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The efflorescence problem is always an intractable problem for geopolymer. Silica fume (SF), nano-silica (NS), 5A zeolite (ZL) and nano-silica treated with silane (NST), were used to mitigate the efflorescence of fly ash (FA) - granulated blast furnace slag (GBFS) - steel slag (SS) based geopolymer. The effect of their dosages on the efflorescence was evaluated through accelerated efflorescing, leaching and unconfined compressive strength (UCS) tests. The inhibition mechanisms were explored by XRD, SEM, FTIR and MIP characterization. It revealed that SF and NS presented the most effective mitigating effect on efflorescence, with 9 % of SF and 2 % of NS totally inhibiting efflorescence and improving the compressive strength, and ZL and NST also alleviated the efflorescence at appropriate contents. Optimizing pore network and stabilizing free alkali were found to be the most important aspects for inhibiting efflorescence. The SF and NS worked efficiently in both two ways, which contained a large amount of dissolvable silicate that reacted with the excessive alkali to form C(N)-A-S-H and C-S-H gels. This filled and reduced the pores from 26 nm to less than 10 nm, and stabilized alkali with reduce the free w (Na+) by more than 50.45 %. On the other hand, ZL can solidify free alkali through the ion exchange property and fill pores due to its microaggregate nature, and NST reduced the efflorescence through blocking free alkali migration paths by hydrophobicity of the pores. These findings would guide the selection of appropriate methods to solve the efflorescence problem of geopolymers. • Reactive silicates in SF and NS can consume free alkalis to improve efflorescence resistance. • The NS inhibited free alkalis migration through optimized pore structure. • The ZL and NST mitigated efflorescence by reducing alkali leaching. [ABSTRACT FROM AUTHOR]

This research aims to produce green cement, as an alternative to traditional cement, with outstanding performance. Five alkali-activated cement pastes were fabricated based on NaOH-activation of slag (GGBFS), bypass (B), and/or silica fume (S). Codes of five pastes are C, C-20B, C-30B, C-10B10S, and C-20B10S, as C is the control paste containing 100% slag. The compressive strength of the fabricated pastes was measured at different curing regimes: Conventional curing for 3 months and autoclave curing at 4 bar/153◦C, 7 bar/178◦C, and 10 bar/198◦C for 4 h. XRD, TGA/DTG, SEM/EDX, and BET/BJH techniques were utilized to clarify the phase development, morphological and texture features of the formed alkali-activated composite pastes. Besides, the removal capacity of some pastes for methylene blue and indigo-carmine dyes from aqueous media was evaluated. The results confirmed that C and C10B10S (80%GGBFS + 10%B + 10%S) pastes have significant mechanical properties and distinctive meso-porosity that can remove both anionic and cationic dyes. [ABSTRACT FROM AUTHOR]

Nanoporous structured silica materials, namely f‐SiO2, SBA‐15, IITM‐41, and MCM‐41 were employed as the matrices for immobilizing endoxylanase by adsorption method. The equilibrium kinetics, activation energy, and thermodynamic parameters associated with endoxylanase adsorption were investigated. Our findings revealed a two‐phase adsorption mechanism: an initial phase featuring rapid adsorption rates, succeeded by a slower phase wherein adsorption gradually progressed until equilibrium was attained. Analysis of the adsorption kinetic data indicated a better fit with the pseudo‐second‐order model, suggesting chemisorption and highlighting its temperature dependency. The calculated activation energy (Ea) values fell within the range of physisorption, indicating the involvement of both types of adsorption processes. Thermodynamic assessments confirmed that the adsorption reactions were spontaneous, feasible, and endothermic. Notably, the immobilization process did not change the optimum pH of the enzyme, while the optimum temperature shifted slightly. Furthermore, immobilized enzymes show a higher reaction rate (Vmax) than the soluble XynC. All immobilized xylanases produced xylobiose (X2) to xylohexose (X6) by hydrolyzing the xylan substrate. Recycling studies showed that up to 80 % of the yield was retained after seven cycles of reuse. Our study demonstrates the potential of nanostructured silica as an effective immobilization matrix for enzymes of industrial significance. [ABSTRACT FROM AUTHOR]

The performance of the Ca(OH) 2 –Al 2 O 3 –SiO 2 –H 2 O hydroceramic system (with and without Al 2 O 3) as a potential well cementing material was investigated from both macroscopic and microscopic perspectives. To simulate the harsh conditions typical of deep wells, marked by high temperature and pressure, the material was cured at 240 °C and 50 MPa. Several hydroceramic systems with varying compositions were designed and a retarder was used to optimize the thickening time of all systems. Finally, the optimized hydroceramic systems were cured for different periods ranging from 2 to 90 days to investigate their long-term stabilities. It is found that the raw materials with finer particle sizes and higher reactivity (such as silica fume and nano-activated alumina) could improve the performance of the hydroceramic system, evidenced by increased compressive strengths and decreased permeability. Changing the Ca/Si molar ratio within the range from 2:1 to 1:1 had little effect on the physical and mechanical properties of the hydroceramic system, despite significant variations in the composition of hydration products. The hydroceramic systems exhibited good stability over a curing period from 2 to 30 days, but strength retrogression phenomenon was observed during longer curing periods from 30 to 90 days. Microscopic evaluations revealed that the strength retrogression could be due to the formation of reyerite in high calcium systems, while it was the conversion of amorphous C–S–H to xonotlite that led to the strength retrogression in low calcium systems. [ABSTRACT FROM AUTHOR]

This first part of the work is devoted to development of high-performance cement composites (HPCCs) with aim to elaborate a mix design methodology for obtaining defined properties of HPCC with industrial by-products such as fly ash, silica fume, and colloidal silica. The research employs innovative methods of experimental design and response surface optimization to find a compromise between the set compressive strength and mix workability. Stage 1 consists in selecting appropriate raw materials and designing an initial mix. Stage 2 involves finding an optimal dosage of superplasticizer. Stage 3 is the response surface optimization, which includes experiment planning with variable parameters x1 (fly ash) and x2 (nanosilica), conducting practical experiments, results of analysis and approximation, using mathematical models of 1st, 2nd, and 3rd order polynomials. The final Stage 4 implies finding the optimal compromise solution between strength and mix flowability, as well as experimental validation of the results obtained. The approach developed can be used for the design of similar multi-component mixes. [ABSTRACT FROM AUTHOR]

