Search

The aim of this study is to evaluate the potential use of wood ash as a cement additive. Four wood specimens from Yaoundé city of (Cameroon) were used namely: Sapelli, Iroko, Movingui and Padouk. Five mortar were produced, with cement substitutions of 0%, 5%, 10%, 15% and 20%. The fresh rheological, mechanical and hardened durability properties of various mortar were obtained after 7, 14, 28 and 56 days. The results showed that cement paste consistency and the cuing time increases with the addition of ash. At 28 days, the mortars obtained from the 5% and 15% Padouk and Movingui ash substitutes, respectively, showed optimum compressive strength (9%, 6%) and flexural strength (5%, 3%) compared with the control mortar. Due to continuous pozzolanic activity, this flexural gain is multiplied by 3 for Movingui mortar (9%) at 56 days. Compared with the 28-day and 56-day compressive strength results, there were increases of 5% and 4% respectively for the 5% and 15% ash substitutions in Padouk and Movingui mortars. Durability results were evaluated through absorption, which showed relatively identical rates in mortars containing ash from Padouk and Movingui wood, due to their water content for normal consistency. Chemical attack with H2SO2 and NaCl proved that the incorporation of ash improved the mortars' resistance to chemical attack. Thermal analyses and microscopic observations were performed with the optimum. [ABSTRACT FROM AUTHOR]

This study investigated the effect of rubber content on the mechanical characteristics of ultra-high-performance rubberised concrete (UHPRuC). The results revealed a distinctive non-linear decrease in the dry density of UHPRuC as the rubber content increased. Notably, lower rubber content led to a columnar failure mode, while higher content (≥ 20%) exhibited a mixed failure mode with vertical cracking and diagonal fracture. Importantly, the compressive strength showed minimal reduction compared to conventional concrete, presenting a remarkable 50% mitigation of strength reduction compared to previous studies. Utilising reference concrete with robust bond strength proved highly effective in preserving strength in rubberized concrete. Despite its effectiveness in mitigating compressive strength reduction, UHPC could not effectively offset flexural strength loss, which ranged from 1.5 to 3 times that of compressive strength loss. The addition of rubber aggregate in UHPC reduced the peak flexural strength, residual strength, and flexural toughness at a similar rate, while significantly increasing the vibration decaying rate. Incorporating 40% rubber in UHPRuC reduced the eCO2 up to 37%. Our findings emphasise the importance of reference concrete with good bond strength and shows that the addition of rubber aggregate in UHPC leads to reductions in strength but increases the energy-dissipating capacity. [ABSTRACT FROM AUTHOR]

The longevity of waste asphalt can be considerably improved through cold recycling techniques combined with various additives. This research investigates the cold regeneration of aged asphalt concrete using Reclaimed Asphalt Pavement (RAP), Portland cement, cationic bitumen emulsion, and additional aggregates. The primary goal is to evaluate the performance enhancements in terms of average density, compressive strength, water resistance, and swelling across different mix compositions. Three distinct mixtures were formulated and assessed. Mix No. 1, composed solely of RAP, showed the lowest average density and highest swelling, indicating poor performance due to the lack of binding agents. Mix No. 2, which incorporated RAP, Portland cement, and water, exhibited the highest density and compressive strength, highlighting the crucial role of Portland cement in improving structural integrity. Mix No. 3, a more complex mixture including RAP, aggregates, Portland cement, water, and bitumen emulsion, displayed balanced properties with enhanced moisture resistance and reduced swelling. The experimental findings emphasize the effectiveness of adding Portland cement and bitumen emulsion to improve the mechanical and durability characteristics of recycled asphalt mixtures. Specifically, Mix No. 2 and Mix No. 3 demonstrated significant performance improvements, making them suitable for road maintenance applications. This study advocates for the widespread use of cold recycling methods with additive integration to achieve sustainable and cost-effective pavement restoration solutions. [ABSTRACT FROM AUTHOR]

This study aimed to address the critical issue of age deterioration in prestressed concrete (PSC) structures by investigating the strengthening of aged PSC structures using a near-surface mounted (NSM) post-tensioned carbon fiber-reinforced polymer (CFRP). A total of nine PSC beams, each with a length of 6.5 m, were fabricated for a four-point bending test. Various experimental parameters were taken into account, including the strengthening method, compressive strength of concrete in the PSC beam, and the prestressing force of the PSC beam. The results indicated that the NSM post-tensioned CFRP strengthening system proved more efficient when compared to the NSM non-post-tensioned CFRP strengthening system. The flexural capacity of the NSM post-tensioned CFRP strengthening system, under the deteriorated low-strength PSC beam, increased by up to 30.9% compared to the PSC reference beam. Additionally, the experimental results were compared to a finite-element analysis, and a parametric study was conducted to examine the material properties of the PSC beam. Consequently, the NSM post-tensioned CFRP strengthening system is expected to be an effective solution for addressing the issue of deteriorated low-strength PSC structures. [ABSTRACT FROM AUTHOR]

The magnetite ore was taken as the partial aggregate to prepare two types of concrete specimens mixed with magnetite and without magnetite. Both were cured in water and 5 wt % Na2SO4 solution at 20 and 80°C, respectively, to study the influence on the strength of concrete. In addition, the magnetite ore was ground into powder, and cured in simulated concrete pore solution and 5 wt % Na2SO4 solution respectively, and the mineral and morphological change at different ages was tested by X-ray diffraction (XRD) and scanning electron microscope/energy dispersive spectrometer (SEM/EDS). The experimental results show that the strength of concrete with magnetite ore is a little higher than that of concrete without magnetite ore whether cured in water or in Na2SO4 solution, and the magnetite transforms into Fe2O3, ferrihydrite and other minerals in simulated concrete pore solution and in 5 wt % Na2SO4 solution. The experimental results also demonstrate that using some magnetite ore as aggregate for concrete is beneficial for improving the sulfate resistance of concrete. [ABSTRACT FROM AUTHOR]

The main objective of this research is to investigate experimentally the effect of crushed and uncrushed coarse aggregate on the properties of hardened concrete (compressive strength) by adopting the American Concrete Institute (ACI) and the British Department of Environment (DoE) methods. Concrete mixes were designed, concrete cubes and cylinders were prepared and casted by using DoE and ACI respectively. DoE concrete design method considers both types of aggregates; crushed and uncrushed, while the ACI method does not take into account the effect of uncrushed coarse aggregate in design provisions. Then compressive strength tests of concrete samples were determined at ages of 7 and 28 days full curing period. The results obtained show that ACI gave higher values of compressive strength than that obtained by DoE for M30 and M40 except M25, which resulted in lower values than that obtained by DoE for crushed coarse aggregates. The 7-day compressive strength represents 75% of the 28-day compressive strength for ACI method, whereas in DoE reaching up to 73% and 77% for crushed and uncrushed coarse aggregate, respectively. [ABSTRACT FROM AUTHOR]

Compressive strength of grouted concrete masonry is an important parameter to design reinforced/grouted concrete masonry walls. The design standards stipulate two methods to determine the compressive strength of masonry (1) using tabulated unit strength and mortar type, and (2) testing representative masonry prisms. The compressive strength prediction of grouted concrete masonry is influenced by compressive strength values of hollow blocks, mortar and grout, and their geometries. Therefore, a multi-level approach was employed in this study to improve the existing unit strength correlations of the standards for more reliable prediction of compressive strengths of grouted concrete masonry. The existing methods to determine the compressive strength of grouted masonry were critically appraised and a database of compression tests of grouted concrete masonry prisms/wallettes was developed. This database was then used to evaluate the correlations between the compressive strengths of block, mortar, grout and masonry. The applicability of existing unit strength correlations from the design standards and literature were assessed and their relevancy and limitations are highlighted. Subsequently, updated sets of unit strength correlations are proposed in this study, through statistical reliability analyses of the predictions against the experimental results included in the database. The proposed unit strength correlations were classified according to the mortar type/strengths (≤ 10 MPa and > 10 MPa). It has been shown that the new correlations are more structurally reliable than the existing unit strength correlations through comparing the 95th percentile error values. [ABSTRACT FROM AUTHOR]

