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Knowledge of shear friction material properties is central to the design of reinforced concrete elements. These shear friction properties are impacted by components of concrete mix design that impact the roughness of a cracked plane, including the strength of the mortar and aggregates. In this paper, 72 shear friction tests are undertaken on multigeneration recycled aggregate concrete that successively crushes and reuses concrete to make three generations of aggregate. The results of these tests are brought together with 314 existing shear friction test results on virgin and recycled aggregate concrete to develop a new unified model to predict the shear capacity of initially uncracked concrete. The results of the modeling show that even after multiple generations of recycling aggregate, no significant decline occurs in the shear strength of concrete and that the shear strength is most strongly influenced by the confining stress. The analysis of the test results across multiple studies identifies critical areas for future research, including the need for better reporting of actual confining stresses and the reporting of crack widths to allow for a more complete understanding of behavior. [ABSTRACT FROM AUTHOR]

Eco-friendly armor units and coastal structures provide a sustainable alternative to traditional design by incorporating eco-enhancing aspects into the design process to enhance biodiversity in their vicinity. ECOncrete's Coastalock armor units feature a nature-inclusive design utilizing a bio-enhancing concrete mix, and biological surveys from a pilot deployment have already shown their positive impact in this sense. A comprehensive research program was initiated by the University of Ottawa and the Ocean, Coastal, and River Engineering Research Center of the National Research Council of Canada (NRC-OCRE), in collaboration with ECOncrete, a science-based bio-enhancing concrete technology company. Two-dimensional physical model tests of a low-crested and emergent rubble mound breakwater, each armored with Coastalock units, were conducted in the Large Wave Flume at the NRC-OCRE. Testing was conducted at a 1/15 scale. Both models were constructed as permeable structures with uniform 2V:3H front and back slopes and exposed to irregular waves with significant wave heights ranging between 0.08 and 0.38 m (1.2 and 5.7 m at prototype scale), while the wave steepness ranged between 0.03 and 0.07. This study focused on Coastalock armor unit placement, spacing, and underlayer rock size to understand their impact on hydraulic stability. The hydraulic performance of Coastalock armor units was analyzed by investigating wave transmission using existing formulas in the literature. Overall, the Coastalock armor units exhibited commendable stability against diverse wave conditions. [ABSTRACT FROM AUTHOR]

This article presents the results of a preliminary study of concrete samples with pine chips: the search for the optimum proportion of concrete mixture and waste in the mix, its workability, and the mortar’s bending and compressive strength. By building on the properties of the concrete mix, which reaches its maximum strength value with time, the preparation time of plates is reduced by the pressing and drying process. The effect of the percentage of chips in the mix and the effect of chip fraction on mortar strength - bending test and stretching test are used. The research is conducted to determine the possibility of reusing wood waste in fibre-cement composites for construction applications. Depending on the chip fraction, they gained positive characteristics, the beam with a finer fraction achieved greater strength, similar to a concrete beam. Unground chips, on the other hand, maintained the bond, which did not occur in the finer fraction. [ABSTRACT FROM AUTHOR]

The optimization of metakaolin (MK) in pre-cured geopolymer concrete involves developing predictive models to capture the interplay of various influencing factors and guide mix design for improved compressive strength and sustainability. Ensemble methods and symbolic regression are promising approaches for this task due to their complementary strengths and solving challenges associated with repeated experiments in the laboratory. Choosing machine learning predictions over repeated, expensive, and time-consuming experiments in research projects, such as optimizing the utilization of metakaolin in pre-cured geopolymer concrete, presents a paradigm shift in how data-driven insights can revolutionize material development. The integration of ensemble and symbolic regression models enables researchers to derive valuable predictions and optimize critical performance parameters efficiently. In this research work, 235 records were collected from extensive literature search for compressive strength for different mixing ratios of pre-cured metakaolin-based geopolymer concrete with concrete at different ages. Each record contains MK: The content of metakaolin (kg/m3), SHS: Sodium hydroxide solution content (kg/m3), SHSM: Sodium hydroxide solution molarity (Mole), SSS: Sodium silicate solution content (kg/m3), W: Extra water content (not including the water in alkaline solutions) (kg/m3), W/S: Water to Solid ratio (Total water content / Solid part of activator solutions + MK), Na2O/Al2O3: Sodium oxide to aluminium oxide ratio, SiO2/Al2O3: Silicon oxide to aluminium oxide ratio, H2O/Na2O: Water to Sodium oxide ratio, CA/FA: Coarse to Fine aggregate ratio, CAg: The content of coarse aggregates (kg/m3), SP: The content of super-plasticizer (kg/m3), PCC: 0 for no pre-curing, 1 for pre-curing at 60 °C, and 2 for pre-curing at 80 °C, CT: Curing temperature (°C), Age: The concrete age at testing (days) and CS: Compressive strength (MPa). The collected records were portioned into training set (180 records≈75%) and validation set (55 records≈ 25%) and modeled with ensemble and symbolic regression methods. At the end of the model work, performance metrics were used to evaluate the models' ability and Hoffman and Gardener's sensitivity analysis was used to evaluate the impact of the variables on the compressive strength of the pre-cured geopolymer concrete mixed with metakaolin. GB and KNN models became the decisive models with excellent performance which outclassed others and the sensitivity analysis indicated that SHSM, SSS, W/S, and Na2O/Al2O3 are the most influential to the predicted compressive strength. [ABSTRACT FROM AUTHOR]

Geopolymer concrete (GPC) can be produced by the chemical activation of industrial by-products and processed natural minerals that contain aluminosilicates with the presence of an alkaline activator. Raw components are one of the critical parameters affecting geopolymer performance. On the other hand, the mixing procedure of geopolymer concrete is not any less important. Few demonstrative constructions have been built using GPC as a greener alternative to Portland cement concrete. Numerous variables affect GPC manufacture, such as raw material specification, activator type and dosage, and curing regimes. Despite the conventions of the building industry, the lack of proper mix design methods limits the wide acceptance of GPC in the industry. This report conducted experimental trials on GGBS-based GPC to optimize a mixing design procedure to achieve best mechanical strength and structural integrity. Geopolymer concrete properties were evaluated through slump and unconfined compressive strength tests. The laboratory trials in this report revealed that all geopolymer mixes, except SD0HV and 1W-SG, exhibited high workability values. Also, the presence of an alkaline activator was vital to attain satisfactory compressive strength values. The alkaline activator could be used when cooled and reached room temperature after two hours of preparation and was not necessary after 24 h. Mix G-(0.5W-S) with a 0.5A.A. (alkaline activator)/precursor (GGBS) ratio, SSA (sodium silicate alternative)/SH (sodium hydroxide with 10 M molarity) ratio of 1:1, and 0.55 W/B (water to binder) ratio is recommended to achieve best mechanical performance and structural integrity. [ABSTRACT FROM AUTHOR]