This study was carried out to investigate the chemical, mechanical, and structural properties of increasing amounts of fumed silica added to PMMA denture base material. The effect of adding fumed silica at three different concentrations (0.5%, 1%, and 2% by weight) to PMMA was studied using Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), density, flexural strength, hardness, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The results showed that the highest flexural strength values (105.64 MPa) and hardness (20.07 microvickers) were obtained with 1% wt. of fumed silica material. According to DMA results, fumed silica samples containing 1% wt. had the highest energy storage (3.24 GPa at 30 °C) and glass transition temperature. As a result, fumed silica in PMMA denture base material reached its maximum saturation limit at 1% wt. A more brittle behavior was observed in samples containing 2% fumed silica, which accumulated on the surface, as confirmed by AFM. The molecular bonds at the resin-fumed silica interface weaken due to the agglomeration of fumed silica. Consequently, the flexural strength and hardness decrease, along with the glass transition temperature and storage modulus. The potential applications of this research are vast, inspiring further exploration and innovation in denture-based materials. [ABSTRACT FROM AUTHOR]

Heavy-weight concrete (HWC) is a widely adopted radiation shielding material in the nuclear industry. In this study, two kinds of high-density aggregate, namely, iron sand (IS) and steel slag coarse aggregate (SSCA), were adopted to fully replace river sand and natural coarse aggregate, respectively, producing ultra-heavy-weight concrete (UHWC) with a unit weight >3800 kg/m3, to ensure excellent radiation shielding performance. However, IS and SSCA seriously impaired the passing ability of UHWC as the cement paste could not hold the IS and SSCA as firmly as natural aggregates, owing to their high density. To overcome this, the rheology of UHWC should be optimised by partially replacing the cement with superfine silica fume (SSF) and using a suitable amount of superplasticiser (SP) to enhance the wet packing density (WPD). A total of 28 UHWC mixes with different replacement ratios of SSF and different SP dosages were tested for segregation width, flowability, L-box passing ability, unit weight and WPD. Results revealed that incorporating an appropriate quantity of SSF and SP improved the WPD of UHWC, resulting in improved segregation resistance, enhanced flowability, increased passing ability and a higher unit weight. Lastly, there is a positive correlation between flowability, passing ability and WPD. [ABSTRACT FROM AUTHOR]

To address the environmental impact of greenhouse gases in cement production, incorporating cement substitute materials is crucial. However, the slow degradation of discarded tires poses environmental challenges, making burial or incineration unsustainable. This study explores the integration of discarded tires as crumb rubber in concrete and the use of silica fume as a cement substitute. Experimental methods, coupled with neurofuzzy systems, were employed to predict the mechanical properties of the resulting modified concretes. In the experimental approach, silica fume replaced cement at weight percentages of 0%, 10%, 12%, and 15%, while crumb rubber substituted sand at volume percentages of 0%, 10%, and 25%. Compressive and flexural strengths were evaluated at seven, 28, and 90 days, with tensile strength assessed at 28 days. The neurofuzzy system utilized six inputs—cement, gravel, sand, silica fume, water–cement ratio, and sample age—to forecast tensile and compressive strength in silica fume-containing concrete. Similarly, six inputs—cement, gravel, sand, crumb rubber, water–cement ratio, and sample age—were used to predict flexural and compressive strength in rubber-containing concrete. The findings reveal that the inclusion of silica fume enhances the mechanical properties of concrete, while the introduction of crumb rubber diminishes these properties. Specifically, a quantitative analysis demonstrates the positive impact of silica fume on the strength and contrasting effect of crumb rubber. The neurofuzzy system exhibits remarkable accuracy in predicting tensile and compressive strength for silica fume-containing concrete and flexural and compressive strength for rubber-containing concrete. [ABSTRACT FROM AUTHOR]

In this study, the combined effects of Expired Cement (EC) fly ash lightweight aggregate (ECFLA), silica fume (SF), and fly ash (FA) were utilized as sustainable alternatives for self-consolidating lightweight concrete (SCLC). The ECFLA was produced by a cold bonding pelletization process using 20% EC and 80% FA mixed by weight in a tilted pan and moisturized with water. A total of 12 mixtures were prepared in four groups; the control group the natural aggregate was replaced with partial and full ECFLA coarse aggregates at 0%, 50%, and 100% levels. Also, 20% FA, in the second group and 10% SF third group were in a binary blend replacement of cement, the fourth group, ternary blend was used with the mentioned admixtures. The mechanical properties of SCLC, including compressive, flexural, and splitting strengths as well as elastic modulus, were evaluated. Furthermore, the drying shrinkage behavior of the mixtures was monitored over a 90-day drying period. The results revealed that the density of structural lightweight concrete reached 1830 kg/m³ with full replacement of normal concrete with ECFLA. Moreover, the compressive strength indicated a decrease of approximately 16.3% and 23% with 50% and 100% replacement of ECFLA, respectively than the reference mixture with normal aggregate at 28 days. However, the negative effects of ECFLA in SCLC can be improved with binary and ternary mineral admixtures. [ABSTRACT FROM AUTHOR]

Self‐compacting concrete (SCC) is a specialized type of concrete that features excellent fresh properties, enabling it to flow uniformly and compact under its weight without vibration. SCC has been one of the most significant advancements in concrete technology over the past two decades. In efforts to reduce the environmental impact of cement production, a major source of CO2 emissions, silica fume (SF) is often used as a partial replacement for cement. SF‐modified SCC has become a common choice in construction. This study explores the effectiveness of soft computing models in predicting the compressive strength (CS) of SCC modified with varying amounts of silica fume. To achieve this, a comprehensive database was compiled from previous experimental studies, containing 240 data points related to CS. The compressive strength values in the database range from 21.1 to 106.6 MPa. The database includes seven independent variables: cement content (359.0–600.0 kg/m3), water‐to‐binder ratio (0.22–0.51), silica fume content (0.0–150.0 kg/m3), fine aggregate content (680.0–1166.0 kg/m3), coarse aggregate content (595.0–1000.0 kg/m3), superplasticizer content (1.5–15.0 kg/m3), and curing time (1–180 days). Four predictive models were developed based on this database: linear regression (LR), multi‐linear regression (MLR), full‐quadratic (FQ), and M5P‐tree models. The data were split, with two‐thirds used for training (160 data points) and one‐third for testing (80 data points). The performance of each model was evaluated using various statistical metrics, including the coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE), objective value (OBJ), scatter index (SI), and a‐20 index. The results revealed that the M5P‐tree model was the most accurate and reliable in predicting the compressive strength of SF‐based SCC across a wide range of strength values. Additionally, sensitivity analysis indicated that curing time had the most significant impact on the mixture's properties. [ABSTRACT FROM AUTHOR]

