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This study presents test results and deep discussion regarding measurements of the fracture toughness of new concrete composites based on ternary blended cements (TCs). A composition of the most commonly used mineral additive (i.e., fly ash (FA)) in combination with nano-silica (NS) has been proposed as a partial replacement of the ordinary Portland cement (OPC) binder. The novelty of this article is related to the fact that ordinary concretes with FA + NS additives are most often used in construction practice, and there is a decided lack of fracture toughness test results concerning these materials. Therefore, in order to fill this gap in the literature, an extensive evaluation of the fracture mechanic parameters of TC was carried out. Four series of concretes were created, one of which was the reference concrete (REF), and the remaining three were TCs. The effect of a constant content of 5% NS and various FA contents, such as 0, 15%, and 25% wt., as a partial replacement of cement was studied. The parameters of the linear and nonlinear fracture mechanics were analyzed in this study (i.e., the critical stress intensity factor ( K I c S ), critical crack tip opening displacement (CTODc), and critical unit work of failure (JIc)). In addition, the main mechanical parameters (i.e., the compressive strength (fcm) and splitting tensile strength (fctm)) were evaluated. Based on the studies, it was found that the addition of 5% NS without FA increased the strength and fracture parameters of the concrete by approximately 20%. On the other hand, supplementing the composition of the binder with 5% NS in combination with the 15% FA additive caused an increase in all mechanical parameters by approximately another 20%. However, an increase in the FA content in the concrete mix of another 10% caused a smaller increase in all analyzed factors (i.e., by approximately 10%) compared with a composite with the addition of the NS modifier only. In addition, from an ecological point of view, by utilizing fine waste FA particles combined with extremely fine particles of NS to produce ordinary concretes, the demand for OPC can be reduced, thereby lowering CO2 emissions. Hence, the findings of this research hold practical importance for the future application of such materials in the development of green concretes. [ABSTRACT FROM AUTHOR]

According to wastewater concrete (WWC) specimens of different sizes (L = 40 mm, L = 100 mm, L = 150 mm, L = 200 mm) and different freeze–thaw cycles (FTCs) (N = 0, N = 10, N = 20, N = 30, N = 40, N = 50), the compressive strength (CS) and splitting tensile strength (STS) of specimens with different sizes under different FTCs were tested. After 50 FTCs, the maximum and minimum loss rates of CS of cube specimens were 60.07% and 24.11%, respectively. The maximum and minimum loss rates of STS were 54.76% and 17.42%, respectively. The relationship between the number of FTCs and the size of the specimen on the CS of concrete was obtained, and the damage model of WWC based on damage mechanics theory with the number of FTCs for different specimen sizes was established. Using the fitting method, the strength model of CS and STS for different specimen sizes under FTCs was established. The R2 is 0.9709 and 0.9627, the fitting performance is good, and the freeze–thaw damage (FTD) models can accurately predict the freeze–thaw damage degree of concrete under the coupling effect of FTCs and specimen sizes. [ABSTRACT FROM AUTHOR]

Abstract To achieve dual optimization of the mechanical properties and environmental impacts of geopolymer concrete (GPC), this study proposes a high-strength geopolymer concrete (HSGPC) without coarse aggregate. The mix proportion of HSGPC was optimized using the response surface methodology, targeting compressive strength and splitting tensile strength to determine the optimal mix. Additionally, the carbon emission impact of HSGPC was assessed and compared with ordinary Portland cement concrete, ultra-high-performance concrete, and reactive powder concrete. The results indicate that the optimal mix proportion for HSGPC includes 15% fly ash content, 10.30% silica fume content, alkali activator ratio of 2.5, and a NaOH molar concentration of 10 M. Simultaneously, the carbon emissions of HSGPC are reduced by about 30% compared to ordinary Portland cement concrete. Compared to ultra-high-performance concrete and reactive powder concrete of the same strength, the production of HSGPC respectively reduces carbon emissions by 59.87% and 68.24%. This study not only provides valuable technical support for the practical application of GPC in engineering but also holds significant implications for promoting sustainable development in the construction industry.

This paper explores the influence of polypropylene fiber on the mechanical properties of recycled concrete and the bonding performance between recycled concrete and steel bars. The results indicate that the compressive strength and splitting tensile strength of concrete decrease with the increase in the replacement rate of recycled aggregate. When the replacement rate of recycled aggregate was 100 %, the compressive strength of concrete decreased by 25.0%, while the splitting tensile strength of concrete decreased by 21.7 %. The compressive strength and splitting tensile strength of recycled aggregate concrete show a trend of first increasing and then decreasing with increasing fiber content. When the fiber content is 0.09 %, the compressive strength and tensile strength of recycled aggregate concrete are optimal. The bond strength of recycled concrete pullout specimens with fiber is higher than that of recycled concrete pullout specimens without fiber, while the slip of recycled concrete pullout specimens with fiber is lower than that of recycled concrete pullout specimens without fiber. The maximum improvement in bonding performance between recycled concrete and rebars with a 50 % recycled aggregate replacement rate is 13.7 %, and the maximum improvement in bonding performance between recycled concrete and rebars with a 100 % recycled aggregate replacement rate is 11.8 %. The bond strength shows a trend of first increasing and then decreasing with increasing fiber content, but the degree of decrease was not significant, while the slip shows a trend of first decreasing and then increasing with increasing fiber content. Compared to the compressive strength of concrete, the splitting tensile strength can better reflect the bond strength between concrete and rebar. The nonlinear relationship between the bond strength, compressive strength, and splitting tensile strength of recycled concrete is established. This study can effectively improve the mechanical properties of recycled concrete, expand the application scope of recycled concrete technology, and promote the sustainable development of the construction industry.