During the manufacture of high-strength concrete, its sensitivity to variations inconcrete mixing water, the poor adaptability of cement, and high hydration temperatures are often encountered. Therefore, in this paper, firstly, the esterification reaction of methoxy polyethylene glycol ether (MPEG) and methacrylic acid (MAA) was carried out. According to the different molecular weights of MPEG, three kinds of esterification products (MPEG-MAA) were synthesized. Three kinds of PCE-st were synthesized by free-radical copolymerization of three kinds of MPEG-MAA, ethylene glycol polyethylene glycol ether (EPEG), and acrylic acid (AA), and their effects on the properties of cement paste and concrete were analyzed. The results revealed that when the water–cement ratio increased from 0.25 to 0.31, PCE-st with MPEG with a molecular weight of 600 optimally reduced the water content variation sensitivity and increased the fluidity of cement pastes by only 62 mm, while PCE-st with smaller and larger molecular weights of MPEG increased the fluidity by 94 mm and 80 mm, respectively. As the molecular weight of MPEG increased from 400 to 1200, the hydration temperature decreased from 43.8 °C to 39.5 °C, and the setting time was delayed by about 30 min. Finally, the compressive strength of concrete made with PCE-st was similar to that of the concrete made with commercially available PCE-et0. [ABSTRACT FROM AUTHOR]

Concrete, which forms the skeleton of buildings, is the most important building material to ensure the continuity of a building's durability and to survive a possible earthquake. Concrete durability is directly related to its constituent materials. In this study, it was investigated how concrete aggregate and chemical admixture change the strength of concrete according to their type. The research question of this study is: what is the place and importance of aggregate and chemical admixture in increasing concrete strength? Recent earthquakes, especially in Turkey, have shown that most of the buildings that collapsed had poor-quality concrete. The aim of this study is to determine the concrete mix designs for the production of superplasticizer concrete for the production of concrete with the desired strength depending on the tested parameters. In this study, the effect of the parameters that make up the tested concrete content on concrete strength was investigated both experimentally and statistically. Water–cement ratio, aggregate type, Los Angeles abrasion resistance of aggregates, aggregate–cement ratio and new-generation polycarboxylate-supported superplasticizer chemical admixture are the parameters in the concrete content. Statistical analysis was carried out with SPSS, an up-to-date software, using the experimental findings. There was a very good agreement between both measured and predicted values. The equations with a coefficient of determination R2 > 0.96 were derived. The developed statistical method was found to be unique and highly accurate. Thus, it is aimed to provide safe, economical, practical and time-saving pre-mix designs. [ABSTRACT FROM AUTHOR]

Owing to serious limitations of freshwater, using unconventional water resources such as greywater is unavoidable. Considering the large amount of water needed for making concrete, in this research, greywater was used to mix eco-friendly concrete. To investigate the appropriate quality of greywater, synthetic and real greywater samples were prepared, and pH, total dissolved solids (TDS), chemical oxygen demand (COD), chloride (Cl−) and sulfate (SO42−) contents were evaluated. Based on a concrete performance index, the maximum appropriate values of COD, TDS and sulfate were determined to be 119, 411 and 134 mg/l, respectively, and the water quality index should be over 67.5. The results of tests conducted on samples containing various types of greywater showed a decrease in mechanical performance, but not durability properties. The results revealed that the quality of concrete mainly depends on the quality of greywater according to the Pearson coefficient. The Pearson coefficient was generally greater than 0.4, revealing a strong correlation between greywater quality and concrete characteristics. Using a combination of greywater and potable water generally provided better performance than the use of greywater alone. Based on the results, although the use of greywater can decrease freshwater consumption, supplementary tests still need to be performed. [ABSTRACT FROM AUTHOR]

Lightweight reactive powder concrete (RPC) with enhanced thermal insulation is an interesting material due to its durability and mechanical properties. This paper presents the results of tests analyzing the thermal conductivity coefficient λ of several lightweight RPCs, obtained using expanded clay, Pollytag, expanded perlite, and expanded polystyrene beads in quantity from 30% to 60% by volume. Correlations between the λ coefficient and the density of the lightweight RPCs were defined. They were compared with correlations determined for different types of ordinary lightweight concrete based on data from previous studies in the literature. It was proven that, due to the significant influence of the thermal conductivity of the RPC cement matrix, with a relatively high λ coefficient, the thermal conductivity coefficients, λ , of lightweight RPCs reach higher values. Based on the microstructure analysis, it was found that the type and number of aggregate pores have also affected the density and, in consequence, the thermal conductivity of the lightweight reactive powder concrete. The expanded clay aggregate is the most suitable material to produce structural lightweight RPC, due to its low λ coefficient and high strength. A thermal conductivity coefficient λ value of 0.93 W/(m·K) and a density of 1,630 kg/m3 were measured for an RPC with 60 vol.% of expanded clay. This RPC reached a compressive strength of 64.5 MPa after 28 days and 77.9 MPa after one year and hence can be classified as structural lightweight. The use of expanded clay in RPC allows the subsequent material to achieve a significantly higher strength compared with conventional lightweight concrete with expanded clay, with a comparable density and slightly higher thermal conductivity coefficient λ. Practical Applications: Reactive powder concrete with mineral lightweight aggregate could be an alternative to ordinary lightweight concrete with enhanced strength. Above all, the advantage of these new lightweight composites is a lack of strict dependence between the lightweight aggregate's strength and the composite's strength. Second, the water absorption of lightweight aggregate has minimal impact on RPC properties. In this case, the RPC matrix mainly influences the material's water absorption and strength. Densely packed particles in a cement matrix and close adhesion of homogeneous RPC mix, with enhanced viscosity, to lightweight aggregate as well as placement of the concrete mix in large pores on the aggregate surface cause the low water absorption of lightweight RPC, similar to the water absorption of the RPC matrix. Further, lightweight RPC achieves relatively high strength. This fact makes the design of a lightweight RPC mix easier in comparison with ordinary lightweight concrete, where the water absorption of lightweight aggregate has to be taken into account when designing the concrete mix. In the case of ordinary lightweight concrete, the shaping of its properties is more complex, the designing of its composition is more complicated, and the production technology is more time-consuming, subjected to a greater risk of error. [ABSTRACT FROM AUTHOR]