Purpose: Alkali activation process has been applied to fresh river clay-rich sediments in order to increase their mechanical properties and make them suitable for soil stabilization. Materials and methods: Dredged sediments were mixed with up to 30 mass percent (ma%) of fly ash (FA) or ladle slag (LS) and after curing for 3 days at 60 °C, the bending and compressive strength have been determined. The mixtures which exhibited the highest strengths were further optimized for being used in soil stabilization. For this purpose, the sediment was stabilized with 4 ma% of quicklime (QL) and after 1 h 30 ma% of FA with alkali activator was added and cured for 1, 7 and 28 days. Results: The stabilized sediment has a significantely better geomechanical performance in comparison with the sediment alone. Stabilizing the dredged sediment using alkali activation technology provides high enough strengths to eventually make it suitable for anti-flood embankments. Conclusions: The results confirmed the suitability of the investigated technology for soil stabilization. [ABSTRACT FROM AUTHOR]

This study has focused on reducing the carbon emissions and energy consumption for producing ferrochrome, an essential component in stainless-steel manufacturing. The research primarily investigates the reduction behavior and compressive strength of chromite pellets in atmospheres based on methane and hydrogen. The findings indicate that the reduction of pellets is positively influenced by temperature, time, and methane proportion. The most favorable reduction conditions were established with a methane concentration of 10% and a hydrogen concentration of 90% at 1100°C for a duration of 3 h, which achieved a comprehensive metallization rate of 36.3% for the pellets, with a strength of 1051 N. Additionally, the study has revealed that, with the decomposition of spinel, various chromium carbides initially formed, followed by the production of metallic chromium due to the highly reactive carbon released from methane cracking. The carbon filled the voids in the pellets, leading to densification of the surface layer. However, an excess of carbon can result in the pellets' outer layer becoming fragile and disintegrating. Therefore, the amount of methane input has been identified as a crucial factor affecting pellet strength, highlighting the need for a balanced methane input to effectively optimize pellet consolidation. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA) is widely used in the treatment of bone defects due to its good properties, but the problem of its slow degradation rate needs to be solved urgently. In this study, different proportions of Mg were introduced into PLA to promote and regulate its degradation. A three-dimensional porous composite bone scaffold made of PLA and Mg was prepared using selective laser sintering (SLS). Degradation results showed that the weight loss rate of the Mg-containing scaffold within 4 weeks was nearly five times higher than that of the pure PLA scaffold. Moreover, the degradation mechanism was further explored, and it was believed that the addition of Mg could consume the acidic degradation products of PLA, thus destroying the integrity of the PLA molecular chain and accelerating the flow of the molecular chain, ultimately forming a cycle that promotes degradation. In addition, the magnesium-containing scaffold (PLA/3Mg) also showed good compressive strength (5.6 MPa), which was nearly twice as high as that of the pure PLA scaffold (2.67 MPa). Therefore, we believe that introducing an appropriate amount of Mg can better adjust the balance between the degradation and mechanical properties of PLA scaffolds. [ABSTRACT FROM AUTHOR]

The traditional methods for enhancing the bearing capacity of loess foundations are limited by high resource consumption and environmental pollution. In contrast, microwave and resistance wire thermal reinforcement has emerged as a more efficient and environmentally responsible alternative. However, existing research on the strength characteristics and micro-mechanisms of microwave and resistance wire thermal reinforcement in wet and soft loess is still limited. To address this gap, this study conducted indoor direct shear tests and undrained compressive strength tests on thermally reinforced loess using strength theory. This research examined the variations in strength characteristics under different heating conditions. The study found that with increasing heating temperature, thermally reinforced loess experienced the following changes: 1) an increase in peak shear stress accompanied by a decrease in shear displacement; 2) an improvement in shear strength; and 3) a transition from plasticity to brittleness in failure characteristics under peak pressure, accompanied by an increase in undrained compressive strength. [ABSTRACT FROM AUTHOR]

This study focuses on the essential task of monitoring the strength of structural concrete in construction and rehabilitation projects. The conventional non-destructive testing (NDT) approach offers an indirect estimation of concrete compressive strength. However, the existing models lack the ability to address the estimation of compressive strength in concrete mixtures containing bottom ash (BA) and recycled coarse aggregate (RCA). This study aims to bridge this gap by accurately estimating the compressive strength of such concrete using the ultrasonic pulse velocity (UPV) technique. To achieve this objective, various concrete specimens with different cement content, water–cement ratios (w/c), recycled coarse aggregate, and bottom ash contents through weight batching, were prepared. UPV and compressive strength measurements were taken on cylindrical concrete specimens after 28 and 90 days of curing. The analysis revealed an exponential relationship between the compressive strength and UPV, with a high correlation coefficient across the evaluated concrete mixes, independent of the curing time. Ultimately, two robust models were developed to predict the compressive strength of concrete mixes containing different percentages of RCA and BA, respectively, at 28 and 90 days of curing. These models offer valuable insights and practical tools for ensuring the structural integrity of concrete in construction and rehabilitation projects involving bottom ash and recycled coarse aggregate. [ABSTRACT FROM AUTHOR]

Bioactive glasses containing boron oxide have attracted substantial attention owing to their unique attributes and the promising prospects they offer for biomedical uses. The study explores boro calcium fluoro alumino silicate (BCFAS) glass containing boron oxide, highlighting its potential in biomedical applications. The glass was synthesized through melt-water quenching with varying B2O3 ratios, utilizing CaO from clam shell and SiO2 from soda lime silica glass waste. The investigation examined the physical and mechanical properties of the resulting samples. Results showed that increasing B2O3 content caused a reduction in crystallinity, as confirmed by XRD analysis. The incorporation of B2O3 into the glass structure was further supported by the emergence of B‒O‒B and Si‒O‒B bonds observed in FTIR spectroscopy, which may potentially influence the glass's dissolution and degradation characteristics. However, higher B2O3 content also reduced density, impacting the mechanical properties. Vickers microhardness and compressive strength decreased due to the introduction of the BO3 unit, which increased the fragility of the glass. While enhancing glass-like behavior and potentially increasing bioactivity, the addition of B2O3 adversely affected its mechanical attributes. [ABSTRACT FROM AUTHOR]

The compressive strength of concrete depends on various factors. Since these parameters can be in a relatively wide range, it is difficult for predicting the behavior of concrete. Therefore, to solve this problem, an advanced modeling is needed. The aim of the literature is to achieve an ideal and flexible solution for predicting the behavior of concrete. Therefore, it is necessary to develop new approaches. Artificial Neural Networks (ANNs) have evolved from a theoretical method to a widely utilized technology by successful applications for a variety of issues. Actually, ANNs are a strong computing tool that provides the right solutions to problems that are difficult to use conventional methods. Inspired by the biological neural system, these networks are now widely used for solving a wide range of complicated problems in civil engineering. This study"s target is evaluating the performance of developed African vulture optimization algorithm (DAVOA)-Elman neural networks (ENNs) by considering different input parameters in predicting the self-compacting concrete compressive strength. Hence, once 8 parameters and again to get as close as possible to the prediction conditions in the laboratory, 140 parameters entered to the improved version of Elman Neural Networks as input. According to the results, the element network has the lowest mean squares of the test error in predicting the compressive strength of 7 and 28 days in 100 repetitions. Further, in predicting both compressive strengths, the element grid with the Logsig-Purelin interlayer transfer function has the lowest test error, which determines the optimal transfer function. Moreover, the results showed that DAVOA as a reliable tool with time and cost savings have high power in predicting the desired characteristics. Also, in predicting both 7-day and 28-day compressive strength, networks built with 140 parameters have a 74.54 and 70.44% improvement in test error over 8-parameter networks, respectively, which directly affects this effect. Further parameters are considered as input to the network error rate in predicting the desired properties. [ABSTRACT FROM AUTHOR]