Using recycled fine aggregates from discarded sintered shale bricks as a quality substitute for natural sand to prepare recycled concrete, the study investigated the impact of the substitution rate of recycled fine aggregates from discarded sintered shale bricks on the performance of concrete and conducted microscopic analysis. The results showed that with the increase of the substitution rate of recycled fine aggregates from discarded sintered shale bricks, the compressive strength and splitting tensile strength of recycled concrete showed a downward trend. However, the recycled concrete with a substitution rate of 20% can reach the strength level of ordinary concrete and meet the standard requirements. Microscopic analysis showed that with the increase of the substitution rate of recycled fine aggregates, they blocked the development of hydration products, affected the close connection of crystals in internal space, and had a negative impact on the internal structure of concrete. [ABSTRACT FROM AUTHOR]

Over two centuries, concrete has been crucial to building. Thus, eco-friendly concrete is being developed. Emulating these tangible traits has recently gained popularity. Ceramic waste concrete's mechanical properties were modeled in this study. Ceramic waste percentages ranged from 5 to 20%. Compressive and tensile concrete strengths were modeled. To predict concrete hardness, regression modeling and artificial neural network (ANN) were used. Model performance was evaluated using prediction coefficients and root-mean-square error (RMSE). ANN models outperformed linear prediction with a coefficient for determination (R2) of 0.97. ANN models achieved root-mean-square errors (RMSEs) of 1.22 MPa, 1.21 MPa, and 1.022 MPa after 7, 14, and 28 days of retraining, respectively. Linear regression model showed RMSE values of 1.21, 1.32, and 1.27 MPa at 7, 14, and 28 days, respectively. In determining the compressive and tensile strength, the R2 was 0.70, meanwhile the ANN model achieved 0.87. Given its accuracy in predicting the strength qualities of ceramics cement and structural stiffness, the ANN model presents a promising tool for representing various types of concrete. [ABSTRACT FROM AUTHOR]

To study the influence of interface angle on the tensile properties of rock-concrete composite specimens, Brazilian splitting tests of rock-concrete composite specimens under different loading angles were carried out by using the RMT-150B rock mechanics test system. The angle between the rock-concrete interface and the loading direction is 0°–90°. It is found that the tensile strength of rock-concrete composite specimens is greater than that of rock, and increases first and then decreases with the increase of loading angle. When the loading angle is 45°, the tensile strength reaches the maximum. The average splitting energy rate increases first and then decreases with the increase of loading angle and changes synchronously with the average tensile strength. Because the rock-concrete is bonded by grooves, the shear strength of the interface is large, and the specimen only exhibits tensile failure along the loading direction. By measuring the macroscopic crack length of the sample, it is found that the crack length decreases first and then increases with the increase of the loading angle. Finally, based on the plane stress problem in elastic mechanics, the stress analysis of the rock-concrete interface is carried out. [ABSTRACT FROM AUTHOR]

High performance concrete (HPC) has the characteristics of high strength, high brittleness and low toughness, so it can not be widely used in engineering field. The rubber particles themselves have good elasticity and excellent wear resistance. To this end, rubber particles were used to prepare high performance rubber concrete (HPRC) instead of fine aggregate, and compressive strength and splitting tensile strength tests were carried out according to standard test methods. These data were evaluated, and it was found that adding different mesh number (10 mesh, 20 mesh, 30 mesh) and different content (10%, 20%, 30%) of rubber particles reduced the compressive and tensile properties of highperformance rubber concrete to different degrees. The rubber particles with l size of 30 mesh and content of 10% have the least influence on the mechanical properties of high-performance rubber concrete, and the compressive strength and tensile strength of HPC 28 days only decrease by 18.19% and 5.56%, respectively. From the damage form, the addition of rubber particles makes the high performance concrete change from brittle to ductile. The research shows that recycling rubber from waste tires into concrete manufacturing is an environmentally friendly and feasible waste management strategy. These results have the potential to replace concrete in construction and promote sustainable growth. [ABSTRACT FROM AUTHOR]

To study the influences of fire extinguishing agents on the mechanical performance of concretes after high temperatures, specimens of different curing ages were heated to different temperatures at 5 °C/ min and 10 °C / min heating rates, and then they were maintained at different constant temperatures of 200 °C, 400 °C, 600 °C and 800 °C for one hour. The mass loss rate of specimens of different curing ages and heating temperatures were tested. Specimens were moved into a tempered glass frame. Water, Halon 1211, CO2 and HFC-227ea were used to treat these specimens. The results showed that the mass loss rates of the specimen with 7 d and 14 d curing age were significantly higher than that in 28 d curing age at 400 °C . Fire extinguishing agents did not affect the compressive strength of the specimens at room temperature. Water, Halon 1211, and HFC-227ea could reduce compressive strength of the specimens after high temperature treatment at 400 °C and 600 °C . However, water cooling treatment at 600 °C could increase the compressive strength of the specimen with 7 d and 14 d curing age by 9.14% and 9. 18%. Curing age did not affect the experimental results of Halon 1211 and HFC-227ea, and the compressive strength of the specimen was relatively low at 800 °C, which could not reflect the influence of different treatment methods on the compressive strength. Water, Halon 1211, and HFC-227ea fire extinguishing agents could reduce the splitting tensile strength of concrete at 400 °C. CO2 had no influence on the compressive strength and splitting tensile strength of concrete. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to investigate the impact of the thermal processing of natural fibers on the strength of what is considered fiber-reinforced concrete. Natural fibers extracted from palm trees and bamboo residues were collected and pyrolyzed. The investigation of the morphological alterations that occur during the pyrolysis of natural fibers at a temperature of 200°C showed the impact of the cementitious environment on this process. In addition, the mechanical characteristics of fiber-reinforced concrete were conducted on different dosages (1, 1.5, 2, and 5% wt.) of treated and untreated palm oil, date kernel, and bamboo fibers. The results demonstrated that the inclusion of fibers up to 1.5% wt. enhanced the concrete mixes mechanical properties, which included pyrolyzed fibers. Analyzes of the concrete microstructure revealed that the treated fibers were not damaged. The 1.5% wt. addition of fibers after pyrolysis process can effectively improve their adhesion to the matrix and reduce the width and number of cracks. The analysis of variance results for flexural strength indicated that all sources had no significant impact on the flexural strength of untreated or pyrolysis treated natural fiber reinforced concrete.