Significant amounts of waste material are generated at various stages of andesite stone processing, including mining, cutting, and polishing. Despite this, limited research has been conducted on the potential use of waste andesite powder (WAP) as a mineral admixture. The impact of WAP on the high‐temperature resistance of cement‐based composites remains largely unexplored. This study aims to evaluate the benefits of incorporating WAP as a partial substitute for Portland cement. Self‐compacting mortars (SCMs) with varying WAP replacement rates (5%–30%) were produced and subjected to temperatures of 300°C, 600°C, and 900°C. Additionally, ternary mixtures of WAP and silica fume were produced for comparative analysis. The results showed that SCMs containing up to 10% WAP exhibited higher 90‐day compressive strength compared to the control sample. Furthermore, WAP inclusion improved high‐temperature resistance, and the use of WAP at higher replacement rates was feasible when combined with mineral admixtures possessing high pozzolanic activity, such as silica fume. [ABSTRACT FROM AUTHOR]

The improper disposal of industrial wastes will cause environmental pollution and economic losses due to the loss of active ingredients. Solid waste silica fume and pyrolusite powder were used to synthesize quartz ceramic proppant by pelleting and sintering to replace natural quartz sand for unconventional oil and gas exploitation. The effects of pyrolusite powder content and sintering temperature on the apparent density, breakage ratio, and acid solubility of the proppant were thoroughly studied. The phase composition and microstructure of the proppant were characterized by X‐ray diffraction and scanning electron microscopy, respectively. The results revealed that the main crystal phase of the proppant prepared without pyrolusite was cristobalite, while that with pyrolusite was cristobalite and quartz, and the content of quartz phase increased gradually with increasing the pyrolusite content. The addition of pyrolusite remarkably increased the density and improved the performance of the proppant due to the resulting glass phase at high temperatures and the presence of andradite. As adding 20% pyrolusite, the apparent density of the proppant sintered at 900°C was 2.26 g/cm3, while the breakage ratio under 28 MPa closed pressure and acid solubility reached the minimum, 9.89% and 5.3%, respectively, meeting the industrial standard requirements. [ABSTRACT FROM AUTHOR]

Structural lightweight concrete (SLWC) is crucial for reducing building weight, reducing structural loads, and enhancing energy efficiency through lower thermal conductivity. This study explores the effects of incorporating silica fume (SF), micro-polypropylene (micro-PP), and macro-PP fibers on the workability, thermal properties, and strength of SLWC. SF was added to all mixtures, substituting 10% of the Portland cement (PC), except for the control mixture. Macro-PP fibers were introduced alone or in combination with micro-PP fibers at volumetric ratios of 0.3% and 0.6%. The study evaluated various parameters, including slump, Vebe time, density, water absorption (WA), ultrasonic pulse velocity (UPV), thermal conductivity coefficients (k), compressive strength (CS), and splitting tensile strength (STS) across six different SLWC formulations. The results indicate that while SF negatively impacted the workability of SLWC mortars, it improved CS and STS due to the formation of calcium silicate hydrate (C-S-H) gels from SF's high pozzolanic activity. Additionally, using micro-PP fibers in combination with macro-PP fibers rather than solely macro-PP fibers enhanced the workability, CS, and STS of the SLWC samples. Although SF had a minor effect on reducing thermal conductivity, the use of macro-PP fibers alone was more effective for improving thermal properties by creating a more porous structure compared to the hybrid use of micro-PP fibers. Moreover, increasing the ratio of micro- and macro-PP fibers from 0.3% to 0.6% resulted in lower CS values but a significant increase in STS values. [ABSTRACT FROM AUTHOR]

The hydration heat of a four-component binder consisting of Portland cement (CEM I 42.5 R), blast-furnace slag (BFS), metakaolin (MK), and silica fume (SF) was investigated using a conduction calorimeter and thermal analytical method to optimize the material composition of self-compacting mortar (SCM). Then, the influence of material composition with different substitution levels (0, 25, 30, and 35% labelled as SCM100, SCM75, SCM70, and SCM65) on physical and mechanical properties of the mortars with two volumetric binder sand ratios of 1:1 and 1:2 (cement: sand) was evaluated. Furthermore, two mortar compositions comprising SCM75 and sand at 1:1 and 1:2 ratios were used to prepare fibre-reinforced self-compacting mortars in five combinations (0, 0.25, 0.5, 0.75, and 1%) of two fibres (polypropylene-PPF and basalt-BF) at a constant content of 1.00 vol%. The properties of the prepared samples were investigated with respect to the characteristics of self-compactibility and mechanical properties of fresh and hardened states, respectively. The rheology characteristics expressed by slump flow, V-funnel, and T20 were found following the EFNARC guidance. The partial replacement of cement by supplementary cementitious materials has enhanced the performances (compressive and flexural strengths, dynamic modulus of elasticity) of self-compacting mortars from the 7th day through pozzolanic activity. Furthermore, adding fibres has enhanced the DME and microstructure of the self-compacting mortars. [ABSTRACT FROM AUTHOR]

The present study focuses on the mechanical performance of steel and polyvinyl alcohol fibers embedded in the geopolymer matrix. A high-strength geopolymer concrete with fly ash, slag and silica fume as precursors and sodium hydroxide and sodium silicate solutions as activators has been tested for its strength in compression and flexure. The influence of fibers on flowability, long-term shrinkage and sulphuric acid attack on the geopolymer concrete has also been studied. The dosage of fibers was maintained at 1%, 2% and 3% by volume, and fibers of length 13 mm have been used in the study. Results indicate that slag with 3% steel fibers by volume had a predominant influence on the strength development of steel fiber-reinforced geopolymer concrete, yielding a compressive strength of 107 MPa after 28 days. Blast furnace slag resulted in increasing the shrinkage of concrete due to rapid gel formation owing to the presence of calcium ions, although the fibers helped reduce the shrinkage to some extent. The strength of steel fiber geopolymer concrete was superior to PVA fiber geopolymer concrete; however, after an acid attack, the strength of steel fiber geopolymer concrete was reduced more than PVA fiber geopolymer concrete due to the enhanced corrosion resistance of PVA fibers. [ABSTRACT FROM AUTHOR]

This study aimed to utilize the hydration characteristics of cement through wet grinding techniques to efficiently and conveniently prepare a stable C-S-H seed suspension, providing key parameters and a scientific basis for their large-scale production, which ensures the stability of the C-S-H suspension during production, transportation, and application. This preparation aimed to mitigate the adverse effects of high-volume silica fume on the early mechanical properties of high-performance cement concrete. The properties of C-S-H seed were characterized in detail by SEM, XRD, and TD. In the concrete performance test, silica fume was used to replace part of the cement, and different contents of C-S-H seed were added to test its effect on the compressive strength of concrete, with XRD and SEM used to analyze the performance differences. The results show that the particle size and hydration degree of cement no longer developed after 90 min of wet grinding. Polycarboxylate ether (PCE) superplasticizer can increase the fluidity of the crystal C-S-H seed suspension when the content exceeds 1.5%. When the content of PCE exceeded 2%, the C-S-H seed suspension precipitated. Adding 5% C-S-H seed can increase the compressive strength of cement concrete by 10% under the condition of reducing the amount of cement and increasing the amount of silica fume. And Ca(OH)2 (CH) was produced by cement hydration consumed by silica fumes to generate C-S-H gel, by which the concrete became denser with more strength. However, when the amount of C-S-H seed exceeded 7%, the compressive strength of the concrete decreased. [ABSTRACT FROM AUTHOR]