Amidst the global pursuit of sustainable alternatives in concrete production, this study explores the viability of incorporating by-products or waste materials as aggregates to support the concrete construction industry, with a specific emphasis on steel slag. The objective of this study is to evaluate the effectiveness of steel slag as a partial replacement for fine and coarse aggregates in concrete production. The experiment involved casting 30 cubes and 10 beams, replacing fine aggregate from 0 to 60%. Flexural and compressive strength tests at 7 and 28 days followed the ACI method. Results revealed that a 30% replacement of fine aggregate with steel slag led to higher compressive strength at both 7 and 28 days, while a 45% replacement showed superior flexural strength at 28 days. Further chemical analysis and optimization are recommended for deeper insights. The study concludes with marginal improvements in compressive and flexural strength with steel slag partial replacement, identifying 30% for fine aggregate and 45% for coarse aggregate as optimal replacements. In addition, the mineral composition of steel slag exhibits significant variability, with compounds, including silicon dioxide (SiO2), iron oxide (Fe2O3), manganese oxide (MnO), aluminum oxide (Al2O3), and calcium oxide (CaO). Chemical analysis indicates high silicate content and minimal alkali content, contributing to enhanced strength during concreting. Higher steel slag replacement reduces workability, confirmed by slump tests. However, all mixes maintain a true slump, and unit weight increases with steel slag aggregate replacement. Compressive strength improves incrementally with higher steel slag content, echoing prior research. In addition, flexural strength rises with steel slag replacing both coarse and fine aggregates, suggesting enhanced performance in reinforced concrete structures. These findings highlight steel slag's potential as a sustainable alternative in concrete production, aiming to advance its application in the construction industry, promoting environmental sustainability and economic viability. [ABSTRACT FROM AUTHOR]

Self-compacting concrete (SCC) is an innovative material for construction that offers excellent workability and flowability while achieving effective and uniform compaction without the need for external vibration. Using an experimental approach, this study investigates the effect of incorporating arecanut fibers on the performance of self-compacting concrete (SCC). The focus is on optimizing the fiber content for improved concrete characteristics. The study examines three different fiber lengths (8 mm, 10 mm, and 12 mm) and three volume fractions (1%, 2%, and 3%) while partially replacing 30% of the cement by weight with fly ash. Tests on the workability of the SCC mixes revealed favorable characteristics: slump flow between 650 and 750 mm, T500 slump flow time of 2–5 s, V-funnel time of 5–10 s, L-box ratio of 0.8–1.0, and J-ring values within 0–10 mm as recommended by EFNARC guidelines. Furthermore, incorporating 30% fly ash and arecanut fibers significantly enhanced the hardened properties of the SCC, particularly its compressive strength. A concrete mix containing 2% of 10-mm long arecanut fibers achieved a compressive strength of 40.26 MPa, which is about 15.14% increase compared to the reference strength of 35 MPa. Similarly, using a 1% volume fraction of 12 mm arecanut fibers increased the split tensile strength by 14.04% and the flexural strength by 35.87% compared to the control mix. Fly ash and arecanut fibers enhance the durability of SCC by reducing Coulomb charges and improving resistance to chloride penetration. However, the increased water absorption rate of the fibers can lead to increased overall water absorption in the concrete. Microstructural analysis (SEM) revealed improved bonding and reduced voids, further supporting enhanced durability. Additionally, EDX analysis confirmed the presence of various elements from cement and fly ash, providing valuable data for evaluating the long-term performance of these SCC mixes. [ABSTRACT FROM AUTHOR]

To address the environmental issues arising from the growing scarcity of natural fine aggregates (NFA) and landfilling of waste glass, research is being conducted globally to utilize waste glass as a sustainable fine aggregate. However, contradictory results have been obtained regarding the effect of the type of waste glass and the physical properties of waste glass fine aggregate (GFA) on concrete, making it challenging to promote the use of GFA in concrete. Therefore, to promote the use of GFA in concrete, it is necessary to examine it under field conditions, such as mass-production processes or real-scale concrete applications. This study introduced a mass-production process for GFA, and the effect of mass-produced GFA on mortar was evaluated. The fine aggregate properties (particle aspect ratio, crushing rate, and solubility) of the GFA and the effects of color, content, and particle size on the mortar properties (compressive strength, flexural strength, and ASR expansion behavior) were analyzed, along with the results reported in previous studies. Consequently, the high aspect ratio and microcracks in the particles of mass-produced GFA led to an increase in the strength reduction and ASR expansion of the mortar. These effects appear to be particularly severe for transparent GFA. Overall, this study proposed the content of GFA within 20% or the replacement of fine particles (< 500 μm) in NFA as a condition for sustainable fine aggregate. [ABSTRACT FROM AUTHOR]

In this study, concrete specimens were fabricated based on domestically manufactured materials, and long-term exposure tests were conducted in a domestic coastal environment. This study analyzes the long-term compressive strength characteristics of concrete mixed with admixtures. The mixed materials used were divided into blast furnace slag and fly ash. The blast furnace slag and fly ash were, respectively, produced by replacing ~ 30% and ~ 15% of the cement. The compressive strength was measured at 28 day, 1 year, and 10 years of age and compared with that of ordinary concrete. In addition, the long-term compressive strength results obtained in this study were compared with those of concrete mixed with admixtures reported in the literature. The strengths of the ordinary specimen at 1 year and 10 years of age increased by ~ 10 MPa and ~ 22 MPa compared with those at 28 day of age. However, concrete mixed with admixtures yielded compressive strength increases of ~ 5 MPa and ~ 26 MPa at 1 year and 10 years of age, respectively, compared with those at 28 day of age. A comparison of the compressive strengths of concrete mixed with admixtures reported in the literature (based on age) and those obtained in this study showed that there was an initial strength difference in the range of 10–25%. However, the compressive strength at 10 years of age was almost similar to those reported in the literature with differences of less than 5%. These findings confirmed that when using pozzolanic admixtures, the development rate of the initial strength may vary owing to various factors; however, the long-term strength converges within a certain range. [ABSTRACT FROM AUTHOR]

The surrounding rock of tunnels in cold regions are susceptible to the freeze–thaw cycle resulting from the combination of low temperatures and moisture during tunnel service. The phenomenon will not only lead to the expansion of pores and fissures in the surrounding rock of the initial tunnel, but also destroy the integrity of the rock. This destruction will have a serious impact on tunnel structure and rail transit operation safety. At present, the commonly used thermal insulation measures have some problems such as maintenance difficulties, low economic efficiency, and safety hazards. Therefore, it is urgent to develop a kind of tunnel maintenance grouting material with insulation and anti-permeability, which has the characteristics of simple operation, easy preparation and application. We independently developed a composite grouting material composed of polyurethane (PU), epoxy resin (E-51) and acrylic powder (PMMA). Through the material combustion test, magnesium hydroxide was selected as the flame retardant additive. Moreover, we measured the thermal conductivity, water absorption, apparent density, porosity and strength characteristic parameters. The thermal insulation and anti-permeability characteristics of the composites were also analyzed. The results indicated that the thermal conductivity of the new composite grouting material is 6.3% lower than the PU before adding flame retardant. Compared with the PU with flame retardant, the water absorption decreased by 74.4% and the ultimate strength increased by 33.3%. For the area with an average temperature lower than − 10 °C, we recommend the ratio scheme of E-51: 3%; PMMA: 15%. For the area with high water content in the surrounding rock of the tunnel, we recommend the ratio scheme of E-51: 15%; PMMA: 3%. This study provides new ideas for material preparation and tunnel insulation methods for anti-freezing measures in tunnels during their operational period in cold regions. [ABSTRACT FROM AUTHOR]

Concrete compressive strength testing is crucial for construction quality control. The traditional methods are both time-consuming and labor-intensive, while machine learning has been proven effective in predicting the compressive strength of concrete. However, current machine learning-based algorithms lack a thorough comparison among various models, and researchers have yet to identify the optimal predictor for concrete compressive strength. In this study, we developed 12 distinct machine learning-based regressors to conduct a thorough comparison and to identify the optimal model. To study the correlation between compressive strength and various factors, we conducted a comprehensive analysis and selected blast furnace slag, superplasticizer, age, cement, and water as the optimized factor subset. Based on this foundation, grid search and fivefold cross-validation were employed to establish the hyperparameters for each model. The results indicate that the Deepforest-based model demonstrates superior performance compared to the 12 models. For a more comprehensive evaluation of the model's performance, we compared its performance with state-of-the-art models using the same independent testing dataset. The results demonstrate that our model achieving the highest performance (R2 of 0.91), indicating its accurate prediction capability for concrete compressive strength. [ABSTRACT FROM AUTHOR]