To promote solid waste reutilization and reduce natural river sand consumption, iron ore tailings (IOT) are expected to be used in concrete production as a potential substitute for river sand under the premise of comparable material properties with ordinary concrete. In this study an IOT concrete reinforced by Polyvinyl Alcohol (PVA) fiber has been proposed and the slump and splitting behavior under various IOT substitution rates and PVA fiber contents has been experimentally investigated. Slump tests reveal that the optimal PVA fiber content is 0.1 % and IOT substitution rate is 60 % from the view of workability. Splitting tensile tests show a monotonous strength growth with PVA fiber content increase. The incorporation of IOT has increased concrete splitting tensile strength but the strength is smaller than that of normal concrete as soon as IOT substitution rates exceed 50 %. A regression model and Back Propagation (BP) neural network model have been adopted to establish splitting tensile strength prediction model. Compared to regression model, the BP model has exhibited better accuracy which is suitable to predict the splitting tensile strength of PVA-IOT concrete with PVA content less than 0.3 %.

Adding fibers into cement to form fiber-reinforced soil cement material can effectively enhance its physical and mechanical properties. In order to investigate the effect of fiber type and dosage on the strength of fiber-reinforced soil cement, polypropylene fibers (PPFs), polyvinyl alcohol fibers (PVAFs), and glass fibers (GFs) were blended according to the mass fraction of the mixture of cement and dry soil (0.5%, 1%, 1.5%, and 2%). Unconfined compressive strength tests, split tensile strength tests, scanning electron microscopy (SEM) tests, and mercury intrusion porosimetry (MIP) pore structure analysis tests were conducted. The results indicated that the unconfined compressive strength of the three types of fiber-reinforced soil cement peaked at a fiber dosage of 0.5%, registering 26.72 MPa, 27.49 MPa, and 27.67 MPa, respectively. The split tensile strength of all three fiber-reinforced soil cement variants reached their maximum at a 1.5% fiber dosage, recording 2.29 MPa, 2.34 MPa, and 2.27 MPa, respectively. The predominant pore sizes in all three fiber-reinforced soil cement specimens ranged from 10 nm to 100 nm. Furthermore, analysis from the perspective of energy evolution revealed that a moderate fiber dosage can minimize energy loss. This paper demonstrates that the unconfined compressive strength test, split tensile strength test, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) pore structure analysis offer theoretical underpinnings for the utilization of fiber-reinforced soil cement in helical pile core stiffening and broader engineering applications. [ABSTRACT FROM AUTHOR]

This comprehensive study analyzes the use of crushed glass as both fine and coarse aggregate in concrete, as well as the prediction accuracy of Artificial Neural Networks (ANN). The primary objectives are to understand the interactions between concrete’s constituents and to assess the accuracy of ANN models in predicting concrete’s mechanical and physical properties. This is achieved using a two-decade experimental results dataset of concrete’s compressive and tensile strengths, slump, density, and the corresponding mix design proportions, including waste glass aggregate. A series of 70 concrete samples were carefully built and tested, with compressive strengths varying from 12 to 71 MPa and glass aggregate percentages ranging from 0-100%. These samples served as the basis for the creation of an input dataset and ANN targets. The ANN model underwent intensive training, validation, testing, and statistical regression analysis. The ANN models are exceptionally accurate, with a continuously low error margin of roughly 2%, highlighting their usefulness in matching experimental and predicted results. Validation techniques highlight the models' dependability, with consistently high coefficients of determination (R-values), including 0.99484, demonstrating their robustness in replicating complicated concrete properties. The data analysis shows a unique pattern, with optimum glass aggregate percentages in the range of 10–20%. Beyond this range, there is a noticeable decline in concrete properties. Finally, the study confirms the efficacy of ANN in predictive modeling while also validating the potential of crushed glass to replace natural aggregates in concrete. [ABSTRACT FROM AUTHOR]

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Cement mortar without fibers might crack due to shrinkage or volume changes. Cracking in cement mortar leads to elastic deformation. The development of these cracks causes elastic deformation of cement mortar. This study examined the influence of two steel fibers' geometrical forms (crimped and hooked with just one end) in different amounts by volume (Volume fraction = 0.25%, 0.5%, and 0.75%) on the cement mortar's mechanical features. Among the characteristics were splitting, compressive as well as flexural strength. The samples were prepared, poured into cubic molds for compressive strength testing cylindrical molds used for splitting strength testing, and prismatic molds for flexural strength testing, and processed at various times 3, 14, and 28 days before the tests. According to the findings, the highest increase was obtained after adding 0.75% of crimped fibers, the compressive strength increased by 13.3 %21.29%, and 44.8%, for 3,14.28 days respectively, and split tensile strength increased by 66.17%,68.9%, and 79.48% for 3.14 and 28 days respectively and flexural strength increased by 72 %,91% and 92% for 3.14 and 28 days, respectively. [ABSTRACT FROM AUTHOR]