Extensive research has been conducted on the sulfate attack of concrete structures; however, the need to adopt the use of more sustainable materials is driving a need for a quicker test method to assess sulfate resistance. This work presents accelerated methods that can reduce the time required for assessing the sulfate resistance of mixtures by 70%. Class F fly ash has historically been used in concrete mixtures to improve sulfate resistance. However, environmental considerations and the evolving energy industry have decreased its availability, requiring the identification of economically viable and environmentally friendly alternatives to fly ash. Another challenge in addressing sulfate attack durability issues in concrete is that the standard sulfate attack test (ASTM C1012) is time-consuming and designed for only standard mortars (not concrete mixtures). To expedite the testing process, accelerated testing methods for both mortar and concrete mixtures were adopted from previous work to further the development of the accelerated tests and to assess the feasibility of testing the sulfate resistance of mortar and concrete mixtures rapidly. This study also established criteria for interpreting sulfate resistance for each of the test methods used in this work. A total of 14 mortar mixtures and four concrete mixtures using two types of Portland cement (Type I and Type I/II) and various supplementary cementitious materials (SCMs) were evaluated in this study. The accelerated testing methods significantly reduced the evaluation time from 12 months to 21 days for mortar mixtures and from 6 months to 56 days for concrete mixtures. The proposed interpretation method for mortar accelerated test results showed acceptable consistency with the ACI 318-19 interpretations for ASTM C1012 results. The interpretation methods proposed for the two concrete sulfate attack tests demonstrated excellent consistency with the ASTM C1012 results from mortar mixtures with the same cementitious materials combinations. Metakaolin was shown to improve sulfate resistance for both mortar and concrete mixtures, while silica fume and natural pozzolan had a limited impact. Using 15% metakaolin in mortar or concrete mixtures with Type I/II cement provided the best sulfate resistance. [ABSTRACT FROM AUTHOR]

The concrete compressive strength is essential for the design and durability of concrete infrastructure. Silica fume (SF), as a cementitious material, has been shown to improve the durability and mechanical properties of concrete. This study aims to predict the compressive strength of concrete containing SF by dual‐objective optimization to determine the best balance between accurate prediction and model simplicity. A comprehensive dataset of 2995 concrete samples containing SF was collected from 36 peer‐reviewed studies ranging from 5% to 30% by cement weight. Input variables included curing time, SF content, water‐to‐cement ratio, aggregates, superplasticizer levels, and slump characteristics in the modeling process. The gray wolf optimization (GWO) algorithm was applied to create a model that balances parsimony with an acceptable error threshold. A determination coefficient (R2) of 0.973 demonstrated that the CatBoost algorithm emerged as a superior predictive tool within the boosting ensemble context. A sensitivity analysis confirmed the robustness of the model, identifying curing time as the predominant influence on the compressive strength of SF‐containing concrete. To further enhance the applicability of this research, the authors proposed a web application that facilitates users to estimate the compressive strength using the optimized CatBoost algorithm by following the link: https://sf-concrete-cs-prediction-by-javid-toufigh.streamlit.app/. [ABSTRACT FROM AUTHOR]

Given the challenges encountered in injecting grout into micro-cracked rock masses, a modified ultrafine cementitious grout material (MUCG) was developed using ultrafine cement, polyvinyl alcohol (PVA) fibers, and a high-efficiency superplasticizer. To identify the optimal ratio of constituents for grouting these rock masses, extreme difference and multiple linear regression analyses were conducted based on test results of flowability and mechanical properties. A mix comprising 9% silica fume, 0.2% bentonite, 0.3% PVA fibers, 0.15% superplasticizer, and 2% setting accelerator was identified as the optimal mix. The microstructure characteristics of the optimal MUCG (MUCGop) grout cemented body were analyzed using XRD, FTIR, BET, and SEM. XRD and FTIR analyses indicated that a substantial amount of C-(A)S-H gel, CH, and AFt were formed within the first 3 days, highlighting the early strength characteristics of MUCGop. Over time, the content of C-A-H stabilized at 22%, the amount of CH decreased from 19% to 14%, whereas the amount of AFt increased to 15.9% by Day 28. Unexpectedly, CaCO3 content increased due to carbonation, reaching 37.3% by Day 28. BET and SEM analyses demonstrated that the specific surface area and porosity (most probable pore size) gradually decreased over time. At various ages, mesopores (cumulative pore diameter, median pore diameter) initially increased and then decreased. Micro-cracks appeared in the cemented body by Day 7, resulting in a slight decrease in strength (3.92%) from Day 3 to Day 7. The formation of well-developed needle-like AFt, C-(A)S-H gel, and small-volume plate-like CH contributed to uniform cementation and a denser structure. From Day 7 to Day 28, there was a slight increase in strength, by an amount of 10.66%. These findings have significant scientific implications for understanding the mechanisms of grouting reinforcement in micro-cracked rock masses. [ABSTRACT FROM AUTHOR]

The construction industry contributes the highest carbon dioxide (CO2) emissions, in which concrete production is one of the key components. Extracting and transporting raw materials such as limestone and aggregates contribute to habitat destruction and pollution. This study deals with the relative assessment of a group of commonly used concretes at varied strength levels using emergy analysis and life-cycle assessment (LCA). Six types of concrete are considered for evaluation: normal, binary blended, ternary blended, quaternary blended, alkali-activated and recycled aggregate concrete (RAC). Emergy analysis considers different qualities and quantities of inputs, providing insights on resource-based impacts through emergy indicators. LCA, conducted using the SimaPro software, evaluates the environmental impacts of concrete production using midpoint and endpoint indicators. From emergy analysis, it is observed that concrete with alternative materials such as fly ash, silica fume, ground granulated blast-furnace slag and recycled aggregate exhibits better results in terms of emergy indicators. RAC shows the highest value of emergy sustainability index in all strength ranges. In LCA, higher impacts are seen for normal concrete, followed by those for RAC. To obtain a more inclusive result, an integrated emergy–LCA index is proposed. The results from this index aid in improved decision making regarding the sustainability of the system considered. [ABSTRACT FROM AUTHOR]