Improper waste management is causing global environmental problems. Waste glass may have adverse impacts on the ecosystem. While a substantial amount of soda-lime glass bottle (SGB) undergoes recycling to create new glass items, a significant volume still ends up in landfills. Therefore, the aim of this study was to explore the potential use of SGB in foamed concrete (FC) production as an aggregate replacement. SGB was substituted for sand in different weight fractions, ranging from 5 to 50%. The fresh state, mechanical, thermal, pore structure, and transport properties were examined. The findings showed a significant enhancement in the FC's mechanical properties when SGB replaced 20% of sand. The compressive, flexural, and splitting tensile strengths exhibited a rise of up to 17.7, 39.4, and 43.8%, respectively. The findings also demonstrated that the addition of SGB improved the thermal conductivity, sorptivity, water absorption, and porosity. The scanning electron microscopy analysis indicated that the inclusion of 20% SGB caused a substantial decrease in void diameter and enhanced its uniformity. A comparison was made between the experimental data and predictions of the mechanical properties using various models of international standards, such as IS 456, ACI 318, NZS-3101, EC-02, AS 3600, and CEB-FIB, along with several references in the literature. The findings implied a strong correlation between the strength properties. The outcomes of this research offer valuable insights into both the possible advantages and constraints of using SGB in FC. Furthermore, this extensive laboratory investigation may serve as a guideline for future study and aid in the advancement of greener and more environmentally friendly FC alternatives. [ABSTRACT FROM AUTHOR]

Rock material, such as sandstone, frequently shows a wide range of fracture characteristics and mechanical responses due to variations in weathering grades and the existence of natural fractures. These natural fractures in sandstone are regularly cemented by different minerals or cementation removed by weathering and/or stained with iron, which can affect the stress-induced fracture pattern and rock strength. These effects, along with fracture orientation and location on mechanical behavior and failure modes resulting from quasi-static loading, are poorly understood. The focus of this paper is to assess the effects of cemented and stained natural fractures on stress-induced sandstone failure mechanism and mechanical behavior, with a focus on natural fracture angle and location. To investigate sandstone mechanical behavior and failure mechanism, six unconfined compressive tests were conducted on specimens with pre-existing natural fractures at different angles (∅) to estimate unconfined compressive strength (UCS) and failure modes. ANSYS was also utilized for finite-element modeling and simulation to analyze comprehensive 3D fractured models. The results revealed that UCS of sandstone decreased with increasing fracture angles of 0°, 20°, 30°, 45°, 50°, to 60°, respectively. Sandstone with a 90° fracture angle exhibits higher UCS than samples with a 0° fracture angle. The findings indicated that sandstone with 0° and 20° fracture angles had multiple fracturing, while specimens with 90° fracture angles provided axial splitting. On the other hand, the shear failure in sandstone specimens occurred as the fracture angle superseded 50°. The simulation results demonstrate that fracture location affects only the UCS of sandstone. [ABSTRACT FROM AUTHOR]

Super absorbent polymer (SAP) has a capacity to enhance the characteristics of cementitious composites in both their fresh and hardened forms. However, it is essential to recognize that the strength of SAP concrete may decrease. By altering the concrete composition and selecting the appropriate type of SAP, it is possible to reduce this reduction. This work employs machine learning (ML) to tackle the issue of strength degradation. The analysis considers ten distinct variables linked to concrete composition and the type of SAP. The study uses machine learning approaches that involve both regression and classification tasks. The use of ensemble learning greatly improves the quality and accuracy of the results, showing its superiority in combining several models to produce more precise predictions. The findings demonstrate that the Support Vector Machines (SVM) and Extreme Gradient Boosting (XGBoost) regression algorithms accurately forecasted the percentage of reduction in strength in SAP concrete. These predictions were based on the concrete composition and SAP details, resulting in R2 values of 0.90 and 0.88, respectively. Furthermore, XGBoost exhibited the highest accuracy, reaching 0.94, when compared to the various categorization algorithms. According to the results, the mean squared error (MSE) of the ensemble model demonstrated superior outcomes. Furthermore, the SHapley Additive exPlanations (SHAP) reveal that some variables, including SAP%, SAP size, and compressive strength, have a significant influence on the strength reduction model. This study aims to bridge the gap between academic research and practical application by developing a web application that employs ensemble learning to precisely forecast the reduction in compressive strength caused by the usage of SAP. [ABSTRACT FROM AUTHOR]

To improve the heat extraction efficiency from the wellbore fluids to the stratum in the geothermal well, thermal insulation cement, which contains of waste glass powder as a heat-insulating material, is proposed to apply in geothermal well's middle and upper sections in the paper. Effect of such glass powers on mechanic and thermal property of thermal insulation cement was then investigated. Various tests were carried out to measure compressive strength, thermal conductivity, microstructure porosity etc. parameters of the thermal insulation cement. Results showed that the waste glass powder would enhance its the compressive strength and improve its the thermal insulation performance. Correlation study between contents of the added waste glass powder in geothermal cements and its mechanic and thermal property was conducted. It was found that thermal insulation cement exhibited its optimum performance when the added content of glass powers was 20% in weight. Analysis of the microstructure porosity with SEM found that the pores in thermal insulation cement with added waste glass powders were mostly closed, tiny and even, and therefore contributed to the compressive strength of the thermal insulation cement; such pores would be also beneficial to improving its thermal insulation performance. [ABSTRACT FROM AUTHOR]

Bentonite plastic concrete (BPC) is extensively used in the construction of water-tight structures like cut-off walls in dams, etc., because it offers high plasticity, improved workability, and homogeneity. Also, bentonite is added to concrete mixes for the adsorption of toxic metals. The modified design of BPC, as compared to normal concrete, requires a reliable tool to predict its strength. Thus, this study presents a novel attempt at the application of two innovative evolutionary techniques known as multi-expression programming (MEP) and gene expression programming (GEP) and a boosting-based algorithm known as AdaBoost to predict the 28-day compressive strength () of BPC based on its mixture composition. The MEP and GEP algorithms expressed their outputs in the form of an empirical equation, while AdaBoost failed to do so. The algorithms were trained using a dataset of 246 points gathered from published literature having six important input factors for predicting. The developed models were subject to error evaluation, and the results revealed that all algorithms satisfied the suggested criteria and had a correlation coefficient (R) greater than 0.9 for both the training and testing phases. However, AdaBoost surpassed both MEP and GEP in terms of accuracy and demonstrated a lower testing RMSE of 1.66 compared to 2.02 for MEP and 2.38 for GEP. Similarly, the objective function value for AdaBoost was 0.10 compared to 0.176 for GEP and 0.16 for MEP, which indicated the overall good performance of AdaBoost compared to the two evolutionary techniques. Also, Shapley additive analysis was done on the AdaBoost model to gain further insights into the prediction process, which revealed that cement, coarse aggregate, and fine aggregate are the most important factors in predicting the strength of BPC. Moreover, an interactive graphical user interface (GUI) has been developed to be practically utilized in the civil engineering industry for prediction of BPC strength. [ABSTRACT FROM AUTHOR]

In this study, Al2219 composites with varying wt.% of Si3N4 particles using a combination of stir casting and squeeze casting techniques have been explored. Al2219 alloy with 3, 6, and 9 wt.% of Si3N4 composites was examined for the microstructures through SEM analysis, which revealed an even dissemination of the reinforcement particles within the base matrix. Remarkably, did not observe any issues such as particle agglomeration, residual porosity, or other casting-related problems. The inclusion of ceramic particles in the squeezed composites led to significant increments in hardness, tensile and yield strength, and Izod impact strength when compared to the base Al2219 matrix alloy. Notably, during compression testing, observed a considerable increase in compressive strengths, albeit at the expense of reduced failure strain, as the concentration of hard ceramic reinforcement particles increased. [ABSTRACT FROM AUTHOR]