As the global population has continued to grow, the costs and environmental issues associated with traditional construction materials like cement and river sand have become increasingly problematic. This research aimed to explore an alternative and ecofriendly approach to traditional building materials. The researchers conducted an experimental program to assess the mechanical properties of the rice husk ash-based concrete at different curing ages 7, 14, 21, and 28 days. Following the mix design, the concrete was produced using water to binder ratio of 0.5. A series of experiments were conducted on both fresh and hardened states to investigate the impact of quarry dust on rice husk ash-based concrete. It was observed from the experimental results that when 40% of the quarry dust was used as a replacement for fine aggregates, the concrete exhibited the highest strength. After 28 days of curing, the compressive strength showed a 0.65% improvement, while the splitting tensile strength displayed a 1.77% enhancement compared to the reference mix. To ensure the reliability of the experimental findings, a statistical analysis was conducted. The study concluded that certain factors, such as quarry dust, curing duration, and rice husk ash, interacted synergistically to influence the compressive and splitting tensile strengths of the concrete. The researchers also proposed equations to predict these strengths based on the aforementioned parameters. [ABSTRACT FROM AUTHOR]

Influence of section depth on the flexural tensile strength of ultra‐high performance concrete Besides axial tensile strength, Eurocode 2 (EC2) defines a so‐called flexural tensile strength. The flexural tensile strength depends on the concrete tensile strength, the section depth of the member, and the brittleness of concrete. When calculating stresses and deflections under service loads, uncracked cross‐sections may be assumed acc. to EC2 if the flexural tensile stress does not exceed the flexural tensile strength. So far, a calculation method for determining the flexural tensile strength does not exist for ultra‐high performance concrete (UHPC). Therefore, in this work, the flexural tensile strength, the axial tensile strength, the splitting tensile strength, and the compressive strength of fine‐ and coarse‐grained UHPC without fibres are determined and related to each other also considering data from other studies. It turns out that coarse‐grained UHPC tends to show lower tensile strength than fine‐grained UHPC with comparable compressive strength. For specimens treated with heat or stored in dry climatic condition, internal stresses reduce the effective tensile strength to a greater extent when the section depth increases. By storing the test specimens in water, internal stresses can be prevented. An approach is proposed for calculating the flexural tensile strength of both fine‐ and coarse‐grained UHPC, which assumes a linear dependence on the section depth. The results are intended to be considered with the DAfStb Guideline "Ultra‐high Performance Concrete". [ABSTRACT FROM AUTHOR]

This study evaluated the feasibility of using polypropylene fiber (PF) as reinforcement in improving tensile strength behavior of cement-stabilized dredged sediment (CDS). The effects of cement content, water content, PF content and length on the tensile strength and stress–strain behavioral evolutions were evaluated by conducting splitting tensile strength tests. Furthermore, the micro-mechanisms characterizing the tensile strength behavior inside PF-reinforced CDS (CPFDS) were clarified via analyzing macro failure and microstructure images. The results indicate that the highest tensile strengths of 7, 28, 60, and 90 d CPFDS were reached at PF contents of 0.6%, 1.0%, 1.0%, and 1.0%, exhibiting values 5.96%, 65.16%, 34.10%, and 35.83% higher than those of CDS, respectively. Short, 3 mm, PF of showed the best reinforcement efficiency. The CPFDS exhibited obvious tensile strain-hardening characteristic, and also had better ductility than CDS. The mix factor (CCa/Cwb) and time parameter (qt0(t)) of CDS, and the reinforcement index (kt-PF) of CPFDS were used to establish the tensile strength prediction models of CDS and CPFDS, considering multiple factors. The PF "bridge effect" and associated cementation-reinforcement coupling actions inside CPFDS were mainly responsible for tensile strength behavior improvement. The key findings contribute to the use of CPFDS as recycled engineering soils. [ABSTRACT FROM AUTHOR]

The development of very effective coarse aggregate types and sizes can lead to a rapid increase in the production of high strengthconcrete (HSC). This research investigates the effects of five different coarse aggregate types and a range of maximum coarse aggregate sizes on the mechanical properties of concrete through experimental tests and numerical analysis. The workability of fresh concrete is examined using the slump cone test, whereas the mechanical performance of hardened concrete is assessed through compressive strength and splitting tensile strength tests. The experimental results are compared to the predicted results from the codes and design guidelines to assess their predictions. Both coarse aggregate types and sizes show a significant influence on the mechanical properties of HSC performance, especially the compressive strength of HSC, which could be increased on average by 25%. Moreover, the predictions of splitting tensile strength using the ACI 318 and ACI 363 equations are not very accurate, particularly at a high strength range. Therefore, this study develops a new equation for predicting splitting tensile strength based on both experimental test results conducted in this research and a significant amount of data collected from the literature. Evaluation metrics, including R2, RMSE, MAPE, and MAE, demonstrate the superior accuracy of the proposed equation compared to the design guidelines equations. The findings of this research can contribute toward the optimization of aggregate type and size in concrete mix design for enhanced performance and provide valuable insights into the relationship between compressive and splitting tensile strengths in HSC.