This study aims to develop new ternary blend (TB) cement-free binder materials as an alternative to conventional cement by using Paper Sludge Ash (PSA) waste as the base material. During this research, the combined application of mechanical activation (grinding) and chemical activation by blending with pozzolanic: (silica fume; SF) and (rice husk ash; RHA), and high al-kalinity: (poultry litter fly ash; PLFA) and (cement kiln dust; CKD) materials were investigated. The research plan included four stages in which PSA was activated and replaced with the above-mentioned materials until reaching a ternary blend binder with the best performance (depending on the mortar compressive strength). Thereafter, the performance of this ternary blend binder was compared with the conventional cement by conducting compressive strength (at the ages of 3, 7 and 28 days) and Scanning electron microscopy (SEM) tests. The findings indicated that a cement-free binder material was developed by using a combination of 60% PSA that was blended with 20% RHA and 20% PLFA. The new binder has shown higher compressive strength than the conventional cement by about 12% after 28 days of curing. [ABSTRACT FROM AUTHOR]

The self-healing of cracks via biomineralization in bacteria-based concrete has shown remarkable results in recent decades. This novel technique uses the ability of bacteria to precipitate CaCO3 for sealing cracks, and is termed microbially induced calcite precipitation (MICP). However, most previous studies focused on extensive laboratory-based procedures before incorporating them into concrete. This investigation developed a ready-to-use silica fume (SF) based bacterial agent that can be used directly to achieve CaCO3 precipitation. This will aid in the use of MICP for field-scale repair in concrete structures. Furthermore, most previous studies addressed crack remediation in the horizontal orientation of concrete structures. This study developed a remediation strategy to repair realistic cracks in existing concrete structures. The developed SF-based inoculum at an age of 180 days stored at 4°C was used to design biocementitious grouts. Various biogrouts were examined for fresh and hardened properties in order to develop the most effective biogrout. The effectiveness of the surface restored using biogrout was evaluated in terms of mechanical and watertightness properties. Microstructural analysis was conducted at the end of testing to evaluate its physicochemical attributes. The electromechanical impedance technique was used to quantify the microbial activity in the biorestored concrete during curing. The results suggested that precipitates led to the densification of pores, ultimately lowering the water permeability and the recovery of mechanical strength of the repaired specimens. Conclusively, the SF-based bacterial agent can increase MICP activity to seal cracks in actual concrete structures. [ABSTRACT FROM AUTHOR]

This study aims to enhance the high-temperature resistance of ultrahigh-performance concrete (UHPC) by optimizing the cement-fly ash-silica fume ternary cement matrix composition and the geometric characteristics of the plastic fibers. The UHPC was designed and prepared with the cement-fly ash-silica fume ternary cement matrix through simplex centroid method and 2% volume fraction steel fiber. Polypropylene fibers with different geometric characteristics were incorporated to enhance the high-temperature resistance. The fire resistance is examined through the high-temperature exposure test. The initial bursting temperature is recorded, and the deterioration of mechanical performance is characterized. It was found that the decrepitation temperature of UHPC first increases and then decreases with the fly ash (FA) content. Meanwhile, the influence of the silica fume (SF) and cement content on the decrepitation temperature is not obvious. The optimum mix ratio of 50%–65% cement, 20%–30% FA, and 10%–20% SF is recommended to prepared the cementitious matrix with 450°C or higher initial burst temperature. The crack mouth opening displacement (CMOD) test assisted with digital image correlation (DIC) examination is conducted to characterize the fracture performance before and after high-temperature exposure. It was found that the fracture resistance of UHPC first increases and then decreases with the silica fume content, which reaches the maximum value of 16.64 N/mm with 27% SF content. Meanwhile the high-temperature resistance of UHPC increases and then decreases with the increase of the length of the doped polypropylene (PP) fibers. The added 1.2% volume fraction PP fiber can resolve the spalling issues of the UHPC materials, and the residual compressive strengths after exposure to 1,000°C of UHPC samples containing 15 mm–18 μm and 15 mm–33 μm fibers can exceed 50 MPa. This study can serve as a solid base for the fire resistance design of UHPC materials in field construction. [ABSTRACT FROM AUTHOR]

It was found that silica fume can reduce the maximum hydration heat release rate of cement by microcalorimetry, inhibit CAH10, promote the generation of C3AH6 and strätlingite C2ASH8, or promote the conversion of CAH10 to C3AH6. Sodium tripolyphosphate can retard the early hydration of cement, have a slight effect on 1 d hydration products of cement and inhibit the generation hydration products. Sodium tripolyphosphate and silica fume can promote the early hydration of cement, advance the formation of C2ASH8 or the conversion from CAH10 to C3AH6 at 1 d. [ABSTRACT FROM AUTHOR]

This study experimentally investigated the compressive strength of short concrete columns reinforced with steel or Glass Fiber Reinforced Polymer (GFRP) bars, using normal aggregate, Recycled Demolition Aggregate (RDA), or Recycled Demolition Concrete (RDC). The study variables included the concrete aggregate type, percentage of aggregate replacement, percentage of cement replaced by Micro Silica Fume (MSF), percentage of added Super-Plasticizer (SP), and the main reinforcement material. Twenty column specimens with dimensions of 150 mm x 150 mm x 700 mm were tested, with ten of them having been reinforced using steel bars and ten using GFRP bars. The results indicated that columns with GFRP bars had higher ultimate load values than their steel-reinforced counterparts. However, the ultimate load of the columns with replaced aggregate was lower than that of the reference column with normal concrete and decreased with an increasing percentage of replaced aggregate. These findings provide insights into the potential use of recycled demolition materials and GFRP reinforcement in short concrete columns while highlighting the impact on compressive strength and ductility. [ABSTRACT FROM AUTHOR]

The use of Supplementary Cementitious Materials (SCMs) in the construction industry to reduce the carbon footprint associated with cement manufacturing is increasing worldwide. This study examined the synergistic behavior of two SCMs, Fly Ash (FA) and Silica Fume (SF), in the production of HighPerformance Concrete (HPC). Using various amounts of SF and FA to replace cement, several ternary mixes were created and their strength, microstructure, durability and fresh state properties were evaluated. A Rapid Chloride Permeability test (RCPT) was performed to determine the resistance of the mixture to chloride ion penetration. Microstructural analysis was carried out utilizing Scanning Electron Microscopy (SEM) images to study the morphological characteristics of the mixes. The results revealed that the combined use of SF and FA in HPC significantly increased its durability and compressive strength owing to the pozzolanic reaction and filler effect. Microstructural investigation exhibited improved particle packing, refined pore structure, and the creation of more Calcium Silicate Hydrate (CSH) phases. Thus, SF and FA, when used in conjugation, optimize HPC performance and promise to be a sustainable and viable solution for reducing cement requirements. [ABSTRACT FROM AUTHOR]