This study investigates the durability of concrete structures under severe environmental conditions, focusing on the effects of thermal stress, saline exposure, and seismic activity. The research employs a dual approach, combining laboratory experiments and field case studies to analyze various environmental impacts, mix designs, and the use of crystalline admixtures. Two concrete mix designs, CMD-01-C30/37 (mass concrete) and CMD-02-C35/45 (underwater concrete), were developed and tested for strength, permeability, and self-healing properties. The results demonstrate that both mix designs met or exceeded the required strength specifications, with improved resistance to water penetration and permeability depths lower than the code requirements set by European standards from EC2. The incorporation of crystalline admixtures in the mix designs significantly enhanced durability and performance, aligning with the priority of developing zero-carbon concrete solutions. The study also observed the self-healing capabilities of concrete treated with crystalline admixtures, as evidenced by the sealing of cracks at expansion and construction joints over time. These findings contribute to the development of a robust methodology for creating resilient structures adaptable to climate change, with potential implications for enhancing seismic resistance and structural longevity. The study underscores the importance of considering environmental factors and innovative admixtures in concrete design to improve durability and resilience, particularly in areas prone to seismic activity and extreme environmental conditions. Future research directions should focus on further investigating self-healing mechanisms, exploring the integration of durable and self-healing cement-based materials in engineering practice, and evaluating applications for both new construction and retrofitting existing structures. [ABSTRACT FROM AUTHOR]

Sustainability and construction waste recycling have become crucial topics today in response to the growing environmental challenges and the increasing accumulation of waste. Therefore, it is essential to explore innovative solutions that improve the sustainability of concrete mixes. An effective approach is the use of Lightweight Foamed Concrete (LFC), a revolutionary new material that is considered a viable solution for the reduction of the weight of conventional concrete. This research focuses on the study of the effect of replacing 50% of virgin sand by volume with Recycled Foam Concrete (RFC) waste crushed at four gradation levels with aggregate sizes between 12.5-9.5 mm, 9.5-4.75 mm, 4.75-2.36 mm, and 2.36-1.18 mm, and the effect of adding 0.5% Nano titanium dioxide TiO2 by weight of cement. The water-to-cement and cement-to-aggregate ratio were maintained at 0.45 and 1:1.3, respectively. Nanoparticles are incorporated into Foam Concrete (FC) to enhance its strength, due to their beneficial properties, such as their small particle size and high reactivity. The results conclude on the optimal sizes of RFC with the addition of Nano TiO2 for use in FC mixes that enhance compressive strength and increase carbonation compared to traditional FC mixes. [ABSTRACT FROM AUTHOR]

The rapid growth of infrastructure, urbanization, and industrialization has increased global concrete demand, putting pressure on natural resources and creating ecological challenges. In response, using Brick Waste (BW) as a substitute for natural aggregates in concrete offers a promising solution to enhance sustainability in construction materials. This study specifically investigates the replacement of Natural Coarse Aggregates (NCA) with Brick Coarse Aggregates (BCA) at substitution rates of 25%, 45%, 65%, and 85%. The experimental results show that replacing 25% of NCA with BCA leads to a 12% decrease in workability and a 2.48% reduction in density compared to a control concrete mix. In its hardened state, this substitution results in a slight decrease of 6.45% in compressive strength (fc). At higher substitution rates, such as 85%, the decrease is intensified, with a 32% reduction in workability, 7.93% in density, and 50.32% in compressive strength, all compared to the control concrete after 56 days. The present study also emphasizes a significant correlation between the measured compressive strength and that estimated by non-destructive methods, such as the Schmidt Rebound Hammer Test. Optimizing substitute materials is crucial for achieving high performance while ensuring environmental benefits. This research proposes an innovative approach to sustainable construction, providing a unique opportunity to reconcile performance and sustainability in the construction sector. The importance of this work lies in its potential to transform waste management practices and promote more ecological construction materials. [ABSTRACT FROM AUTHOR]

The research object is concrete with supplementary cementitious materials (SCMs) such as bentonite clay and quarry dust. The impact of incorporating these SCMs on fresh concrete properties, compressive, flexural, and split tensile strengths, and acid resistance was investigated. Microstructural analysis using Scanning Electron Microscopy (SEM) and X-ray radiography were used. Varying proportions of SCMs (5%–20%) were incorporated into the concrete mix while maintaining a constant water-to-cement ratio. Key findings reveal a 7.31% increase in compressive strength, a significant 19.7% improvement in flexural strength, and enhanced acid resistance. Utilizing Response Surface Methodology (RSM), the optimal mix design for achieving superior mechanical strength was identified. The quadratic model of RSM indicated that a combination of 10.29% bentonite clay, 7.20% quarry dust, and 8.19% fine aggregate replacement yielded the highest strength. Predictive and experimental results demonstrated strong agreement. Compared to the reference concrete, the optimized samples exhibited significant increases of 18.08%, 33.60%, and 11.15% in compressive, flexural, and tensile strengths, respectively. This research demonstrates the potential of locally available SCMs as viable and sustainable alternatives for concrete production, offering improved performance without compromising strength. [ABSTRACT FROM AUTHOR]

The incorporation of desert sand-mineral admixture improves the abrasion resistance of concrete. To prolong the service life of assembled concrete channels and mitigate the depletion of river sand resources, the effects of fly ash (FA), silica fume (SF), desert sand (DS), and basalt fiber (BF) on the mechanical properties and the abrasion resistance of concrete were examined, alongside an analysis of their microstructures to elucidate the underlying mechanisms of influence. The results indicated that the abrasion resistance strength of concrete mixed with 10% FA and 0.05% BF alone increased by 80.19% and 81.59%, respectively, compared with ordinary concrete (OC). When SF was added to the concrete at a dosage of 10%, it improved the mechanical properties and the abrasion resistance of the concrete. Furthermore, adding SF resulted in a 12.50% increase in compressive strength and a 12.27% increase in abrasion resistance strength compared to OC. The addition of DS did not significantly enhance the concrete's abrasion resistance. The combination of ingredients for desert sand concrete (DSC) that provides excellent abrasion resistance was determined using an orthogonal experiment. The optimal mixture consisted of 10% FA content, 10% SF content, 40% DS content, and 0.05% BF content, which increased the abrasion resistance strength by 112.95% compared to OC. Through microscopic analysis, it is found that the width of the interfacial transition zone (ITZ) is an important factor in determining the abrasion resistance of concrete, and a narrower ITZ enhances the concrete's abrasion resistance. The study's findings could function as a theoretical reference for the engineering design of DSC. [ABSTRACT FROM AUTHOR]