Nanotechnology has made significant inroads across various sectors, augmenting properties and economic impacts. Its pivotal role extends notably to the realm of construction and building. This study focuses on the tangible consequences of incorporating nano-silica (NS) into lightweight concrete (LWC) and its influence on mechanical attributes. The primary aim is to illustrate how NS impacts the mechanical properties of LWC, specifically its effects on compressive strength, flexural strength, and tensile strength in comparison to conventional LWC. The research encompassed the casting and examination of seven distinct concrete mixtures, including a reference mix, in laboratory settings. The study findings highlight that the utilization of lightweight Iraqi porcelanite stone resulted in a one-third reduction in the weight of standard concrete. Furthermore, the introduction of varying quantities of NS into structural LWC yielded enhancements in compressive, tensile, and flexural strength when contrasted with the reference mix, albeit at the expense of workability. Remarkably, The results showed an introduction of varying quantities of NS into structural LWC yielded enhancements in compressive, tensile, and flexural strength when contrasted with the reference mix, albeit at the expense of workability. The findings demonstrated that when doses of 1, 3, 5, 10, 15, and 20% NS were applied, the rate of three models for determining compressive strength at 90 days old rose by 19, 45, 62, 32, 15, and 37%, respectively. On the other hand, when dosages 1, 3, 5, 10, 15, and 20% were added, the percentage of improvement in tensile strength at 28 days of age was 77, 75, 84, 51, 55, and 53%. Additionally, while employing the same above doses, the bending strength at 28 days of age improved by 141, 140, 171, 115, 114, and 108%, respectively. Remarkably, the results also underscored the sustained efficacy of NS, particularly during the later stages of concrete maturation.

Incorporating steel fibers into concrete effectively enhances its tensile strength by managing crack formation, increasing toughness and ductility, and reducing brittleness, making it a valuable choice for various applications, including bridge decks. Thus, the objective of this research is to employ the machine learning (ML) technique to estimate the splitting tensile strength (STS) of steel fiber-reinforced concrete (SFRC) that incorporates hooked industrial steel fibers (ISF) using SFRC mixtures collected from various research papers in this field. The dataset comprises 116 data points from various research papers. Utilizing the recursive feature elimination with cross-validation and leave-one-out (RFECV-LOO) method, the most influential parameters, including ISF content, water-to-cement ratio (W/C), cement content (C), fine aggregate content (FA), superplasticizer (SP), and fly ash, were identified to train the ML models. Eight statistical metrics, including the root mean squared error (RMSE), mean squared error (MSE), mean absolute error (MAE), coefficient of determination (R2), mean absolute percentage error (MAPE), mean bias error (MBE), statistical test (Tstat), and scatter index (SI) were employed as metrics to assess model performance. Various ML models including multiple linear regression (MLR), ridge regression (Ridge), lasso regression (Lasso), elastic net regression (ElasticNet), k-nearest neighbor (KNN), support vector regression (SVR), categorical boosting (CatBoost), light gradient boosting model (LightGBM), random forest (RF), gradient boosting (GB), extreme gradient boosting (XGB), adaptive boosting (AdaBoost), and multilayer perceptron (MLP) were employed to predict the SFRC’s STS. The Python programming language, TensorFlow framework as well as the Scikit-learn packages, were used to run the models. Among the various ML methods, SVR demonstrated higher accuracy, achieving an R2 of 0.930, RMSE of 0.502, and MAE of 0.330. In contrast, linear regression models, especially Lasso with an R2 of 0.631, RMSE of 0.854, and MAE of 0.710, exhibited the least effective performance when it came to predicting the STS of SFRC. Moreover, the performance of the developed ML models was approved through sensitivity analysis as well as parametric analysis.

Due to the brittle nature of ceramic, the ceramic and construction industry produces a large volume of waste that imposes a severe environmental threat due to its non-biodegradability. In this study, the suitability of ceramic waste as a replacement of natural coarse and fine aggregate in concrete has been investigated by evaluating engineering properties such as bulk density, water absorption, workability, etc. with respect to different concrete samples made with different mix proportions. Furthermore, a prediction model is introduced to predict compressive and splitting tensile strength using the machine learning tool support vector machine (SVM). A data set containing 108 records either for compressive or tensile strength was used for the training and testing purposes of the SVM model. A total of 9 mix proportions was selected and cast cylinders were cured for 7, 28, and 56 days. Four different kernel functions were used to optimize the results and different accuracy parameters like the value of R2, mean absolute error, mean square error, root mean square error, etc. were compared to find the best kernel function for this study. By primarily evaluating the coefficient of determination (R2), SVM showed an acceptable result with an accuracy of over 90%. Moreover, in terms of other accuracy measurement parameters result indicates that the SVM is an effective tool to predict the compressive and splitting tensile strength of concrete comprised of different proportions of ceramic content.