To solve the supporting problem of high-stress red shale roadway in Kaiyang phosphate mining area, the mechanical properties and microstructure of red shale are studied. The results show that the compressive strength of the red shale is related to the bedding angle, and the strength of the 0° samples is the highest, and the strength of the 60° and 30° samples decreases gradually. With comprehensive consideration, the composite supporting method of cantilever piles and grid arch is adopted. Combining the numerical simulation and theoretical calculation, the parameters of cantilever pile with interval distance of 5 m and rock-socketed depth of 500 m are more reasonable. The monitoring results show that the roof subsidence was controlled within 250 mm, and the floor heave was within 100 mm, which could effectively control the severe deformation of the roadway and also is of great significance to the safe mining of phosphate resources. [ABSTRACT FROM AUTHOR]

Burden is one of the most important parameter which plays an immense role in rock breakage using explosive energy. It is very difficult to select the optimum burden under different geotechnical and geomining condition. The selection becomes more critical when the excavation method is underground as very few researches or studies have been carried out in such cases. Therefore, in this paper, numerical simulation-based approach has been employed to estimate the optimum burden for ring blasting. The numerical models were created under different scenario including blasthole diameter and strength of the rock. The RHT concrete constitutive model has been used in this paper to study the damage contour under different circumstances. The model output has been used to calculate the volume of rock damage along the free face. This damage volume is further correlated with various parameters. This correlation shows that the damage volume along the free face initially rises with the increase in burden and then starts decreasing after a certain value. The burden value which recorded the maximum volume of rock excavated along the free face has been considered as the optimum burden in this paper. The trial blast has been also carried out at the experimental site for twenty-four rings. The optimum burden achieved from the experimental trial for 102 mm blasthole diameter and rock having uniaxial compressive strength as 92 MPa lies between 2.4 and 2.65 m. However, the optimum burden predicted through developed empirical equation from the numerical model is 2.6 m. The study shows that the simulation-based prediction exhibits a minor deviation within 15% with the experimental result. Hence, to assess the optimum burden under various geotechnical and geomining circumstances, numerical simulation-based approach may be carried out using the proposed methodology. Highlights: Burden for ring blasting is optimised using different numerical simulation models. Volume of rock excavated along free face (EV) has been calculated in each case. The optimum burden from experimental trial and empirical data is 2.4–2.65 m. The optimum burden predicted from developed model is 2.6 m. [ABSTRACT FROM AUTHOR]

Previous investigations of rock-cutting tool interaction by normal indentation of rocks were mostly conducted at ambient pressure, a condition not representative of the lateral stresses at the excavation face. Despite recent advances in understanding rock-cutting tool interactions with lateral confinement, working out the details of the relationship between rock fracture due to indentation and confinement still requires experimental investigations and theoretical analyses. We conducted a series of normal indentation tests on samples of Gildehaus Bentheim sandstone at lateral confinement up to 20 MPa using a set-up that allowed us to monitor lateral sample deformation and acoustic-emission activity. Experimental observations show that lateral confinement has a significant effect on the load responses and suppresses sample dilation; furthermore, the propagation path of the macroscopic fracture deviates from the indentation direction as confinement increases. The peak indentation pressure increases with confinement and its occurrence is accompanied by significant dilation and acoustic emission activity indicating that it coincides with initiation of macroscopic tensile fracturing. A cavity-expansion-based theoretical model, that accounts for the increases in compressive strength and fracture toughness with lateral confinement, captures the trend of increasing indentation pressure with lateral confinement. In addition, the good agreement between theoretical predictions and experimental data indicates that lateral confinement promotes the growth of the damage zone under the indenter preceding potential macroscopic tensile failure. The model correlates thrust required to break rocks in-situ with rock strength parameters, tool shape parameters, and lateral confinement, thus providing a starting point for optimizing the design of cutting tools. Highlights: The set-up for normal indentation tests with lateral confinements allowed for monitoring the apparent lateral strain of specimens, providing information on the failure process during indentation Indentation pressure exhibits a peak in contrast to force at all confinements investigated and the peak value in indentation pressure is suitable for an indicator for fracture initiation The strengthening effect with confinement, evidenced by the increase in force that is required to break the rock, is associated with decreasing density and length of pre-existing flaws Theoretical models are proposed to integrate the influence of confinement on rock indentation, the predictions of which agree well with experimental data The strengthening effect can be accounted for by the increase in the compressive strength and in the fracture toughness as confinement increases, the former controls the damage-zone formation and the latter ultimate macroscopic failure [ABSTRACT FROM AUTHOR]

A novel electro-hydraulic servo point load meter has been developed to address the limitations of existing point load meters, which cannot provide continuous and uniform loading. This new meter enables continuous and uniform loading with variable rates, thereby reducing the dispersion of test data and offering a technical solution for revising the current point load strength calculation formula. Experimental investigations were conducted to analyze the influence of loading rates (0.1 kN/s, 0.5 kN/s, 1.0 kN/s) on the existing point load strength correction method. Four types of rock samples, namely, fine-crystalline granite, coarse-crystalline granite, siltstone and marble, were utilized in the study. Each rock sample was tested at four different sizes: 203 mm3, 303 mm3, 403 mm3, 503 mm3. The objective was to examine how the loading rate affects the accuracy and effectiveness of the point load strength correction method. Initially, the correction index "m" from various domestic and foreign regulations was employed to calculate and analyze the test data, determining the appropriate correction index m, loading rate, and range of rock sample sizes. Subsequently, the relationship between the standard point load strength and uniaxial compressive strength was analyzed based on these findings. The research results indicate the following: (1) the larger the strength of the rock sample, the smaller the point load correction index m and all four rock samples demonstrated an increase in standard point load strength when solved using the four correction indices (m1, m2, m3, m4) with increasing loading rate. (2) With increasing sample size, the standard point load strength solved using correction indices m2, m3, m4 still exhibited a significant size effect, while the dimensional effect of the standard point load strength solved using m1 was not evident. (3) The conversion factors obtained through zero-intercept linear regression analysis for fine-crystalline granite, coarse-crystalline granite, siltstone, and marble were 16.45, 15.38, 15.17 and 14.83, respectively. These results indicate that the conversion factors for rocks with lower strength are smaller compared to those with higher strength. Highlights: The impact of four different rock samples with varying sizes on the existing point load strength correction method is analyzed under three loading rates. An investigation is conducted to determine the appropriate point load strength correction index for the four rock samples. The study identifies the optimal loading rate and size range for rock samples based on the modified correction index. The relationship between standard point load strength and uniaxial compressive strength is examined. [ABSTRACT FROM AUTHOR]

This paper reports the results of thermal spallation experiments on specially dried shale samples with 3 bedding orientations (0°, 45° and 90°) under 3 flame temperatures (899 °C, 1243 °C and 1559 °C) and the 3D thermal elastic finite element modelling. Under open flame heating, continuous spallation is observed with ejection of various spalls and popping sounds. After a period of spallation, tensile fractures are formed in the samples and grow perpendicular to the heating surface, except for a sample with bedding orientation of 90° under the low temperature. Increasing flame temperature promotes ejection, popping sounds and spallation rate, but reduces the spallation starting time, spallation duration, depression diameter and depression depth. The model shows that heating induces compressive stress in the surface layer and tensile stresses beneath it. The tensile stress is found to be sufficient to generate large tensile fractures. The ratio between the induced compressive and tensile stresses increases with increasing spallation depth but little affected by the flame temperature. The spallation compressive stress increases with temperature from 29 to 51% of the uniaxial compressive strength. This stress is shown to be sufficient to cause buckling of thin layers separated from the bulk of the rock. The size of the buckling layer is smaller than the size of the spallation zone leading to a mosaic pattern seen on the surface after spallation. The results are important for further understanding of the mechanism of thermal spallation of rocks as well as large scale spallation-like processes in the Earth's crust. [ABSTRACT FROM AUTHOR]