To thoroughly study the stress–strain relationship of lightweight mixed ceramic concrete, this paper conducts axial compressive strength tests on three groups of lightweight mixed ceramic concrete specimens with different types and contents as the basis. It establishes the elastic modulus calculation formula and compressive stress–strain formula for lightweight mixed ceramic concrete by combining with the current standards and related research. The results show that lightweight mixed ceramic concrete, made of a mixture of different types and densities of ceramic grains, has better mechanical properties and deformation properties. The calculation errors of the modulus of elasticity formulas, derived from the experimental results for the three groups of lightweight mixed ceramic concretes, are all controlled within 5%. The average relative errors of the fitting results of stress–strain curves for the three groups of specimens and the measured data are as low as 6.66%, 3.16%, and 3.39%. The errors between the experimental values of the modulus of elasticity of different studies and the predicted values based on the formula in this paper were controlled within 17%, and the average relative errors between the predicted and experimental results of the stress–strain curves for the three groups of specimens were 2.64%, 8.94%, and 17.50%. This paper innovatively constructs a prediction model of key mechanical parameters of lightweight mixed ceramic concrete, which can provide a reference and experimental basis for the structural analysis and application of lightweight mixed ceramic concrete. [ABSTRACT FROM AUTHOR]

This study investigates the effect of calcined clays (metakaolin, metasilt, metaclay) on the chemical composition, distribution, and structure of alkali–silica reaction (ASR) gels. Using 10 wt% of calcined clays reduced concrete expansion and minimized cracking but did not inhibit ASR gel formation. Micro X-ray fluorescence mapping revealed an average ASR gel content of 3 wt% in concrete, incorporating up to two-thirds of K2O and nearly all Na2O from the binder. Raman spectroscopy indicated structural similarities among gels in different concrete mixes, with an increased degree of polymerization in the metakaolin-containing concrete. Automated mineralogy identified four gel phases: Si gel, Ca-Si gel, Al-Ca-Si gel, and Al-Si gel. Ca-Si gels are formed at binder interfaces, while non-swellable Al-bearing gels are mainly formed in metakaolin-containing concrete located within aggregates. This study shows that aluminum can be incorporated into gels in calcined clay concretes, altering their structure and potentially affecting their expansion behavior in concrete. [ABSTRACT FROM AUTHOR]

The marble industry in Afghanistan generates significant waste due to a lack of skilled labor and advanced machinery, which is often discarded in landfills. Previous studies suggest that marble waste can be utilized in construction, particularly in cement-based structures. This research investigates using marble waste in concrete as a replacement for cement and sand to address environmental concerns and promote sustainability. A comparative study replaced marble waste with a calcareous filler from Omya SAS. The marble waste, collected from a mining site in Nangarhar, Afghanistan, consisted of 29% particles smaller than 63 μm and 71% sand particles. The waste marble (WM) was added to concrete as a replacement for cement and sand at 3.5%, 4%, and 4.5% by volume. Limestone filler (LF) replaced only cement in the concrete mix. The reference concrete mix aimed for a C25/30 strength. The results showed slight improvements in concrete workability with increasing waste marble content. The optimal WM dosage was 4%, which led to a 9% reduction in compressive strength and a 7% drop in splitting tensile strength. However, this dosage reduced concrete density, improving transfer properties and resulting in cheaper, lighter concrete. The 4% WM dosage corresponds to 7.5% cement and 12% sand replacement. [ABSTRACT FROM AUTHOR]

This study focuses on exploring the potential of utilizing demolished concrete and promoting sustainable practices through the use of recycled concrete aggregate (RCA) as a substitute for natural aggregates, particularly in the context of Nepal. The region's susceptibility to frequent earthquakes results in significant volumes of concrete rubble, posing challenges in waste disposal. To address this issue and mitigate resource depletion, the research focuses on concrete recycling. By conducting a thorough analysis of mechanical properties, crack patterns, strength variations, and specific gravity evaluations across different RCA compositions, the study emphasizes the ongoing endeavors toward sustainable concrete practices. A comparative examination of test results involving varying percentages of coarse recycled aggregate content (0%, 25%, 50%, 75%, and 100%) denoted as R0, R25, R50, R75 and R100, respectively, provides insights into the performance of different mixes. The compressive strength of cube for R25 increased by 20.13%, while R50 and R75 showed gains of 8.08% and 1.28%, respectively, while cylinder showed an increase of 25.86%, 18.88%, 9.54% and 2.65% for R25, R50, R75 and R100, respectively, compared to R0 concrete mix when tested at 28 days of curing. Tensile strength of concrete cylinder also improved, with R25 showing an 18.52% increase and R50 showing a 9.26% increase. Additionally, the RCA increased the flexural strength, with R25 leading with a 5% increase and R50 following with a 1.66% increase at 28 days of testing. The inclusion of numerical analysis in ABAQUS CAE using the Kent and Park Model serves to reinforce and support the experimental findings, establishing the credibility of both approaches. In essence, the study strongly advocates for the integration of recycled aggregate in concrete as a means to foster sustainable development and environmentally friendly construction methods. [ABSTRACT FROM AUTHOR]

Addressing environmental challenges such as pollution and resource depletion requires innovative industrial and municipal waste management approaches. Cement production, a significant contributor to greenhouse gas emissions, highlights the need for eco-friendly building materials to combat global warming and promote sustainability. This study evaluates the simultaneous use of Sugarcane Bagasse Ash (SCBA) and Stone Dust (SD) as partial replacements by volume for cement and sand, respectively, at varying ratios in eco-strength concrete mixes designed for 28 MPa (ES-28) and 34 MPa (ES-34), emphasizing their economic and environmental benefits. The influence of SCBA and SD on workability, mechanical properties, and durability were experimentally investigated. Results reveal that for ES-28, with 9% SCBA and 50% SD, compressive and tensile strengths were nearly equal to the control mix, while flexural strength improved by 6.86%. For ES-34, with 9% SCBA and 50% SD, compressive strength was enhanced by 10.16%, tensile strength by 11.68%, and flexural strength by 5.22%, compared to the control mix. This improvement is attributed to pozzolanic reactions, enhanced particle packing, and optimal curing conditions. However, water absorption increased significantly, with ES-28 showing a 31.61% rise and ES-34 a 22.32% rise when SCBA was 9% and SD was 50%. These results highlight the trade-offs between mechanical performance and durability. The optimized mix, derived from response surface analysis, demonstrates significant potential as a sustainable alternative to conventional concrete, aligning with environmental and structural performance objectives. [ABSTRACT FROM AUTHOR]

This study investigates the efficacy of silane-modified zeolite powder in enhancing the early age crack resistance of concrete. Three concrete mixes were evaluated: a reference mix, a 20 % zeolite replacement mix, and a silane-modified zeolite mix. The silane-zeolite mix demonstrated significant improvements, extending the time to crack by 70 % compared to the reference mix (from 11.2 to 19.1 hours). Mechanical strength tests revealed a 58 % increase in first-crack strength for the silane-zeolite mix over the reference mix. Water absorption tests showed that the silane-zeolite mix absorbed 42 % less water than the reference mix, indicating a denser microstructure. Microscopic analyses confirmed these findings, revealing a more refined pore structure with reduced microcrack frequency and width in the silane-zeolite mix. These results highlight the potential of silane-modified zeolite in improving concrete durability and longevity. [ABSTRACT FROM AUTHOR]

