BLM in conjunction with other chemotherapeutic agents7. This combination therapy is able to preserve the anti-tumor effect of BLM while only causing minor and reversible lung injury8.Bleomycin (BLM) is a glycopeptide antibiotic derived from the bacterium, Streptomyces+Foxp3+ regulatory T cells (Tregs), presumably by stimulating the production of TGF-β10. There is compelling evidence that Tregs represent a major immunosuppressive mechanism in cancer immune evasion12. Thus, expansion of Tregs can offset the anti-tumor effect of BLM13. Indeed, it was shown that depletion of Tregs enhanced the anti-tumor effect of BLM9. Furthermore, expansion of Tregs exacerbated BLM-induced pulmonary fibrosis14. Therefore, addition of a therapeutic agent with the capacity to eliminate Tregs may further enhance the anti-tumor effects of BLM while reducing lung injury induced by BLM. Cyclophosphamide (CY) has the capacity to selectively reduce the number of highly immunosuppressive tumor necrosis factor receptor 2 (TNFR2)-expressing Tregs in the tumor microenvironments15. We therefore determined if CY abrogated the expansion of Tregs induced by treatment with BLM, to consequently enhance its anti-tumor effect.Another major adverse effect of BLM treatment is its capacity to induce expansion of CD4in vitro. This effect of BLM was abrogated by mafosfamide (MAF), the active metabolite of CY16. We confirmed that in vivo treatment with BLM at a relatively low dose induced the systemic expansion of Tregs in mouse malignant tumor models, including B16-F10 melanomas. This effect of BLM was abrogated by treatment with CY. Importantly, a combination of BLM and CY resulted in a synergistic anti-tumor effect. The results provided evidence that a combination of low doses of BLM with CY may be a novel therapeutic approach in the treatment of cancer patients.In this study, we report for the first time that BLM promoted the differentiation of TGF-β-induced Tregs (iTregs) and stimulated the expansion of naturally occurring Tregs (nTergs) induced by TNF Female C57BL/6 mice (8–12 weeks of age) were obtained from the Jackson Laboratory , and were maintained under specific pathogen-free conditions in the Animal Facility of the University of Macau. The animal research protocol was approved by the Animal Research Ethics Committee of the University of Macau.Dulbecco’s Modified Eagle Medium supplemented with 10% fetal calf serum, 100 units/mL penicillin, and 100 µg/mL streptomycin at 37 °C and 5% CO2 in a humidified incubator.Both mouse Lewis lung carcinoma (LLC) and mouse melanoma B16-F10 cell lines were purchased from the American Type Culture Collection . The LLC and B16-F10 cell lines were cultured in Bleomycin sulfate was purchased from Ark Pharm . Cyclophosphamide monohydrate was purchased from Sigma-Aldrich . Mafosfamide sodium salt was purchased from Santa Cruz Biotechnology . Antibodies including PerCP-Cy5.5 anti-mouse TCRβ (H57-597), PerCP-Cy5.5 anti-mouse CD4 (RM4-5), and PE anti-mouse CD120b  were purchased from BD Pharmingen . Antibodies termed PE-Cy7 anti-mouse CD4 (GK1.5), eFluor 450 anti-CD4 (RM4-5), PerCP-Cy5.5 anti-mouse CD45 (30-F11), APC anti-mouse/rat Foxp3 (FJK-16s), mouse TGF beta 1 Recombinant Protein (rmTGF-β), and Foxp3/Transcription Factor Staining Buffer Set were purchased from Invitrogen . Anti-CD3, anti-CD28, anti-Recombinant Mouse TNF (rmTNF), and rmIL-2 were purchased from BD Pharmingen . The LIVE/DEAD Fixable Near-IR Dead Cell Stain Kit and CellTrace™ Violet were purchased from Thermo Fisher Scientific .+ T cells were isolated from lymphocytes of C57BL/6 mice using Mouse CD4 (L3T4) MicroBeads and MS Columns . The purity of the isolated cells was > 95%. In a U-shaped 96-well plate, cells (1 × 105 cells/well) were subsequently activated by plate-coated anti-CD3e antibody (1 µg/mL) and soluble anti-CD28 antibody (0.5 µg/mL), with rmTGF-β (5 ng/mL). BLM or MAF was added into wells as indicated. After culturing for 2 days, the cells were collected, fixed, and permeabilized. Foxp3 expression by CD4+ cells was determined by flow cytometry.CD4+ T cells (1 × 106 cells/well) were stimulated with rmIL-2 (0.25 ng/mL) plus rmTNF (5 ng/mL), in the presence or absence of BLM or MAF. After culturing for 3 days, the cells were collected, fixed, and permeabilized. The replicating Foxp3+ CD4+ T cells and the expression of TNFR2 were analyzed by flow cytometry.In a U-shaped 96-well plate, CellTrace™ Violet-labeled CD42)/2. Treatment was started on day 6 after tumor inoculation. LLC tumor-bearing mice were treated