In order to study the Brazilian splitting characteristics of the frozen stone mixture under the coupling effect of freezing temperature and size effect, Brazilian splitting experiments were conducted on 5-10, 10-15, 15-20, and 5-20 mm particle size frozen soil-rock mixture samples after freezing at −10, −15, −20, −25, −30, −35, and −40 ℃ to investigate the effects of freezing temperature and different particle sizes on the splitting tensile strength of the samples. The effects of freezing temperature and different particle sizes on the splitting tensile strength of the samples were investigated, and the strain field evolution of the frozen soil-rock mixture during the Brazilian splitting experiments was further reproduced by digital imagine correlation (DIC). The experimental results show that the tensile strain is concentrated in the sample center with initial crack produced and the splitting damage pattern of the samples is curved and folded, and the larger the particle size is, the more curved the crack is; frozen soil-rock mixture goes through the linear elastic deformation stage when it breaks, and goes through the plastic-brittle damage stage with the increase of tensile stress and the decrease of freezing temperature; the splitting tensile strength has strong temperature sensitivity and increases approximately linearly with the decrease of freezing temperature; the size effect leads to the variability of sample strength, and the splitting tensile strengths are in the order of 5-10, 5-20, 10-15, and 15-20 mm particle size samples.

According to wastewater concrete (WWC) specimens of different sizes (L = 40 mm, L = 100 mm, L = 150 mm, L = 200 mm) and different freeze–thaw cycles (FTCs) (N = 0, N = 10, N = 20, N = 30, N = 40, N = 50), the compressive strength (CS) and splitting tensile strength (STS) of specimens with different sizes under different FTCs were tested. After 50 FTCs, the maximum and minimum loss rates of CS of cube specimens were 60.07% and 24.11%, respectively. The maximum and minimum loss rates of STS were 54.76% and 17.42%, respectively. The relationship between the number of FTCs and the size of the specimen on the CS of concrete was obtained, and the damage model of WWC based on damage mechanics theory with the number of FTCs for different specimen sizes was established. Using the fitting method, the strength model of CS and STS for different specimen sizes under FTCs was established. The R2 is 0.9709 and 0.9627, the fitting performance is good, and the freeze–thaw damage (FTD) models can accurately predict the freeze–thaw damage degree of concrete under the coupling effect of FTCs and specimen sizes.

Cement production in the world market is steadily increasing. In 2000, it was 1600 million tons, while as of 2013, the annual amount exceeded 4000 million tons. The burning of cement clinker is associated with the generation of waste. It is estimated that the amount of cement kiln dust (CKD), during combustion, reaches about 15–20%, which means 700 million tons per year. However, not all types of by-products are reusable due to high alkali, sulfate, and chloride contents, which can adversely affect the environment. One environmentally friendly solution may be to use CKD in the production of high-performance concrete (HPC), as a substitute for some of the cement. This paper presents a study of the short- and long-term physical and mechanical properties of HPC with 5%, 10%, 15%, and 20% CKD additives. The experiments determined density, water absorption, porosity, splitting tensile strength, compressive strength, modulus of elasticity, ultrasonic pulse velocity, and evaluated the microstructure of the concrete. The addition of CKD up to 10% caused an increase in the 28- and 730-day compressive strengths, while the values decreased slightly when CKD concentration increased to 20%. Splitting tensile strength decreased proportionally with 5–20% amounts of CKD regardless of HPC age. Porosity, absorbability, and ultrasonic pulse velocity decreased with increasing cement dust, while the bulk density increased for HPC with CKD. Microstructure analyses showed a decrease in the content of calcium silicate hydrate (C–S–H), acceleration of setting, and formation of wider microcracks with an increase in CKD. From the results, it was shown that a 15% percentage addition of CKD can effectively replace cement in the production of HPC and contribute to reducing the amount of by-product from the burning of cement clinker. [ABSTRACT FROM AUTHOR]

Due to the brittle nature of ceramic, the ceramic and construction industry produces a large volume of waste that imposes a severe environmental threat due to its non-biodegradability. In this study, the suitability of ceramic waste as a replacement of natural coarse and fine aggregate in concrete has been investigated by evaluating engineering properties such as bulk density, water absorption, workability, etc. with respect to different concrete samples made with different mix proportions. Furthermore, a prediction model is introduced to predict compressive and splitting tensile strength using the machine learning tool support vector machine (SVM). A data set containing 108 records either for compressive or tensile strength was used for the training and testing purposes of the SVM model. A total of 9 mix proportions was selected and cast cylinders were cured for 7, 28, and 56 days. Four different kernel functions were used to optimize the results and different accuracy parameters like the value of R2, mean absolute error, mean square error, root mean square error, etc. were compared to find the best kernel function for this study. By primarily evaluating the coefficient of determination (R2), SVM showed an acceptable result with an accuracy of over 90%. Moreover, in terms of other accuracy measurement parameters result indicates that the SVM is an effective tool to predict the compressive and splitting tensile strength of concrete comprised of different proportions of ceramic content. [ABSTRACT FROM AUTHOR]

Water losses in canals is a very common issue and have many sources among these sources the major source is seepage, Compared to other forms of water losses, seepage accounts for 20-30% from the canal. and to reduce this water loss concrete is being used from a very long time. Even in cement-concrete conventional sections still (15-20%) has been observed. The major cause of seepage is cracks in the canals sections and performance of the canals gets affected by the increase in the rate of cracking in concrete canal-lining. The cracking rate can be controlled by improving the flexure, compressive and splitting tensile strengths of concrete. From these, splitting-tensile strength of concrete plays a vital role in controlling cracks. The ancient way of improving the concrete characteristics is using different type of fibres, the natural fibres has many benefits, like flexibility, there availability, least health hazards and their low cost etc. in this study the author aimed to explore materials for better performance of canal-lining in terms of reduced water losses by controlling its rate of cracking due to alternate wetting and drying, and due to differential settlement, etc. The purpose of this work was to examine experimental behaviours of fibres reinforced concrete using different fibres. [ABSTRACT FROM AUTHOR]