The current study investigates the performance of precious slag (PS) ball as 100% fine aggregate in alkali-activated slag–fly ash concrete (AASFC) for concrete pavements. PS ball is an industrial product obtained from the iron and steel industry completely replaced by natural sand. As an activator solution, sodium silicate (SS) and sodium hydroxide (SH) were utilized, with SH concentrations of 8 M, 10 M, and 12 M. Different SS/SH ratios (1, 1.5, and 2) were used to make AASFC combinations with a 0.3 alkaline liquid-to-binder ratio. AASFC mixes properties such as mechanical strength and durability properties were studied. The test result revealed incorporation of PS ball to the AASFC mix helps in the development of strength and has a major impact on workability. The compressive, tensile and flexural strength of the material improved with SH and SS concentration due to the increased viscosity of the activator solution. The AASFC mixes with PS ball reported high fatigue cycle than specified in the case of traditional concrete with less resistance towards abrasion; the same has been validated through Weibull distribution analysis. The durability performance of AASFC mixes will be investigated through sorptivity test, evaluation of permeable voids with an acid attack test. The test result indicates SH and SS have a significant role towards acid resistance and capillary action involved in the AASFC mixes. [ABSTRACT FROM AUTHOR]

In the past few years, one of the most promising graphite-based nanomaterials in the construction industry has been Graphene Oxide (GO) due to its outstanding performance combined with cementitious composites. Introducing extensive Engineering Cementitious Materials (ECMs) improves Ultra-High-Performance Concrete (UHPC) mechanical, durability, and microstructural characteristics. Very few studies have been concentrated on cement pastes, mortars, and regular concrete, high strength concrete. Limited studies on UHPC with large volumes of ECMs done. The present investigation mainly focuses on improving the UHPC in fresh, mechanical, and microstructural behavior. Four mixes were prepared with GO (0.00%, 0.03%, 0.06%, and 0.1% by weight of cement) and a water-cement ratio of 0.20. Results indicated that the mix with 0.06% GO had a better outcome and improved the compressive, split tensile, and flexural strength compared with other test mixes. Microstructural analysis carries out using x-ray fluorescence (XRF), x-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-dispersive x-ray Spectroscopy (EDS), Thermogravimetric Analysis (TGA), Fourier-Transform Infrared Spectroscopy (FTIR), Fourier-Transform Raman Spectroscopy (FT-RAMAN) on 28 days UHPC mixes and quality of the concrete mixes analyzed with Ultrasonic Pulse Velocity (UVP) test. They developed and established the fundamental step toward the cost-effective, eco-friendly, sustainable UHPC. [ABSTRACT FROM AUTHOR]

Utilizing alternate aggregates is crucial for conserving resources, promoting sustainability, and managing waste effectively. The focus of the current study was the utilization of ferrochrome aggregate (FCA) and recycled concrete aggregate (RCA) in cement-treated base layers with the objective of entirely replacing natural coarse aggregate (NCA). The study meticulously prepared cement treated recycled and ferrochrome aggregate (CTRFA) specimens with 3%, 5%, and 7% cement content. These specimens incorporated varying blends of RCA and FCA, ranging from 0% to 100%. Response surface method (RSM) was used to optimize the mixes by considering strength and durability criteria for cement treated bases (CTB). Microstructural characterization was aimed to explore aggregate surface roughness, mortar hardness, mineral phases, cracks, and elements within the matrix. The outcomes of optimization revealed that the optimal mixture, meeting the specifications of the Indian Road Congress, could be achieved by substituting 61% RCA and 39% FCA with 4.8% cement content. [ABSTRACT FROM AUTHOR]

In recent years, research on self-compacting concrete (SCC) has gradually shifted towards high-strength development, while high-strength self-compacting concrete has been widely used in applications such as precast bridge components and high-rise building projects. Using manufactured sand as an aggregate can effectively address the challenges posed by the depletion of natural sand resources. This study optimized the mix design for high-strength self-compacting concrete with manufactured sand (MSH-SCC) and explored the effects of the fine aggregate replacement rate, sand ratio, and maximum particle size of coarse aggregate on the performance of MSH-SCC. The results indicated that the optimized mix designs for various strength levels met the performance requirements. The fine aggregate replacement rate and the maximum nominal aggregate size significantly affected the workability of the concrete, while variations in the sand ratio had a smaller impact. The yield stress of the MSH-SCC showed a positive correlation with the fine aggregate replacement rate and the maximum nominal aggregate size, whereas the plastic viscosity reached its maximum value under specific conditions. Additionally, the mix design parameters had a limited effect on the mechanical strength of the MSH-SCC. This study provides a scientific basis for the design of high-strength self-compacting concrete with manufactured sand, contributing to the promotion of manufactured sand use and advancing low-carbon development in the construction industry. [ABSTRACT FROM AUTHOR]

This article presents the procedure for designing self-compacting cement concrete characterized by minimal free space and a maximally compacted mineral skeleton. Such a designed mix allows for lower cement consumption and an increased amount of mineral additives. The paper presents a broad analysis of the influence of different aggregate proportions (36 recipes) and verification of the properties of the concrete mix using CEM I 42.5 R cements and fly ash. As a result of the appropriately compacted mineral skeleton, only 17% free space was obtained, which will allow the amount of cement to be reduced from 500 kg/m3 to 350 kg/m3 while fully maintaining the properties of the mix and hardened concrete. After 90 days of curing, SCC concrete was characterized by a compressive strength above 68 MPa and a small 2.1% decrease in compressive strength after 100 freeze–thaw cycles. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The use of bacterial concrete has become popular as a way to fix fractures in a variety of constructions, including pavements, pipelines, canal linings, bridges, and reinforced concrete buildings. Concrete constructions frequently have cracks that let water and other chemicals in, weakening the structure and compromising reinforcement. Henk Jonkers came up with the idea of bacterial concrete to solve this issue. Concrete cracks were sealed experimentally using calcium lactate and Bacillus subtilis. The bacteria that were chosen were those that could thrive in alkaline conditions. M20 and M40-grade concrete mixes substituted river sand and crushed stone sand for fine aggregate with varying proportions of B. subtilis and calcium lactate. At various curing ages, the study looked at how bacteria affected abrasion resistance. For various mixtures, empirical relationships were proposed between various concrete properties and bacterial content. [ABSTRACT FROM AUTHOR]