The growing consumption of natural resources to meet the needs of road construction has become a significant challenge to environmental sustainability. Additionally, the increase in industrial by-products has raised global concerns due to their environmental impacts. The utilization of industrial by-products in asphalt mixtures offers an effective solution for promoting sustainable practices. The objective of this article is to conduct a bibliometric analysis and citation-based review to characterize and analyze the scientific literature on the use of steel slag aggregates, copper slag, phosphorus slag, bottom ash, fly ash, red mud, silica fume, and foundry sand in asphalt mixtures. Another aim is to identify research gaps and propose recommendations for future studies. The bibliometric analysis was conducted using VOSviewer software version 1.6.18, focusing on authors, co-authorship, bibliographic coupling, and countries. A total of 909 articles were selected for the bibliometric analysis. The findings indicate that more effort is needed to expand the application of industrial by-products in asphalt mixtures. Furthermore, these by-products should be utilized in different types of asphalt mixtures. The incorporation of industrial by-products into asphalt mixes also requires field validation and further laboratory investigations, particularly concerning aging and moisture resistance. In addition, the effects of chemical reactions involving industrial by-products on the long-term performance of asphalt layers should be evaluated. Finally, this article encourages engineers and researchers to intensify their efforts in utilizing industrial by-products for environmental sustainability. [ABSTRACT FROM AUTHOR]

Developing green, low-carbon building materials has become a viable option for managing bulk industrial solid waste. This paper presents a kind of all solid waste cementitious material (SWCM), which is made entirely from six common industrial wastes, including carbide slag and silica fume, that demonstrate strong mechanical properties and effectively stabilize aeolian sand (AS). Initially, we investigated the mechanical strength of waste-based cementitious materials in various mix ratios, focusing on their ability to stabilize river sand (RS) and aeolian sand. The results show that it is necessary to use alkaline solid waste carbide slag to provide a suitable reaction environment to achieve the desired strength. In contrast, the low reactivity of coal gangue powder did not contribute effectively to the strength of the cementitious material. Further orthogonal experiments determined the impact of different waste dosages on the strength of stabilized AS. It was found that increasing the amounts of carbide slag, silica fume, and blast furnace slag powder improved strength, while increasing fly ash first increased and then decreased strength. In contrast, higher additions of desulfurization gypsum and coal gangue powder led to a continuous decrease in strength. The optimized mix is carbide slag—desulfurization gypsum—fly ash—silica fume—blast furnace slag powder in a ratio of 4:2:2:3:3. The experimental results using SWCM to stabilize AS indicated a proportional relationship between strength and SWCM content. When the content is ≥20%, it meets the strength requirements for road subbases. The primary hydration products of stabilized AS are C-(A)-S-H, AFt, and CaCO3. Increasing the SWCM content enhances the reaction degree of the materials, thereby improving mechanical strength. This study highlights the mechanical properties of cementitious materials made entirely from waste for stabilizing AS. It provides a reference for the large-scale utilization of industrial solid waste and practical applications in desert road construction. [ABSTRACT FROM AUTHOR]

Encapsulating materials for light‐emitting diodes (LEDs) with optical‐grade polymeric resin is essential to protect from external environments and to improve light‐extraction efficiency (LEE) in micro‐scale LED (µ‐LED). In addition, the formation of microlens can further enhance the optical performance of µ‐LED. However, previously developed materials have limitations due to a lack of rheological properties and thermal stability. Here, the fabrication of sol–gel derived phenyl siloxane hybrid (PSH) that has a high refractive index (n), for use as an encapsulating material for µ‐LEDs is reported. Fumed silica nanoparticles (FSNs) are mixed with the PSH to yield siloxane/silica nanocomposites that have thixotropic properties, which enable the formation of microlens arrays. Optimizing the concentration of FSN in the nanocomposites yields a siloxane/silica nanocomposite that has a high n = 1.590 at 486 nm, high thixotropic index = 3.956, and increased optical haze (79.83% at 550 nm) makes light scattering. The use of PSH significantly increases the LEE of the LED (124.6% increase compared to an LED that does not use it). Finally, the siloxane/silica nanocomposite is used to direct‐dispense microlenses on µ‐LEDs in arrays. The encapsulation strategy can increase both the LEE and reliability of µ‐LEDs. [ABSTRACT FROM AUTHOR]

In this study, it is aimed to predict the performance of concretes obtained by using supplementary cementitious materials (SCM) before and after high temperature using artificial neural network. Thus, in addition to contributing to sustainable development and circular economy by using waste materials in concrete production, predicting concrete strength using artificial neural network without the need for experimental studies will provide a great advantage in practice. In addition, it will also contribute to the literature in terms of determining the optimum amount of metakaolin to be used with fly ash in concrete production. Metakaolin, silica fume and fly ash were used as SCM in different proportions in concrete mixes. Accordingly, a total of 22 concrete series were prepared, one of which was the control series. Porosity, ultrasonic pulse velocity, pressure and tensile strength tests were applied to the series at the end of 7th, 28th and 90th curing periods before high temperature. In order to determine the strength losses after elevated temperature, porosity and compressive strength tests were applied at temperatures of 400, 600 and 800 °C. Mineral additive series showed positive mechanical properties up to 20%. However, it has been observed that the use of fly ash after a certain rate causes a decrease in strength. After elevated temperature, strength loss was observed in all series due to the increase in temperature, while it was observed that the rate of being affected by elevated temperature decreased as the percentage of metakaolin increased. Optimum mineral additive usage percentages were determined as 10% fly ash and 15% metakaolin. On the other hand, the use of mineral additives above the optimum level caused the performance of the concrete to decrease. Then, the concrete compression strengths obtained at 7th, 28th, and 90th days and at 400, 600 and 800 °C temperatures are taken as the outputs of the ANN. The artificial neural network provided the closest results to experimental data. Moreover, to prove the predictive performance of ANN, a comparative analysis was made with GPR, SVM and LR and the smallest value of the RMSE value is obtained with the ANN model. Finally, a fivefold cross-validation criteria was used to objectively present the performance of the model. [ABSTRACT FROM AUTHOR]