intravenously (i.v.) with BLM (2 mg/kg in PBS) every 3 days for a total of 4 times. B16-F10 melanoma-bearing mice were treated with BLM  every other day for a total of 4 times. For BLM and CY combination therapy, BLM  was administered every 3 days for 4 times, starting from day 6 after inoculation of B16-F10 melanoma cells, and CY  was administrated every 3 days by intraperitoneal injection for 4 doses starting on day 7 after inoculation. On day 17 after tumor inoculation, the mice were euthanized and their spleens, lymph nodes, and tumor tissues were harvested for fluorescence-activated cell sorting (FACS) analysis and identification of Tregs.LLC or B16-F10 melanoma cells  were injected subcutaneously into the right flank of C57BL/6 mice. Tumor size was calculated using the formula:  is shown in Supplementary Figure S1.After blocking Fc receptors, the cells were incubated with appropriately diluted antibodies and finally suspended in fluorescence-activated cell sorting (FACS) buffer for cytometric analysis. Acquisition was performed using BD LSRFortessa flow cytometry . FlowJo software  was used for data analysis. The gating strategy for tumor infiltrating Tregs . A P value < 0.05 was considered to be statistically significant.All data are presented as means ± SD. The statistical analysis was performed using a 9, and that this dose of BLM was toxic and could cause lung injuries17. To determine the effect of BLM on Tregs using a nontoxic dose to the lungs, B16-F10 melanoma-bearing mice were injected i.v. with 2 mg/kg of BLM every other day for 4 times, starting from day 6 after tumor cell inoculation . We confirmed that BLM with this low dose did not cause lung injuries , and that this treatment did not result in inhibition of B16-F10 melanoma tumor growth . However, the percentage of Foxp3+ cells in CD4+ T cells was increased in the spleen, blood, and tumor tissue by 15%–50% in mice treated with BLM . The absolute number of Tregs in the spleen was also increased by BLM treatment . Similar observations were made in mice bearing LLC Lewis lung cancers, although treatment with BLM resulted in increased inhibition of tumor growth . Together, the results showed for the first time that, even at a lower dose, treatment with BLM increased the number of Tregs in tumor bearing mice.It was reported that treatment with BLM at 20 mg/kg resulted in the expansion of Tregs in mice bearing CT26 colon cancers+ T cells into iTregs or from the proliferative expansion of pre-existing nTregs20. To clarify the mechanism underlying the effect of BLM on the expansion of Tregs, we examined the effect of BLM on the differentiation of iTregs. To this end, purified CD4+ T cells were activated with anti-CD3 and anti-CD28 antibodies, in the presence of TGF-β, for 48 h, and the number and the percentage of Foxp3-expressing Tregs were determined. Figure 2A shows that TGF-β-induced Foxp3 expression in CD4+ T cells was enhanced by BLM over concentration ranges of 100–500 ng/mL (P < 0.001–0.01). The absolute number of Tregs was also increased by BLM treatment (P < 0.001–0.01).Increases in Tregs could have resulted from either the conversion of naïve CD4in vitro studies16. We found that MAF (0.5–2 µg/mL) inhibited BLM-induced increases in Tregs, including both the percentage of Foxp3+ cells in CD4+ T cells  and the absolute number of Tregs . Thus, MAF inhibited BLM-induced differentiation of iTregs.MAF is a derivative of CY, which is active without being further metabolized. So it can be used for in vitro stimulation with TNF resulted in the preferential proliferation of pre-existing nTregs present in CD4+ T cells23. We therefore determined the effect of BLM on nTreg expansion in this experimental setting. To this end, purified CD4+ T cells were cultured in IL-2-containing medium (0.25 ng/mL) to maintain the survival of Tregs. The proliferation of Tregs was assessed by gating of Foxp3+ cells, based on the dilution of CellTrace™ Violet. Figure 3A shows that the addition of TNF (5 ng/mL) resulted in a 44% increase in proliferation of Tregs (P < 0.001). Notably, the proliferation of Tregs and TNFR2 expressions of Tregs induced by TNF was further increased by treatment with BLM . This effect of BLM was inhibited by MAF at concentrations starting from 0.5–1 µg/mL , showing that BLM also promoted the proliferation of nTregs, which was abrogated by treatment with MAF.By stimulating TNFR2, we previously reported that in vivo effect of BLM on Treg expansion and consequently enhanced its anti-tumor effect. To this end, B16-F10 