Geopolymer concrete offers a promising alternative to traditional Portland cement concrete, exhibiting comparable mechanical and durability performance while reducing environmental impacts. However, its mechanical and durability properties depend on many factors, such as the water/binder ratios, concentration of activator and curing temperatures. This study proposes using an unsupervised Artificial Neural Network (ANN) Self-Organizing Map (SOM) to predict the factors that control the durability of geopolymer concrete in a chloride environment based on experimental datasets. This research aims to identify the impact of various water-to-binder ratios and molarity of activators on the durability of geopolymer concretes by applying the Growing Self-Organizing Maps (GSOM) model to predict the durability of the design mix. A series of geopolymer concrete mixes with varying water-to-binder (w/b) ratios and activator molarity were prepared to achieve these goals. These cylindrical samples of 100 mm height x 50 mm diameter size were cured for 24 hours at 80°C and subject to chloride migration test at 28-day curing age. The data collected was analyzed and modeled using statistical methods and machine learning techniques, i.e., SOM modeling. This modeling approach effectively revealed patterns and relationships within the dataset, providing crucial insights into the chloride migration behavior. Based on the GSOM modeling, this study highlights efficient data analysis, pattern recognition, and optimization of outcomes, such as geopolymer concrete durability prediction in a chloride environment based on the selected parameters. [ABSTRACT FROM AUTHOR]

Indonesia is among the nations with a comparatively high risk of earthquakes. Concrete is one of the most commonly utilized building materials. By mixing foam liquid, also known as a foam agent, with the water in the concrete design mix, this research can create foam concrete. The goal of this study is to analyze the link between precast foam concrete panels' load and deflection. This research is conducted as a lab experiment. This investigation is being conducted in a laboratory as an experiment. The volumes of foam that this research used were 15.7, 25.12, and 37.68 liters. The 40 x 70 x 8 cm precast foam concrete panels (PFCP) are utilized. The strength of the PFCP is assessed by load and deflection testing with UTM equipment attached to an LVDT. After 28 days, this research test for deflection and load. According to the study's findings, the volume weight that resulted was 1210.71 kg/m³. The PFCP test item produced an average load of 64.64, 61.04, and 26.79 kN for each modification in foam volume, resulting in a deflection of 2.65, 4.16, and 4.22 mm. The results of the study demonstrate that PFCP can be utilized in reinforced concrete frame walls in place of bricks, Hebel, briquette, and other filler materials. Additionally, this research can be applied to non-structural materials like fillers or partitions. The panels have the advantage of not absorbing heat, which can save energy for air conditioning systems, and they require less aggregate and cement due to their reduced density. [ABSTRACT FROM AUTHOR]

This research is part of an effort to advance the use of Buton rock asphalt (EBBRA)--an asphalt emulsion derived from extracted bitumen--as a binder. EBBRA, or extraction bitumen Buton rock asphalt, consists of 70% mineral and 30% asphalt. To produce bitumen emulsion, cationic emulsion, kerosene, hydrochloric acid, calcium chloride, and water are combined with the bitumen extracted from EBBRA. Coarse, fine, and filler aggregates are then mixed with the EBBRA-based asphalt emulsion to create an Asphalt Concrete Wearing Course (AC-WC) mixture. Marshall specimens are used to measure the stability of this EBBRA-containing asphalt emulsion. Test results indicate that bitumen emulsions made with EBBRA deliver asphalt concrete mixes with high stability, satisfactory flow, and a favorable Marshall Quotient (MQ). Moreover, increasing curing time improves stability and reduces flow across all emulsified asphalt mixtures. This study emphasizes the use of environmentally friendly materials, including Buton asphalt and other locally sourced materials from Indonesia. By utilizing Buton asphalt, Indonesia could potentially reduce its reliance on imported petroleum bitumen. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fiber-reinforced concrete (FRC) is a type of concrete with added fibers that has become an interesting material for researchers to study its properties and behavior in a variety of scenarios. Fibers are long, thin, needlelike particles that are mixed into a typical cement paste, mortar, or concrete matrix. Researchers conducted various review studies on the use of fiber in concrete mixes to evaluate the changes in concrete properties. However, they had certain limitations because they only looked at one type of concrete or fiber, or how fiber influenced a restricted number of concrete properties. Others have decided to focus solely on recycled fibers, ignoring the effect of industrial fresh fibers on concrete. This work aims to develop an extensive database containing various types of fibers, fiber properties, fiber ratios, concrete mixtures, and aggregate particle varieties. The purpose of this database is to fill in the gaps and weaknesses of previous review papers and provide a comprehensive and detailed analysis of the literature produced by researchers studying fiber-reinforced concrete. The literature defined the effects of fibers in various kinds of use for different types of concrete. The study examines the impacts of fibers on the fifteen main features of concrete, employing 149 literatures that comprise its durability, workability, and mechanical capabilities. Compressive strength, tensile strength, flexural strength, modules of elasticity, density, toughness, ultrasonic pulse velocity, slump, V funnel, L box, J ring, chloride penetration, air content, and electrical resistance are some of these topics. The results of each property were recorded from the literature and shown in graphs to make a clear comparison for different references which used various mix proportions, mix types, fiber dosages, and types, with aggregate types corresponding to mixture types. The fiber dosages for every literature were recorded in the database and the comparison in the graphs was made according to this fiber dosage. It is important to analysis the behavior of different concretes that contain various fiber types including different aggregates to understand the interaction of all these factors on concrete performance in the form of strength and workability, while looking for long-term behavior and durability. Moreover, understanding the materials behavior is important for leading researchers to further applications in structural concrete. According to the literature, essentially, the best technique to improve compressive strength is to increase the fiber content by up to 1%, and the most common and efficient type of fiber for this purpose is steel fiber. The tensile strength of concrete is greatly enhanced with the addition of fibers, which take the form of a web-like structure resembling a space truss. According to the sources that were examined, concrete's flexural strength may be increased by up to 1.5% by adding more fiber. Flexural strength has enhanced by 50% to 70% or even more in the majority of investigations. The workability of the concrete has been negatively impacted by the fiber addition. Friction between the aggregates and the fibers provides a good explanation for the great majority of data, which are valid for nearly all types of fibers and concrete. Furthermore, this study investigates how fiber affects concrete durability in the presence of chloride penetration and discovers that adding additional fiber minimizes the amount of tensile and compressive strength loss. Most studies predicted increased concrete density, and the findings showed that high-fiber volume fraction combinations included more air than low-fiber volume fraction mixes. [ABSTRACT FROM AUTHOR]