Microbially-induced calcium carbonate precipitation (MICP) technology is a new method of soil improvement that has been proposed in recent years. However, the application of MICP technology is limited by its lower efficiency and higher cost. This paper proposes a cost-effective biogrouting method for strengthening the surface soil in a designated area of the in-situ dry sandy foundation, which with a wide range of possible applications. The unconfined compressive strength, permeability, and calcium carbonate precipitation in the soil reinforced by biosand and bio-slurry are analyzed and compared. The results show that biosand has a higher bacterial utilization rate and strengthens the reinforcement effect when the bacterial suspension is insufficient. The reduction in the use of bacterial suspension lower costs when the target reinforcement strength is predetermined. Biosand can be used to increase the efficiency of reinforcement and reduce costs by adjusting the proportion of fine particles added to decrease permeability and increase the final and early strength of the specimen. Biosand has excellent prospects for engineering applications such as reinforcement of coarse sand, rapid microbially induced calcite precipitation and in-situ soil improvement. [ABSTRACT FROM AUTHOR]

Nano-SiO2, a highly acclaimed nanomaterial for enhancing cemented soil, has shown remarkable improvements in the physical properties and microstructure of cemented soil. The organic matter content in soil plays a crucial role in determining the engineering quality of cemented soil, regardless of whether it is in a freshwater or seawater environment. Therefore, when employing Nano-SiO2 as an amendment for cemented soil, it is crucial to consider the influence of different soil types and environmental conditions on the effectiveness of the enhancement. This study presents a scientific approach for enhancing the consolidation of cemented soil by incorporating Nano-SiO2 as an additive in both freshwater and seawater environments. To ensure consistency with practical construction practices, the experiments were divided into freshwater preparation and curing groups, as well as seawater preparation and curing groups. In soils with distinct characteristics, we utilized five different gradient levels of Nano-SiO2 additives and subjected the cemented soil specimens to a 60-day immersion curing process. Subsequently, unconfined compressive strength (UCS) tests were performed on samples that had reached the specified curing age to investigate the alterations in the mechanical properties of cemented soil caused by Nano-SiO2. The internal microstructure and chemical composition of the cemented soil were analyzed utilizing scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The UCS and deformation modulus of cement soil composed of silty clay A and silty clay D with low organic matter content in fresh water environment increased by 109%, 24.7% and 117%, 43% respectively after adding 3.2% Nano-SiO2; In freshwater environments, the cemented soil composed of high-organic-matter content mucky silty clay B, muddy soil C, and dredged silt E experienced respective increases of 16% and − 27%, 2% and 42%, 6% and − 6% in UCS and deformation modulus after adding 3.2% Nano-SiO2; The UCS and deformation modulus of cemented soil with high organic matter content in seawater and freshwater environment increased by 3% and 6% (Soil B), 12% and 67% (Soil C), 23% and 27% (Soil E), respectively, after adding 3.2% Nano-SiO2; The increase of UCS and deformation modulus of cement soil by adding Nano-SiO2 is negatively correlated with the content of organic matter. in the case of cemented soil with high organic matter content in a seawater environment, the specific type of soil not only impacts UCS and deformation modulus of the soil but also influences the effectiveness of enhancement. Due to the organic matter, the rate of hydration reaction in cemented soil is reduced, resulting in a decrease in the formation of pozzolanic reaction products with SiO2. As a result, the improvement in Nano-SiO2 effectiveness is diminished. [ABSTRACT FROM AUTHOR]

A large number of waste tires are discarded every year. These waste tires will have a great impact on the environment. If they can be recycled, environmental and economic benefits can be obtained. In this paper, rubber powder is added to concrete, and a variety of analytical methods are used to study the effect of rubber powder on the performance of concrete. Experiments show that the slump of concrete decreases with the increase of rubber powder substitution rate, and the rheological performance results show that the friction force increases with the increase of rubber powder substitution rate. The compressive strength of concrete decreases with the increase of substitution rate. The results of ICP show that rubber powder will adsorb cations to affect cement hydration. Nanoindentation shows that the addition of rubber powder leads to the decrease of high-density hydration products. The results of SEM-EDS show that rubber powder will affect the Si/Ca of hydration products. The results of UPV and MIP are similar. The hydrophobicity of rubber powder and the poor compatibility with hydration products are the key factors affecting the durability of concrete. Because the rubber powder only needs to be ground to avoid the related process of cement, it can obtain good economic and environmental benefits. In practical engineering, rubber powder can be added appropriately. [ABSTRACT FROM AUTHOR]

Purpose: Nisin is a lantibiotic effective against Gram-positive microorganisms such as Streptococcus mutans. The study aimed to determine the effect of the addition of nisin to high-viscosity glass-ionomer cement (HVGIC) on its antibacterial activity, setting time, surface microhardness, and compressive strength. Methods: 1 and 3% w/w nisin were added to HVGIC before mixing. Unmodified HVGIC was the control. Agar disc diffusion, direct contact test, and scanning electron microscopy (SEM) analysis were used to evaluate antibacterial activity against S. mutans. Setting time, surface microhardness, and compressive strength were measured using Gilmore needle apparatus, digital microhardness tester, and universal testing machine, respectively. Statistical analysis included Student's t test, one-way ANOVA with Tamhane's post hoc test, and repeated-measures ANOVA. Results: As evidenced by the agar disc diffusion (p < 0.001), direct contact tests (p = 0.025), and SEM analysis of the S. mutans cell count and cell surface area (p = 0.049 and 0.003), 3% nisin had the strongest antibacterial activity. There was a dose-dependent increase in setting time (p = 0.005) and surface microhardness (p = 0.006), with no significant difference in compressive strength compared to control. Conclusion: The addition of 3% nisin to HVGIC enhances the antibacterial action against S. mutans and surface microhardness without adversely affecting setting time and compressive strength. [ABSTRACT FROM AUTHOR]

To improve the tribological properties of sulfur-containing Ni-based self-lubricating composites, FGH97-WS2-Cr-CeO2 (FWCC) were prepared by spark plasma sintering technique. All composites prepared obtained new phases CrxSy and M6C, originating from the decomposition of WS2. Homogenization and fine microstructure resulted in the best mechanical properties of the FWCC composites, with the microhardness of 542 ± 12 HV, compressive yield strength of 1910 ± 52 MPa, and flexural strength of 954 ± 34 MPa. When the composites exposed to 600 °C, the oxidation of CrxSy dominated the oxidative weight gain. The coefficient of friction and wear rate of FWCC composites both tend to decrease with increasing temperature. The optimum tribological properties of FWCC composites are obtained at 600 °C with the coefficient of friction of 0.23 and the wear rate of 0.22 × 10-5 mm3 N-1 m-1. The wear rate is two orders of magnitude lower than that of FGH97-WS2 composites (FW). This is mainly due to the synergistic effect of Cr and CeO2. The addition of Cr promotes the formation of enough Cr2O3 oxide particles during friction, while the addition of CeO2 not only enhances the adhesion of the oxide enamel layer, but also improves the high-temperature stability of the sulfide. [ABSTRACT FROM AUTHOR]

To broaden the sources of earthwork and the utilization of soda residue (SR) and fly ash (FA), SR, FA, and clay were mixed to form a soda-residue soil (SRS) by adding externally moderate content of lime or/and cement for further stabilization. Through the orthogonal scheme, 9 groups of proportions were designed. Subsequently, the unconfined compressive strength (UCS) at different curing ages was conducted. Afterward, the stress–strain pattern, the UCS and water absorption, the sensitivity of factors and levels to UCS, and the deformation modulus were analyzed. Finally, the enhancement mechanism of SRS from physicochemical reactions was explored by analyzing gradation and microstructure. The results show that the patterns of stress–strain curves on SRS at different curing ages are similar; all have obvious stress peaks, and the specimens of SRS present a brittle failure. With the extension of curing ages, the UCS of all proportions increased; the UCS of the G2 group increased the most, reaching 85.44%, and the G9 group increased the least, only 1.92%. However, the water absorption quality decreased, and G6 decreased the most (37.53%), G7 decreased the least (0.84%), and UCS and water absorption quality showed a negative correlation. The sensitivity of each factor to UCS was different; the SR was the most sensitive at 7 d, but the lime was the most sensitive at 28 d. The sensitivity of each factor level (content) to UCS remains unchanged at different curing ages. There is a linear relationship between the deformation modulus and UCS. The analysis demonstrates that the better strength properties of SRS are mainly determined by the superior gradation and the reaction of materials. [ABSTRACT FROM AUTHOR]