In Pakistan, there is a critical need for exceptional efforts to be taken in developing environmentally friendly concrete through the utilization of waste materials. This will reduce Global warming and protect the natural ecology. This study examines the effect of Silica Fume (SF) as partial substitution of cement on indigenous volcanic ash concrete's mechanical and durability properties. The research includes the fixed percentage of Indigenous Volcanic Ash replacement i.e. 10% and varying percentages of Silica Fume replacements (0%, 2.5%, 5%, 7.5%, and 10%) to assess their impact on concrete's mechanical and durability properties. The experimental program consists of conducting workability, compressive strength, flexural strength, and water absorption tests on concrete specimens. The mechanical and durability properties of concrete specimens were evaluated and compared to those of the control specimens without IVA and SF. The analysis of results reveals that the Concrete Mix IVA10-SF7.5 shows better results for both mechanical and durability properties among other concrete mixes, so this percentage of silica fume and indigenous volcanic ash can be used as a partial replacement of ordinary Portland cement. The outcome contribute to the broader understanding of sustainable and durable concrete production using locally available IVA along with SF resources. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office 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 Revista Ingeniería e Investigación is the property of Universidad Nacional de Colombia, Facultad de Ingenieraia 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.)

Concrete is the most widely used construction material in the world. It is now possible to construct structures out of concrete because this durable compound that consists of water, aggregate, and Portland cement not only gives us many scopes of design but also has a very high compressive strength at a low cost. This paper deals with alternative materials for the most common construction material, cement-based concrete and polymer concrete (PC), containing waste tin fibres. The study covers the fabrication of polymer concrete and the execution of three tests: compressive strength, flexural tensile, and splitting tensile. Tests were conducted to determine the mechanical properties of the PC, and the results were analysed and evaluated on several PC specimens with different ratios of waste tin fibre. The results showed that using waste tin as fibre reinforcement in PC would substantially enhance the overall mechanical performance. Specifically, the optimum amount of waste tin as reinforcement in PC was 0.16% for compressive and splitting tensile strengths, while 0.20% was the optimum fibre loading for the flexural tensile strength. In this case, a positive outcome was found at a constant resin-to-filler ratio of 40:60 by volume and a matrix-to-aggregate ratio of 1:1.35 by weight. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office 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.)

This study investigated the effects of various water types in concrete mixes to minimize freshwater consumption and combat scarcity. River water, sea water, estuary water, domestic wastewater, and fresh water were assessed, analyzing concrete properties such as water absorption, compressive, flexural, and splitting tensile strengths. Results indicated comparable failure modes across different water types in compression, flexure, and splitting. Estuary water decreased compressive strength by 8%, while other water types enhanced it, with domestic wastewater showing the most improvement. Splitting tensile strength saw no significant reductions; domestic wastewater exhibited the highest enhancement (24.39%), followed by estuary and river water, whereas estuary water led in flexural strength improvement. Domestic wastewater reduced absorption and increased slump by up to 60%. To summarize, domestic wastewater positively influenced compressive and splitting tensile strengths, decreased water absorption, and increased slump. River water exhibited properties akin to fresh water, implying its suitability; further exploration into reinforced concrete using these water sources is suggested. [ABSTRACT FROM AUTHOR]

Cement mortar without fibers might crack due to shrinkage or volume changes. Cracking in cement mortar leads to elastic deformation. The development of these cracks causes elastic deformation of cement mortar. This study examined the influence of two steel fibers' geometrical forms (crimped and hooked with just one end) in different amounts by volume (Volume fraction = 0.25%, 0.5%, and 0.75%) on the cement mortar's mechanical features. Among the characteristics were splitting, compressive as well as flexural strength. The samples were prepared, poured into cubic molds for compressive strength testing cylindrical molds used for splitting strength testing, and prismatic molds for flexural strength testing, and processed at various times 3, 14, and 28 days before the tests. According to the findings, the highest increase was obtained after adding 0.75% of crimped fibers, the compressive strength increased by 13.3 %21.29%, and 44.8%, for 3,14.28 days respectively, and split tensile strength increased by 66.17%,68.9%, and 79.48% for 3.14 and 28 days respectively and flexural strength increased by 72 %,91% and 92% for 3.14 and 28 days, respectively.

Various studies on the effect of specimen size on splitting tensile strength. However, geotechnical codes lack consensus regarding the recommended specimen diameter and height-to-diameter (H/D) ratio for the split tensile strength test. Hence, it is imperative to study the effect of the height-to-diameter ratio of the specimen on the outcomes of the split tensile strength test, especially for stabilized and fiber-reinforced soil. This research examines the effect of adding lime-rice husk ash and plastic fiber and the effect of specimen size on splitting tensile strength. The height of the specimen is varied, using a height-to-diameter ratio (H/D), namely 0.5, 1.0, 1.5, 2.0, and 2.5, in which the diameter is 70 mm. Two groups of specimens were prepared as stabilized clay without fibers and stabilized clay with 0.1% fibers. The lime required for stabilization is 10% of the dry weight of the soil. In this research, the lime and rice husk ash ratio was designed as 1:1. The splitting tensile strength test was carried out after the specimen was cured for seven days. The investigation indicates that the splitting tensile strength of the specimen without fibers reduces from 217 kPa to 150 kPa as the H/D ratio grows from 0.5 to 2.5. Conversely, the tensile strength of the specimen with fibers increases from 284 kPa to 357 kPa. The findings suggest that the fiber inclusion enhances the splitting tensile strength of the stabilized clay. The specimen size affects the splitting tensile strength, but the effect becomes less noticeable when the H/D ratio exceeds 2.5. From a fracture mechanism perspective, the specimen experiences mode II (shearing) due to a probable “flexural action” along its height. It remains challenging to conclude the dimensions of the test specimen or, at the very least, estimate the correction factor for the size-to-tensile strength ratio.