AbstractBrick (BR) and roof tile (RT) fine aggregate fractions derived from construction and demolition wastes have a low recycling rate in new construction and building materials. This article assesses their suitability for replacing the limestone aggregate in foam concrete, which helps valorise such fractions and conserve natural limestone resources. Two concrete categories containing or not silica fume (SF) were investigated, while the BR and RT aggregate replacement rates were 10%, 20% and 40%. Tested properties include flow, density, water absorption, porosity, thermal conductivity, mechanical strengths, microscopy, drying shrinkage, resistance to freeze/thaw cycles and elevated temperature. Results showed that the concrete mechanical properties improved when the limestone aggregate was replaced by 10% BR or RT but gradually curtailed at higher addition rates. Such results concorded with the density, water absorption and porosity measurements. Foamed concrete containing BR is more resistant (compared to RT) to drying shrinkage, freeze/thaw cycle, and heat exposure, which was ascribed to the relatively lower BR porosity that improves the concrete mechanical properties and durability. [ABSTRACT FROM AUTHOR]

The study focuses on synthesizing wollastonite using bypass and silica fume waste materials as starting materials. The novelty of this work is the utilization of temperature-induced forming technique for the synthesis of wollastonite. Bypass and silica fume are mixed with various CaO/SiO2 ratios and then cast and fired at temperatures ranging from 900 to 1200 °C. Rheological properties and zeta potential are characterized for the slurries to optimize the dispersant percentage. The fired samples' phase composition, structure properties, apparent porosity, linear shrinkage, and compressive strength are characterized. Results show that the sample with a CaO: SiO2 ratio of 1:1.45 is the optimum composition for forming mainly pure β-wollastonite at 1100 °C, which changed into pseudo-wollastonite at about 1150 °C. The best physical and mechanical properties are obtained at 1170 °C, including apparent porosity of 8%, bulk density of 2.2 g/cm3, linear shrinkage of 13%, and compressive strength of 40 MPa, which widens its ceramic applications. [ABSTRACT FROM AUTHOR]

Utilizing steel slag aggregate (SA) as a substitute for river sand in 3D concrete printing (3DCP) has emerged as a new technique as natural resources become increasingly scarce. This study investigates the feasibility of using steel slag (SS) as fine aggregate for 3DCP. Ninety mixtures with varying steel slag aggregate-to-cement ratios (SA/C), water-to-cement ratios (W/C), and silica fume (SF) contents were designed to study the workability and compressive strength of the 3D-printed concrete. Additionally, the actual components were printed to evaluate the printability of these mixtures. The experimental results indicate that it is feasible to fully employ SA in concrete for 3D printing. Mixtures with slump values ranging from 40 to 80 mm and slump flow values varying from 190 to 210 mm are recommended for 3D printing. The optimal mix is determined to have SA/C and W/C ratios of 1.0 and 0.51, respectively, and an SF content of 10% by cement weight. A statistical approach was utilized to construct the prediction models for slump and slump flow. Moreover, to predict the plastic failure of the 3D-printed concrete structure, the modified prediction model with an SA roughness coefficient of 4 was found to fit well with the experimental data. This research provides new insights into using eco-friendly materials for 3D concrete printing. [ABSTRACT FROM AUTHOR]

Foam concrete has been used in various real-life applications for decades. Simple manufacturing methods, lightweight, high flowability, easy transportability, and low cost make it a useful construction material. This study aims to develop foam concrete mixtures for various civil and geotechnical engineering applications, such as in-fill, wall backfill and soil replacement work. A blended binder mix containing cement, fly ash and silica fume was produced for this study. Its compressive strength performance was compared against conventional general purpose (GP) cement-based foam concrete. Polypropylene (PP) fibre was used for both mixtures and the effect of various percentages of foam content on the compressive strength was thoroughly investigated. Additionally, two types of foaming agents were used to examine their impact on density, strength and setting time. One foaming agent was conventional, whereas the second foaming agent type can be used to manufacture permeable foam concrete. Results indicate that an increase in foam content significantly decreases the strength; however, this reduction is higher in GP mixes than in blended mixes. Nevertheless, the GP mixes attained two times higher compressive strength than the blended mix's compressive strengths at any foam content. It was also found that the foaming agent associated with creating permeable foam concrete lost its strength (reduced by more than half), even though the density is comparable. The compressive stress–deformation behaviour showed that densification occurs in foam concrete due to its low density, and fibres contributed significantly to crack bridging. These two effects resulted in a long plateau in the compressive stress–strain behaviour of the fibre-reinforced foam concrete. [ABSTRACT FROM AUTHOR]

This study presents a proof‐of‐concept for a fully recyclable and sustainable composite structural supercapacitor. The fabricated device shows promising energy storage capabilities and mechanical strength. Generally, structural supercapacitors capacitance is considerably lower than non‐load‐bearing mono‐functional supercapacitors and are made via thermoset polymer electrolyte. Here, the device is fabricated using an optimized solid electrolyte composition of carbon aerogel modified carbon fibers, fumed silica, lithium salt, and a thermoplastic polymer matrix. The supercapacitor exhibits a high capacitance of 5225 mFg−1 (193 mFcm−2) at 1 mVs−1 scan rate and a large voltage window of 4 V. A simple dissolution/reprecipitation method is used to demonstrate the recycling feasibility, with minimal mechanical degradation (<10%) in the polymer matrix and no chemical structure changes in the electrolyte. This work establishes a promising ecologically‐sound structural energy storage technology with favorable performance compared to prior studies. Highlights: A proof‐of‐concept fully recyclable composite structural supercapacitor is made.Thermoplastic‐based robust polymer electrolytes are fabricated.Recycling via dissolution and re‐precipitation of components is demonstrated.Comparison to prior structural supercapacitors shows favorable performance. [ABSTRACT FROM AUTHOR]

Low‐field nuclear magnetic resonance is adopted in this paper for the study of the hydration process of early‐age pure and composite cement paste by monitoring the longitudinal relaxation time (T1) of water constrained in the paste. Based on the correlation between the changes of weighted average T1 and the hydration process of paste, the hydration process can be divided into four stages, i.e., initial period, dormant period, accelerated period, and steady period. The effect of water‐to‐cement ratio (w/c) and admixtures to hydration is discussed in detail. Compared to WC04, the weighted average T1 at the end of the dormant period increased by 4.79, 1.74, and 0.05 ms when 30% fly ash, 30% slag, and 10% silica fume were added, respectively. Based on experimental data and the Avrami–Erofeev equation, a hydration model for both pure and composite cement pastes is proposed, with a correlation that is higher than 0.96, which can describe the hydration process of paste well. [ABSTRACT FROM AUTHOR]