melanoma-bearing mice were injected i.v. with BLM (2 mg/kg) every 3 days starting from day 6 after tumor inoculation, for a total of 4 doses. The mice were also injected i.p. with CY (50 mg/kg) for 4 doses, every 3 days starting from day 7 after tumor inoculation . On day 17 after tumor inoculation, the mice were sacrificed and the percentages of Tregs in the spleen, draining lymph nodes (dLNs), non-draining LNs (ndLNs), mesenteric LNs (mLNs), and tumor tissues were analyzed by flow cytometry. Figure 4 shows that monotherapy with CY decreased the percentages of Tregs in lymphoid tissues and the blood (P < 0.01–0.05), as compared with PBS treatment. Importantly, increases in the percentages of Tregs in the spleen (4B–C), dLN (4E), ndLN (4F), mLN (4G), and blood (4H) were completely abrogated by treatment with CY . Treatment with CY also reduced the number of Tregs in the spleen in BLM-treated mice .We next determined if CY abrogated the + T cells was 34.1%, which was increased by treatment with BLM to 50.4% and decreased by treatment with CY to 14.8% . Importantly, the increase of Tregs in BLM-treated mice was completely abrogated by CY treatment  . We have previously reported that TNFR2 was associated with a highly suppressive phenotype of Tregs, and that this marker was characteristically expressed by the majority of tumor-infiltrating Tregs24. Consistent with a previous report15, CY treatment, alone or with BLM, also reduced the number of TNFR2-expressing Tregs in tumor tissues  (P < 0.05), suggesting that CY reduced the number of tumor infiltrating Tregs and also decreased their suppressive capacity and proliferative expansion.The percentage of Tregs in tumor infiltrating CD4Figure 6 shows that monotherapy with CY or BLM only resulted in a modest inhibition of B16-F10 growth of melanomas in mice (P > 0.05). However, the combination of BLM and CY resulted in an enhanced inhibition B16-F10 melanoma growth  (P < 0.001–0.05). Compared with the PBS-treated group, the tumor weight was decreased 80% after combination therapy  (P < 0.01). In addition, we confirmed that BLM alone at doses used in this study or in combination with CY did not cause lung injuries . Together, the results showed that BLM and CY showed excellent efficacy for the growth inhibition of mouse B16-F10 melanomas.We further determined the effect of combination therapy of BLM and CY on the growth of B16-F10 melanomas in syngeneic C57BL/6 mice. 26. In addition to decreasing anti-tumor immune responses, expansion of Tregs induced by BLM may cause the development of IPF14. Thus, CY may also ameliorate BLM-induced IPF through elimination of Tregs. To mimic the clinical application, our study used a relatively low dosage of BLM that did not cause lung injuries. However, further investigation is required to completely evaluate the effects of CY on BLM-induced IPF in an appropriate animal model.In this study, we clearly showed that CY was able to completely eliminate the stimulatory effect of BLM on Tregs, and consequently improve its anti-tumor efficacy. IPF is a major complication of BLM treatment in cancer patients9. In this study, we determined the protein levels of TGF-β in the serum of melanoma-bearing mice, but failed to find any difference in response to BLM treatment (data not shown). This may be because we used a lower dosage of BLM in our study, as compared with that in a previous report9. Furthermore, induction of TGF-β production by BLM is a time-dependent event27, and we may not have measured this cytokine at an optimal time frame. In addition, serum may not reflect the tissue levels of TGF-β. Nevertheless, we found that the level of TNF in the serum of BLM-treated melanoma-bearing mice was increased (data not shown). This result is consistent with previous reports showing that high levels of TNF were induced by BLM in a mouse lung injury model28. To identify the mechanism underlying the stimulatory effect of BLM on Treg expansion, we examined the effect of BLM on the differentiation of iTregs induced by TGF-β and on the expansion of nTergs induced by TNF in vitro. To this end, unfractionated CD4+ T cells were used because, similar to naïve CD4+ T cells, their Foxp3 expression can be induced and upregulated by TGF-β29. Furthermore, the number of Foxp3-expressing Tregs in CD4+ T cells can be expanded by TNF stimulation in a similar manner as in purified CD4+Foxp3+ Tregs21. The results of our study for the first time showed that BLM had the capacity to promote in vitro iTreg differentiation and nTreg expansion. Because