Copyright of Low-Carbon Materials & Green Construction is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The current research focuses on the usage of microbial concrete, which has a considerable impact on its mechanical characteristics. Microbial concrete is not only important, but it also employs environmentally acceptable approaches. The "Megaterium bacteria" of the Bacillus genus are put into concrete to heal fractures by fixing microscopic cracks in the transition zone and to improve the mechanical qualities of the concrete. Bacterial concentrations are altered and combined with the conventional concrete to see how the mechanical characteristics change, and the findings demonstrate that the bacterial concrete has a significant increase in strength. The bacteria produced the best results when combined with cementitious materials at a concentration of 107 cfu/ml, according to the findings. In addition to the aforementioned approach, calcined clay was used to partially substitute cement. Experiments were conducted with the replacement of calcined clay (0%, 10%, 15% & 20%) by mass of Ordinary Portland Cement (OPC) in the concrete mix with different concentrations of bacteria. The current study discovered that cement replacement with 10% calcined clay when mixed with bacteria dosage of 107 has the potential to increase the strength attributes of traditional concrete. It also decreases the porosity of the concrete which additionally results in durable concrete. [ABSTRACT FROM AUTHOR]

AbstractIn this study, several concrete mixes were developed by partially replacing all concrete mix components with recycled expanded polystyrene (EPS) beads. The replacement ratios ranged from 10% to 60% of the total mix volume. The impact of compaction was also studied by casting half of the specimens without compaction and the other half with compaction. Evaluations included thermal conductivity, density, compressive, flexural, and splitting tensile strengths. Results showed that EPS replacement improved thermal insulation but reduced density and all mechanical properties. Density decreased by 8% to 46% for compacted and 14% to 60% for uncompacted specimens. Thermal conductivity dropped by 38% to 74% for compacted and 58% to 85% for uncompacted specimens. The compressive strength of compacted specimens decreased exponentially, but those with up to 40% EPS were suitable for load-bearing blocks. Specimens containing 50% EPS exhibited a compressive strength of 7.2 MPa, making them suitable for non-structural applications requiring good thermal insulation properties. Although the EPS substitution lowered the strength-to-density ratio, it is expected to produce a more eco-friendly LWC due to reduced cement, water, and aggregate consumption. [ABSTRACT FROM AUTHOR]

Splitting tensile strength (fspt) is a crucial parameter in designing concrete mixes. The addition of steel fibers helps improve the mechanical properties of concrete, including its fspt. Due to the complexity and time-consuming processes required in conducting tensile tests, this study proposes a novel integration of differential evolution (DE) and an extreme gradient boosting machine (XGBoost) for estimating the fspt of concrete mixes based on their constituents, age, and compressive strength. XGBoost is used to learn the nonlinear and multivariate mapping function between the fspt and its influencing factors. In addition, DE, as a metaheuritic algorithm, is employed to automatically optimize the XGBoost performance. A dataset, including eight predictor variables and 173 records, is used to train and verify the hybrid DE-XGBoost approach. Experimental results, supported by statistical tests, show that the newly proposed method can achieve outstanding predictive accuracy with a mean absolute percentage error (MAPE) of 9.5% and a coefficient of determination (R2) of 0.9. Sensitivity analysis shows that the contents of aggregates and water critically affect the fspt. Meanwhile, the volume fraction of steel fiber, aspect ratio of steel fibers, binder quantity, and concrete age moderately influence tensile strength performance. Moreover, an asymmetric squared error loss function is used during the training phase of XGBoost to reduce the percentage of overestimated fspt values from 52 to 35% with a minor loss of predictive accuracy. [ABSTRACT FROM AUTHOR]

Addressing the need for sustainable construction materials that minimize environmental impact and reduce CO2 emissions, particularly in OPC compositions. Assessing alccofine and metakaolin in OPC compositions to determine their impact on concrete strength, durability, and microstructure in alkaline environments for sustainable material development. Experimental investigation involved incorporating alccofine and metakaolin into OPC concrete mixes, creating binary and ternary blended systems. Modified concrete specimens were subjected to various alkaline attacks using diluted solutions of magnesium sulfate (MgSO4), sodium sulfate (Na2SO4), and sodium chloride (NaCl) both individually (5%) and in combination (2.5%), resulting in significant improvements in concrete strength and durability. The modified concrete exhibits enhanced resistance to alkaline attacks, reduced weight and compression strength loss, and superior performance in Base Durability Factor (BDF) and Base Attack Factor (BAF) compared to conventional specimens. Scanning electron microscopy (SEM) study of the altered concrete's microstructure shows that it has a densely packed microstructure, which increases its load-bearing capability. Mineral admixtures aid pore clogging, leading to denser, more alkali-resistant concrete due to finer particles. Notably, Alccofine and metakaolin offer effective solutions for sustainable construction materials, aiding in the decrease of CO2 releases during cement production and addressing critical gaps in sustainable material development. [ABSTRACT FROM AUTHOR]

The over usage of natural sand and cement has negative social and ecological effects. To address this, by-products of industrial wastes known as pozzolanic materials, including as fly ash, GGBFS, silica fume, and metakaolin, can be utilised with the manufactured sand in place of the natural fine aggregate and cement. As a result, the current research project discussed in this article examines the viability of replacing cement in concrete with pozzolana and crushed sand. Thus, this will address two issues at once: the large-scale use of pozzolanic materials and the preservation of natural sand quarries. The main objective of this experimental investigation is to find out the impact and durability properties of concrete produced by replacing natural sand by manufactured sand in varying percentages like 0, 10, 20, 30, 40, 50, 60 70, 80, 90, 100, and 20% cement replacing with pozzolanic materials. Cylindrical disc 150 mm diameter and 65 mm thick was tested for impact strength and chloride permeability 50 mm thick and 100 mm diameter samples were cast. The 28-day impact strength and chloride permeability of concrete mixed by partially substituting cement with pozzolan and partially substituting natural fine aggregate with artificial sand were tested. For the various concrete mix proportions, the findings for impact strength and chloride permeability were examined and contrasted with standard concrete. The results of this study show that substituting 20% of the cement with silica fume and 60% of the natural fine aggregate with M-sand results in concrete that has a maximum impact strength and a minimum chloride permeability. An ANN Model was developed using the experimental values. For design of model 400 result values where used, 20% results used for testing purpose and 80% results used for ANN model training. Calculated using the product of 25 input data. The ANN model's results offer a precise elastic prediction of the impact strength and chloride iron pass ability of concrete mixed with substituting industrial cementitious waste for cement and artificial sand with naturally occurring fine aggregate. The findings of this study help to reduce the extraction of non-renewable natural recourses and the environmental impact of industrial waste by preparing more sustainable concrete. [ABSTRACT FROM AUTHOR]

Cement replacement materials are used in self-compacting concrete mixes to reduce the cement content and hence its environmental effect. This article examined the effects of ground granulated blast-furnace slag (S) and natural pozzolan (NP) powder on the rheological and mechanical properties of recycled self-compacting mortar (RSCM). Natural sand was replaced by 100% of recycled sand (RS) by volume; while cement was replaced by slag and NP up to 40% by weight of cement. The slump flow, V-funnel time, yield stress and plastic viscosity and compressive strength of RSCM are investigated and compared with natural self-compacting mortar. The results showed that fresh properties of RSCM meet the requirements of self-compacting mortar if slag and NP contents are limited to 35%. The increase in slag content increases the yield stress and the plastic viscosity of fresh mortars whereas a decrease in the rheological properties is noticed when NP content is increased. Increasing slag and NP content leads to a reduction in compressive strength of RSCM at early ages, but enhances compressive strength at later age. The cement substitution levels by 25% of slag and 15% of NP are the optimum for attaining the desired strength that compensate for strength loss due to the use of RS. [ABSTRACT FROM AUTHOR]