Soft soil concerns, due to high compressibility and low bearing capacity, prompted an investigation into stabilizing clay soil. Traditionally, binder including cement or lime has been used as stabilizers though a current requirement of alternatives is stem from environmental concerns. The study focused on the viability of using a novel binary activated blended binder composed of environmentally friendly materials, namely ground granulated blast furnace slag (GGBS) activated by cement kiln dust (CKD). The experimental work included investigating the impact of the developed binders on the Atterberg limits, standard Proctor compaction, California Bearing Ratio (CBR), unconfined compressive strength (UCS), and field-emission scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy. CBR tests were conducted after 7 days of curing or soaking, while UCS and SEM analyses were conducted after 7 and 28 days of curing. A fixed binder ratio of 9% was maintained, with GGBS blended at 25%, 50%, and 75% with CKD. For comparison, samples of untreated and treated soils with unary binders from GGBS and CKD were also prepared. Results indicated that activated binders notably decreased soil plasticity and maximum dry density, while elevating optimum moisture content, CBR, and UCS, especially in later stages of treated soil and unary GGBS binder. Unary CKD binder exhibited a similar trend to activated binders. The activating of 25% GGBS with 75% CKD provided the optimum binder which increased the mechanical strengths by about 6 times than untreated soil. SEM revealed substantial formations of C-S-H and C-A-H gel, along with ettringite, intensifying with time. This research provides viable outcomes for stabilizing clay soil using environmentally friendly binders, demonstrating significant improvements in soil properties, particularly when using the binary activated blended binder consisting of GGBS and CKD. [ABSTRACT FROM AUTHOR]

Middle-deep geothermal reservoirs, rich in energy, experience deep burial, high temperature, and intense three-dimensional stresses, causing noticeable elastic–plastic rock deformation under high confining pressure. However, existing researches primarily focused on elastic–plastic properties under various confining pressures, overlooking the impact of high temperature on granite's behavior. To address this, we conducted compression experiments at seven temperature points (25–600 °C) under varying confining pressures (0–15 MPa). The results reveal that increasing confining pressure prolongs the plastic yielding stage, linearly enhances compressive strength, and shifts rupture mode from brittle to expansion shear damage. Conversely, under constant confining pressure, compressive strength decreases with rising temperature, accompanied by more intricate artificial cracks. Rock cohesion, internal friction angle, and wave velocity decrease due to increased thermal damage micro-cracks. Heat treatment over 500 °C significantly increases porosity and pore throat radius, explaining heightened plasticity in hot dry rocks. These findings offer theoretical and technical insights for understanding elastic–plastic fracture mechanisms during hydraulic fracturing in middle-deep geothermal reservoirs and enhancing heat recovery efficiency. [ABSTRACT FROM AUTHOR]

The present study aims to assess the effect of using recycled aggregates (RA) derived from construction and demolition waste (CDW) on the development of the unconfined compressive strength (UCS) of a silty-cement soil from the Guabirotuba Formation, located in the southern region of Brazil. Was considered the influence of various parameters, including RA content, compaction effort, maximum dry specific mass, and porosity/volume cement content (η/Civ). RA contents of 10%, 20%, and 30%, combined with 5% cement by dry soil weight, are studied at curing times of 0, 7, 14, and 28 days, using standard, intermediate, and modified compaction efforts. The results reveal that the addition of RA leads to an increase in the maximum dry specific mass, directly correlating with an increase in the rate of compressive strength gain over time. In the case of the modified compaction effort, the UCS value for the mixture with 30% RA at 28 days of curing reaches 2318 kPa, which is 35% higher compared to the mixture without RA, which has an RCS value of 1711 kPa. Equations establishing a relationship between η/Civ and UCS show that smaller η/Civ values result in greater UCS. Furthermore, a correlation between η/Civ and RA content with UCS suggests that η/Civ has a stronger influence on UCS than RA content. Lastly, Scanning Electron Microscopy (SEM) indicates that incorporating 30% RA reduces the number of pores as well as their size, which enhances the soil structure and its increases stability, resulting in a more compact structure. [ABSTRACT FROM AUTHOR]

Poly (butylene adipate-co-terephthalate) (PBAT), a biodegradable polyester, has gained increasing research interest. Foam polymers based on PBAT have demonstrated high potential for various applications. Here, we propose a novel method for blending foam made of starch and PBAT. Melt blending was used to create PBAT/starch blends, and batch supercritical CO2 autoclave foaming was used to create polymer foams. We looked into the mechanical characteristics, crystallization, and dispersion morphology of PBAT/starch mixes. The structure, together with the anti-shrinkage and compressive strengths of PBAT/starch foams were investigated. The findings demonstrate that starch can be more effectively incorporated into the PBAT matrix with the aid of polyol (glycerol) and that the addition of starch with specific quantities can create a clear bimodal-like cell structure, thus increasing the matrix's rigidity and lessen the shrinkage issue with PBAT foam, resulting in foam with good compression resilience. The largest expansion ratio, 19, the least shrinking, and outstanding compression resilience were found in the 70/30 mixture of PBAT and starch. It provides a broadly applicable method for possible large-scale manufacture of biodegradable polyester foams with anti-shrinkage and high compression resilience. [ABSTRACT FROM AUTHOR]

Abstract—The possibility of using finely dispersed additives made of local mineral raw materials for the manufacture of concrete based on sulfur binder has been established. At the same time, additives with a high specific surface area contribute to the formation of uniform small sulfur crystals on the surface of fine fillers, which makes it possible to improve the strength properties of sulfur concrete. [ABSTRACT FROM AUTHOR]

Globally, bentonite is being used as a binder in iron ore pelletizing due to its high swelling index, thermal resilience, and water absorption capacity. However, the conventional use of bentonite contributes to increased gangue content (Al2O3 and SiO2) in pellets, subsequently affecting blast furnace operations in terms of high solid fuel consumption, low productivity, and high slag rates. In this work, sodium hydroxide has been used with bentonite to reduce its consumption without affecting the pellet properties. Pellets are prepared by varying the NaOH addition from 0 to 0.1 pct at an interval of 0.02 pct. Green and fired pellets were tested for green compressive strength (GCS), dry compressive strength (DCS), drop number, cold compressive strength (CCS), Hoogoven simulations (HOSIM), softening-melting, and swelling index (SI). The interaction between hematite and bentonite was studied using molecular modeling simulations (ReaxFF MD). Microstructural studies (optical and SEM-EDS) of pellets were carried out for phase quantification and to assess the chemical composition of slag phases. Besides, FactSage simulations were performed to validate the slag phase formation. It is inferred that a 50 pct reduction in bentonite consumption is possible at 0.04 pct NaOH with a 12 pct improvement in CCS. Laboratory results were validated for a seven-million-tonne pellet plant with 0.02 and 0.04 pct NaOH dosage. Plant trial shows that there is an 18 and 39 pct reduction in bentonite consumption with the addition of 0.02 and 0.04 pct NaOH dosages, respectively. [ABSTRACT FROM AUTHOR]

Disposal of water treatment sludge (WTS) has become an important issue of global environmental concern due to problems and costs. This study explored the feasibility of cold-bond methodology to produce an eco-friendly core–shell lightweight aggregate (LWA) from WTS, expanded perlite (EP), and cement. The effect of cement and WTS content on the properties of the LWA was studied. The findings revealed that the crushing strength, loose bulk density, 24-h water absorption, and 28-d water absorption of produced LWA ranged from 0.45 to 3.1 MPa, 1.05 to 1.25 g/cm3, 12.4 to 22%, and 22 to 27%, respectively. In addition, increasing the WTS content in the shell has a positive impact on the pH of the produced LWA. Furthermore, the SEM microstructure graphs revealed the efficient interference in the LWA particles between the cement–WTS composite and the perlite. The results also prove the possibility of using the produced LWA to produce structural lightweight concrete, with compressive strength, splitting tensile strength, and dry density of 24 MPa, 2.98 MPa, and 1840 kg/m3, respectively, with a consistent thermal conductivity of 0.72 W/m K and good acoustic insulation. [ABSTRACT FROM AUTHOR]