The HPFRCC is defined by a stress-strain response in tension, which demonstrates multiple cracking and strain-hardening behavior. This experimental study aims to investigate the splitting tensile strength (STS), compressive strength (CS), and bulk density (BD) of HPFRCC. The CS of concrete should provide an accurate basis for the STS prediction. This study consists of two phases; in the first phase, 18 HPFRCC mix proportions with 1% steel fibers (30 mm length) were formulated by taking into account the various types of aggregate distribution, water-to-cement (w/c) ratio, amount of superplasticizer, and silica fume. After testing 108 cylinder and cube specimens at 7 and 28 days, a mathematical exponential function between STS and CS was proposed with a prediction error of less than ±15%. In the second phase, in order to evaluate the effect of steel fiber volume fraction and age on the prediction equation, three distinct volume fractions of steel fibers were considered: 0%, 1%, and 2%. At the ages of 7, 28, 56, and 90 days, 144 cube and cylinder specimens were tasted. The proposed equation for HPFRCC with 1% steel fiber can be applied to specimens containing 2% fiber with an error of ±20%. Adding fibers to the cementitious mortar had a small effect on the CS. However, at 28 days, the STS for HPFRCC with 1% and 2% fibers increased by 54% and 95%, respectively, compared to specimens without fibers.

This study presents test results and deep discussion regarding measurements of the fracture toughness of new concrete composites based on ternary blended cements (TCs). A composition of the most commonly used mineral additive (i.e., fly ash (FA)) in combination with nano-silica (NS) has been proposed as a partial replacement of the ordinary Portland cement (OPC) binder. The novelty of this article is related to the fact that ordinary concretes with FA + NS additives are most often used in construction practice, and there is a decided lack of fracture toughness test results concerning these materials. Therefore, in order to fill this gap in the literature, an extensive evaluation of the fracture mechanic parameters of TC was carried out. Four series of concretes were created, one of which was the reference concrete (REF), and the remaining three were TCs. The effect of a constant content of 5% NS and various FA contents, such as 0, 15%, and 25% wt., as a partial replacement of cement was studied. The parameters of the linear and nonlinear fracture mechanics were analyzed in this study (i.e., the critical stress intensity factor (KIcS), critical crack tip opening displacement (CTODc), and critical unit work of failure (JIc)). In addition, the main mechanical parameters (i.e., the compressive strength (fcm) and splitting tensile strength (fctm)) were evaluated. Based on the studies, it was found that the addition of 5% NS without FA increased the strength and fracture parameters of the concrete by approximately 20%. On the other hand, supplementing the composition of the binder with 5% NS in combination with the 15% FA additive caused an increase in all mechanical parameters by approximately another 20%. However, an increase in the FA content in the concrete mix of another 10% caused a smaller increase in all analyzed factors (i.e., by approximately 10%) compared with a composite with the addition of the NS modifier only. In addition, from an ecological point of view, by utilizing fine waste FA particles combined with extremely fine particles of NS to produce ordinary concretes, the demand for OPC can be reduced, thereby lowering CO2 emissions. Hence, the findings of this research hold practical importance for the future application of such materials in the development of green concretes.

Bu çalışmada yüksek dayanımlı betonların erken yaş yarmada çekme dayanım sonuçlarının kapsamlı değerlendirilmesi sunulmaktadır. Bunun için çimento ile hacimce %5, %10 ve 15 oranlarında silis dumanı ve ince agrega ile hacimce %8, %10 ve %12 oranlarında mermer tozu yer değiştirilerek 72 seri beton karışımı hazırlanmıştır. Hazırlanan bu karışımlarda Su/Çimento (S/C) oranları 0.20-0.25-0.30 ve çimento dozajı ise 400-450-500 kg/m3 olarak seçilmiştir. Elde edilen numunelere 3. ve 7. günlerde yarmada çekme dayanımı testi uygulanmıştır. Bu testler sonucunda alınan veriler tepki yüzeyi metodu (TYM) kullanılarak analiz edilmiştir. Analiz sonucunda yarmada çekme dayanımını tahmin eden matematiksel modeller geliştirilmiştir. Geliştirilen matematiksel modellerin doğruluğunun tespiti için 9 adet kontrol serisi hazırlanmış ve modelin tahmin sonuçları ile karşılaştırılmıştır. Bunun sonucunda bağıl hata oranları (BHO) hesaplanarak geliştirilen matematiksel model doğrulanmıştır.

This paper compares the performance of natural molasses (NM) and superplasticizer (SP) on the properties of cement mortar. The base mortar with a w/c ratio of 0.50 and a unit water content of 220 kg/m3 was used in this experimental work. The different percentages of NM and SP (by weight of cement) were used to assess the physical and mechanical properties of the cement mortar. Test results showed that NM was a better retarder, milder plasticizer, and has stronger viscosity-enhancing capacity than SP. The optimum content of NM was 87% less than SP. A similar compressive strength was obtained with the optimum content of NM and SP. However, the splitting tensile strength with NM was more than that with SP. NM helps to reduce the cement. It produces cheaper green concrete to support the development of sustainable infrastructures. The effect of NM on durability properties is yet to be studied.