BLM treatment was able to increase TNF levels in mouse serum (data not shown) and CY, an agent known to eliminate TNFR2-expressing Tregs15, was able to abrogate this expansion of Tregs in BLM-treated mice, we hypothesized that the enhanced interaction of TNF-TNFR2 was responsible for the expansion of Tregs by in vivo BLM treatment. Nevertheless, we could not exclude the possibility that promotion of both iTreg differentiation and nTreg expansion collaboratively contributed to the increased number of Tregs in BLM-treated mice.It was previously reported that BLM-induced increases in Tregs were associated with upregulation of TGF-β mRNA expression+ T cells, CD8+ T cells, and Gr1+CD11b+ myeloid-derived suppressor cells (MDSCs) in the spleen of BLM-treated mice (data not shown). This is consistent with a previous report9. It was also reported that BLM increased the number of INFγ+CD8+ CTLs in a mouse tumor model9. We confirmed this observation and found that BLM treatment enhanced the number of tumor-infiltrating IFNγ-expressing CD8+ T cells in B16-F10 melanoma-bearing mice (data not shown). However, our results did not show a further enhanced expansion of INFγ+ CTLs after CY treatment (data not shown). Presumably, BLM treatment at the dose used in this study achieved a maximal expansion of INFγ+ CTLs and thus any additional effect of CY could not be detected.Although BLM enhanced the number of Tregs, we were not able to detect any alteration in the proportion of CD430. Among these Treg-eliminating chemotherapeutic agents, the effect of CY has been well-studied, providing compelling evidence that it eliminated tumor-associated TNFR2-expressing Tregs in both human patients and in mouse tumor models15. In this study, the combination of BLM and CY showed a synergetic anti-tumor effect on mouse B16-F10 melanomas. Although this effect was likely attributable to the reduction in Tregs, other actions of these 2 chemotherapeutic agents cannot be excluded. For example, it is known that BLM causes DNA breaks similar to the effect of radiotherapy31. Active metabolites of CY can cause DNA cross-linking and thus result in cell death16. Furthermore, both BLM and CY have been shown to induce immunogenic cell death32. The contribution of these effects of BLM and CY to the observed synergistic anti-tumor action should be addressed in future studies.Recent studies have shown that some chemotherapeutic agents eliminated Tregs in cancer patients. For example, docetaxel and gemcitabine can deplete circulating TregsTaken together, our study showed that CY completely abrogated the expansion of Tregs induced by BLM. This effect may be, at least partially, responsible for the synergistic effect of BLM and CY in the treatment of mouse B16-F10 melanomas. Our results suggested that these 2 chemotherapeutic agents may represent a safer and more effective combination therapy for the treatment of cancer patients, and thus merit future study.Click here for additional data file.


This website for the Center for Disease Control highlights their investments in responding to antibiotic resistance. One interesting resource is a large strain collection of resistant isolates that can be accessed for research purposes.This page of the Pew Trust lists provides links to ongoing projects for new antibiotic development.This page from the Royal Society is for a scientific meeting on the subject. A link is provided to a report on the meeting.This MIT News page describes the development of a model trained on known antimicrobial substances to predict the efficacy of new compounds from a chemical library. Subsequent testing showed the effectiveness of the approach.This page from the World Health Organization provides a good overview of global concerns and research regarding antimicrobial resistance.MIBiG is a data repository for natural product gene clusters of known functions. This serves as an important tool for uncovering the functions in new gene clusters that will provide the basis for future antimicrobials.Pharmaceuticals that is scheduled to be published in this coming year, 2022.This is the webpage for a special issue of the journal This recent review article summarizes technical advances that are promoting new natural product drug discovery, including antimicrobials.This page represents a large group of scientists working in the area of natural products and has many links to publications and resources.This recent review highlights new developments in generating pipelines for new antibiotic discovery and implementation.