The current paper explores the performance, microstructure and environmental consequences of low-calcium fly ash-based geopolymer concrete compared to OPC-based concrete. The performance of the concrete is assessed based on strength, permeability, sulfate resistance, and acid attack. Two geopolymer mixes were designed by adjusting the binder dosage. The geopolymer concrete mixes achieved 11–16% higher strength than OPC-based concrete. However, increasing the binder dosage from 30 to 40% led to 5% reduction in strength at later ages. Geopolymer concrete demonstrated superior resistance to sulfate and acid attacks, as well as lower penetration depth and permeability coefficient compared to OPC-based concrete. Microstructural analysis was conducted using XRD and SEM techniques, identifying sodium aluminosilicate gel as the product formed during the polymerization process. The environmental impact was evaluated through a life cycle assessment using a cradle-to-gate approach. Geopolymer concrete requires 25–33% less energy and emits 14–28% less kg-CO2 eq. than OPC-based concrete. The production of OPC-based concrete had the greatest negative environmental impact, except in the categories of metal depletion (MDP) and ionizing radiation (IRP_HE). In geopolymer concrete, the use of alkaline activators accounted for higher energy consumption and accounted for 73–75% kg-CO2 eq. emissions. Overall, fly ash-based geopolymer concrete showed higher strength and excellent resistance to acid and sulfate attacks, along with a lower carbon footprint and energy consumption. [ABSTRACT FROM AUTHOR]

Current testing methods for fresh concrete are time-consuming and operator-dependent and, thus, should be replaced with automatic testing methods. This study investigated automated measurement techniques for determining water/cement (w/c) ratio and air content in fresh concrete, addressing this need for more efficient and continuous quality control. The research compared microwave absorption (MWA) and time-domain reflectometry (TDR) techniques for w/c ratio measurement as well as acoustic wave propagation (AWP) technique for air content measurement, against the reference testing methods. Laboratory investigations were conducted on various concrete mix compositions. Results showed that MWA and TDR techniques demonstrated a good correlation with reference methods for w/c ratio (R² = 0.808 and 0.858, respectively), but were sensitive to air content variations. The AWP technique for air content measurement showed a moderate correlation with the pressure method (R² = 0.654 for static measurements), with accuracy influenced by concrete consistency. The study highlights the potential of these automated techniques for real-time concrete quality control, while also revealing limitations related to mix composition variations and calibration requirements. These findings contribute to the ongoing development of more precise and reliable automated measurement systems for fresh concrete properties, supporting the move towards advanced quality control methods. [ABSTRACT FROM AUTHOR]

This study examines the impact of different curing methods on the compressive strength of concrete. It investigates techniques such as air curing, periodic water spraying, full water submersion, and polyethylene encasement. Artificial neural network models were employed to evaluate the compressive strength under each curing condition. A model for calculating compressive strength that considers surrounding conditions was created using an artificial neural network. The current study's figures were generated using this model. The research thoroughly examined the impact of curing environments and concrete mix components on strength properties, taking into account factors such as temperature, the inclusion of additives such as fly ash and silica fume, adjustments in water-to-cement ratio, selection of aggregates, and the integration of various admixtures. One important discovery is that models that predict compressive strength based on 28-day water immersion do not accurately represent the actual strength because of the substantial impact of local curing conditions. Furthermore, concrete that was cured in polyethylene bags exhibited noticeable differences in moisture retention and temperature properties when compared to alternative methods. Understanding and evaluating curing conditions is crucial for accurate strength predictions. The study also found that compressive strength decreases with temperatures above 30°C and below 15°C. [ABSTRACT FROM AUTHOR]

AbstractThis study investigates the bleeding and water permeability characteristics in Foamed Concrete (FC) containing natural zeolite as cement substitute and Cuttle-Bone Powder (CBP) as nano-bio-filler. The aim of this study is to conduct a comparative analysis on pore structure modifications and engineering properties between conventional FC and admixture modified FC. First; four distinct FC mixes were obtained by adding CBP as an additive at 0%, 10%, 20% and 30%. Second; three mixes were produced; by replacing cement with calcinated natural zeolite at 5%, 10% and 15% of the mix containing 5%, 10% and 15% CBP; respectively. The foam volume was varied at 10%, 20%, 30% and 40% by volume of concrete in each mix. The test results indicate that substituting cement with natural zeolite in FC containing CBP affects the microstructural properties. In addition, isolated air void formation and reduced foam breakage was observed which restricts the bleeding, drying shrinkage and permeability. [ABSTRACT FROM AUTHOR]

Changes in the current use of concrete materials and design approaches are mandatory in order to comply with the requirements imposed on future sustainable concrete structures. Before this background, the article indicates the design of sustainable concrete mixes (green concretes or eco-concretes) and the structural components made from them. Such concretes are characterized by a pronouncedly reduced CO2 footprint compared to conventional structural concretes made purely with Ordinary Portland Cement (OPC). After an introduction to the sustainability problems of today's structural concretes, the basic approaches for the development of sustainable concrete are presented. The specific parameter Concrete Sustainability Potential is introduced, which combines the main effecting parameters such as environmental impact, service life (durability) and performance (strength). An overview of possibilities available today for producing sustainable concrete mixtures is given. For good reasons, emphasis is placed on such sustainable concretes, in which a large proportion of the OPC is replaced by rock powders. Finally, a new and innovative relationship for sustainability design is introduced. This concept is equally applicable to concrete as a material and to components made from it. The article concludes with considerations on the implementation of this new concept in practice. [ABSTRACT FROM AUTHOR]

Load absorption of deflection forces – Investigations into the break‐out resistance of concrete reinforcing bars In curved reinforced concrete structures, the steel tensile forces result in radially directed deflection stresses in the concrete, which can cause the concrete cover to spall and the reinforcing bars to pull out. To investigate the absorption of these deflection forces by the concrete, the influence of various parameters on the break‐out forces of reinforcing bars was determined at Münster University of Applied Sciences. The influence of different bar diameters (16, 20, 25, 28 and 32 mm) and the influence of the interaction between several reinforcing bars with different concrete mix designs were investigated. The result of these tests is that larger rebar diameters and a higher concrete quality generally generated higher breaking loads. [ABSTRACT FROM AUTHOR]