Partial replacement of conventional stabilizers with environmentally-friendly and sustainable materials has recently turned out to be a common approach to enhance the strength and stiffness properties of earthen materials. In this regard, natural zeolite and expanded polystyrene (EPS) beads are used in this study to be added to clay samples conventionally stabilized with lime. Accordingly, a systematic survey is conducted to inspect the changes in mechanical strength and shear stiffness of untreated and lime-zeolite treated reconstituted clays (with various proportions of kaolinite and montmorillonite) due to the incorporation of EPS beads. To this end, first, the optimum percentage of lime was obtained from a series of pH tests. Then, the optimum content of lime replacement with zeolite yielding the highest unconfined compressive strength (UCS) was estimated which appeared to be 25%. Afterward, all the samples were lightened by adding 0.1% and 0.25% weight ratios of EPS beads to the fine materials (η ) and the results were compared with similar samples without EPS beads. Several standard Proctor compaction, swelling, UCS, and non-destructive bender element (BE) tests were carried out on lightened samples to assess their physical properties, strength characteristics, shear wave velocity ( V s ) and small-strain shear modulus ( G max ). The samples' swelling and compaction properties decreased by incorporating the EPS beads. Strength and stiffness characteristics of lightened composites were observed to be acceptable when 0.1 % EPS beads (denoted as the optimum percentage) were included in the studied mixtures. Furthermore, to interpret microscale phenomena, scanning electron microscopy (SEM) micrographs of the interfaces of the typical untreated and treated samples are provided, which demonstrate the interlocking zones, formation of cementitious gels and the considerable volume of the clay medium occupied by deformable EPS beads leading to the significant reduction in the soil weight. Finally, using the group method of data handling (GMDH)-type neural network (NN), several statistical modelings are carried out to predict the UCS, V s , and G max of the studied mix designs, which resulted in highly accurate models. [ABSTRACT FROM AUTHOR]

Basalt powder (BP) is the residue of a plant that crushes basalt stones. This work deals with the effect of waste BP on the properties of cement mortars and the physical properties of hardened mortars. Modified concrete was prepared by partial replacement of BP in amount of 5, 10, 20% by weight of cement. Physico-mechanical properties and corrosion resistance were investigated. Electrochemical impedance spectroscopy (EIS) was used to examine the corrosion behavior of cement pastes with a partial addition of basalt powder in aggressive solutions of 5% NaCl and 5% MgCl2 for up to 270 days. Infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were also performed to investigate the hydration process and microstructure formation of the basalt blended paste. Results indicate that the addition of basalt powder as a partial replacement of cement influences the microstructure of the interfacial transition zone (ITZ), which is denser and stronger than in cement paste without basalt powder. The filler effect of the basalt powder improves the compressive strength of cement paste. Also, comparing BP0 and BP20 in 5% NaCl after 270 days, the partial substitution of cement with BP resulted in a higher compressive strength of 671 and 895 kg/cm2, respectively. The EIS results also showed the highest values of Rp 953 ohms cm2 after 270 days. This high corrosion resistance might indicate the binding by high Al2O3 that reduced the free aggressive chloride ions in the solution. Article Highlights: The addition of basalt powder as a partial replacement of cement, improved the compressive strength of the concrete. The physicochemical and mechanical investigations showed that the basalt addition led to physical densification and more ITZ robust of cement matrix. EIS measurements showed that BP20 sample in 5% NaCl had a high Rp, 953 ohms cm2 after 270 days indicated higher corrosion resistance. [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]

This study investigated the feasibility of large-scale utilizing calcareous wastes (CW) of Angoran lead and zinc mine as aggregates in mortar production with the maximum possible substitution of natural aggregates. The main goal was to produce mortar (concrete with fine aggregates as fine as sand or smaller) from Angoran mine's calcareous wastes for maintenance in its underground spaces. Compared to concrete, such mortars with better fluidity can enter narrow spaces more easily. In addition, it can be used to build various structures around the mine. Therefore, multiple samples were prepared by replacing 0% (as the control sample), 20%, 40%, 60%, 80%, and 100% of natural aggregates with CW. Subsequently, compressive strength, flexural strength, water absorption, slump, and TCLP tests were conducted on these samples. The results revealed that the mortar sample with 80% CW exhibited significantly higher compressive strength at 3, 14, 28, and 56 days compared to both the control sample and other samples. Specifically, the compressive strength of this sample reached 35.5 MPa at 56 days, representing an 18.4% increase over the control sample. This indicates that the hydration of cement and the growth of C-S–H gel were enhanced. Analysis of the workability and slump of the samples indicated that as the percentage of natural aggregate replaced by CW increased, the fluidity of the mortar slightly decreased. In addition to mechanical properties like compressive strength, environmental aspects like heavy metal stabilization are also very important. So, TCLP tests conducted on the four heavy metals lead, zinc, copper, and cadmium demonstrated that the released amounts of these elements from all the samples were below the EPA standard limits. These findings confirm the effective stabilization of heavy metals in mortar samples. A comparison of SEM images revealed that the mortar sample made with 20% CW (with minimum compressive strength) exhibited a higher presence of ettringite compared to the sample made with 80% CW (with maximum compressive strength) after 28 days. [ABSTRACT FROM AUTHOR]

This research extensively used different progressive machine learning (ML) techniques to predict the compressive strength (CS) and tensile strain (TSt) of engineered cementitious composites (ECC) with 14 input variables and six algorithms. Specifically, random forest (RF), support vector machine, extreme gradient boosting (XGBoost), light gradient boosting machine, categorical gradient boosting (CatBoost), and natural gradient boosting techniques were used in the present study, to understand mechanical properties of ECC meanwhile these properties are crucial for design codes and developing new reliable models for mixtures. The discrepancy between the ML technique and specific ECC expected outputs is novel in this study and will aid researchers in better understanding of ECC features. To estimate the CS and TSt of the ECC, 2535 and 1469 input data points, respectively, were incorporated based on the material ratio, W/B, and different properties of the fibers. In addition, hyperparameter optimization techniques have also been used in ML to improve over fitting and make the model more accurate and robust. Moreover, an error analysis was highlighted between the actual and predicted CS and TSt of the ECC with each ML technique. Also, the significance and influence of the variable inputs that affect the CS and TSt were explained using the Shapley additive explanation (SHAP) approach. Among all approaches, CatBoost and XGBoost predicted the CS and TSt of ECC with greater accuracy than other techniques in terms of the coefficient of determination (R2), mean square error, mean absolute error, root mean square error, and symmetric mean absolute percentage error. The training and testing R2 values of CatBoost and XGBoost for predicting the CS and TSt of ECC were 0.96, 0.89, 0.89, and 0.76, respectively. SHAP analysis revealed that W/B and fiber elongation were the most significant input variables for the CS and TSt of the ECC. [ABSTRACT FROM AUTHOR]

The porous TiC ceramics with different porosity were fabricated by hot-press sintering using CaO as pore-forming agent, which opened a new field to explore pore ceramics. Then a serious of porous TiC were fabricated and investigated the microstructure, porosity and mechanical properties of pore TiC. The porosity and bulk density of TiC depend on CaO content, which significantly affects the microstructure, mechanical properties and fracture behaviors. With the CaO content increasing, the porosity and pore size of TiC are increased, while the bulk density is decreased. Compressive strength and specific compressive strength exhibit a trend of monotone variation, and the maximum compressive strength is 51.3 MPa when CaO content is 40 vol%. A high porosity condition leads to a loose structure with low load-bearing capacity. As CaO content increases from 40vol% to 55vol%, porosity of TiC increases from 32.9 to 52.6%, and the compressive strength of porous TiC decreases from 51.3 MPa to 9.7 MPa. Additionally, it was concluded that porosity determine the bulk density and strength of porous TiC. However, the thermal conductivity of pore TiC increases with rising of porosity. This is attributed to the total number of pores is decrease owing to CaO agglomeration. [ABSTRACT FROM AUTHOR]