Fumed silica was functionalized by piperazine followed by the reaction with 2- naphthalenesulfonyl chloride to prepare Fumed-Si-Pr-Piperazine-Naphthalenesulfonyl chloride (Fumed-Si-Pr-PNS), which was characterized to demonstrate the effective attachment on the surface of fumed silica. The optical sensing ability of Fumed-Si-Pr-PNS was studied via diverse metal ions in H2O solution by photoluminescence spectroscopy. The results showed that Fumed-Si-Pr-PNS detected selectively Hg2+ ions. The prepared sensor showed almost high absorption at different pH for Hg ion. After drawing various diagrams, The detection limits were calculated at about 12.45 × 10-6 M for Hg2+. [ABSTRACT FROM AUTHOR]

The performance of ultra-high-performance concrete (UHPC) allows for the design and creation of thinner elements with superior overall durability. The compressive strength of UHPC is a value that can be reached after a certain period of time through a series of tests and cures. However, this value can be estimated by machine-learning methods. In this study, multilayer perceptron (MLP) and Stacking Regressor, an ensemble machine-learning models, is used to predict the compressive strength of high-performance concrete. Then, the ML model's performance is explained with a feature importance analysis and Shapley additive explanations (SHAPs), and the developed models are interpreted. The effect of using different random splits for the training and test sets has been investigated. It was observed that the stacking regressor, which combined the outputs of Extreme Gradient Boosting (XGBoost), Category Boosting (CatBoost), Light Gradient Boosting Machine (LightGBM), and Extra Trees regressors using random forest as the final estimator, performed significantly better than the MLP regressor. It was shown that the compressive strength was predicted by the stacking regressor with an average R2 score of 0.971 on the test set. On the other hand, the average R2 score of the MLP model was 0.909. The results of the SHAP analysis showed that the age of concrete and the amounts of silica fume, fiber, superplasticizer, cement, aggregate, and water have the greatest impact on the model predictions. [ABSTRACT FROM AUTHOR]

Herein, we present an elegant and simple method for significant improvement of eugenol water solubility using the polymers Soluplus® and Lutrol F 127 as carriers and spray drying as an encapsulation method. The formulations were optimized by adding myo-inositol—a sweetening agent—and Aerosil® 200 (colloidal, fumed silica)—an anticaking agent. The highest encapsulation efficiency of 97.9–98.2% was found for the samples containing 5% eugenol with respect to the mass of Soluplus®. The encapsulation efficiencies of the spray-dried samples with 15% eugenol are around 90%. Although lowering the yield, the addition of Lutrol F 127 results in a more regular particle shape and enhanced powder flowability. The presence of Aerosil® 200 and myo-inositol also improves the rheological powder properties. The obtained formulations can be used in various dosage forms like powders, granules, capsules, creams, and gels. [ABSTRACT FROM AUTHOR]

Silica fume (SF) is an essential component in ultra-high-performance concrete (UHPC) to compact the matrix, but the nucleus effect also causes rapid hydration, which results in high heat release and large shrinkage. In this paper, the carboxylic agents, including polyacrylic acid and polycarboxylate superplasticizer, were used to surface modify SF to adjust the activity to mitigate hydration at an early time and to promote continuous hydration for a long period. The surface and dispersion properties of modified SF (MSF), as well as the strength and pore structure of UHPC, were studied, and the stability of the modification was also investigated. The results demonstrated that, after treatment, the carboxylic groups were grafted on the SF surface, the dispersion of SF was improved due to the increased negative pentanal of the particle surface and the steric hindrance effect, the early hydration was delayed about 3–5 h, and the hydration heat release was also mitigated. The compressive strength of UHPC with MSF reached a maximum of 138.7 MPa at 3 days, which decreased about 3.7% more than the plain group, while flexural strength varied insignificantly. More pores and cracks were observed in the matrix with MSF, and the hydration degree was promoted with MSF addition. The grafted group on SF fell off under an alkali environment after 1 h. [ABSTRACT FROM AUTHOR]

In this paper, the possibility of utilising coarse recycled concrete aggregate (CRCA) obtained from a construction and demolition waste (CDW) plant in Delhi to make 60 MPa self-compacted concrete (SCC) was evaluated. The CRCA was used in as-collected condition and was not processed any further. The aggregate packing (bulk) density (APD) method was adopted to prepare the SCC-CRCA mixture in order to obtain an aggregate mixture exhibiting maximum bulk density/least void content (45%). In addition, SCC was made using aggregate mixtures in which the natural coarse aggregate (NCA) was replaced with CRCA at 0%, 20% and 100% of the total coarse aggregate content by weight. The cement, fly ash, silica fume and water were kept constant for all SCC mixtures. The effects of CRCA on the flow behaviour, mechanical strength, shrinkage characteristics and microstructure properties of SCC mixtures were evaluated. The test results indicated that SCC mixtures made with up to 45% CRCA replacement can be used for structural concrete, which is higher than that recommended in Indian (20%) and international specifications (35%) for traditionally vibrated (conventional) concrete. [ABSTRACT FROM AUTHOR]

In order to solve the problem of poor mixture performance of cold recycled bitumen emulsion mixtures (CRBEM) during service, the improvement effects of air voids, 15°C indirect tensile strength (ITS), and immersion ITS of CRBEM were evaluated under the synergistic action of functional admixtures such as silica fume, microbeads, and water-reducing admixture based on orthogonal testing. The optimal mixing scheme was selected by verifying the mixture performance of CRBEM with functional admixtures. The micromorphology of cold recycled bitumen emulsion mortar under the optimal mixing scheme of multicomponent filler was observed by scanning electron microscopy (SEM). The mortar morphology was analyzed and labeled. The results show that the maximum decrease of air voids of CRBEM with functional admixtures can reach 23.6%. The maximum increase of ITS and immersion ITS can reach 115% and 104%, respectively. When the stress ratio is 0.3, the fatigue life times of Groups 4 and 5 reach 49,495 and 48,772, respectively, which are 9.91 and 9.77 times higher than those of Group 1. Silica fume plays a leading role in multicomponent fillers. The synergistic effect of multiple admixtures in CRBEM is significantly better than that of single or double admixtures. The morphology of bitumen emulsion composite mortar under the optimal mixing scheme of a multicomponent filler is a three-dimensional dense skeleton structure. The multicomponent filler can effectively improve the size and length of the mortar crystal. The multicomponent filler adding method is recommended to improve the performance of CRBEM. The optimal mixing scheme of the multicomponent filler is 1.5% cement, 2.4% external water, 1.5% silica fume, 2.0% microbeads, and 0.5% water-reducing admixture. [ABSTRACT FROM AUTHOR]

The paper presents results regarding the possibility and effectiveness of carrying out the internal hydrophobization in cement-based materials with mineral additives such as granulated blast furnace slag, silica dust and silica fly ash. The obtained results indicate that effective internal hydrophobization by using triethoxyoctylsilane is achievable and provides protection against water by decreasing the capillary absorption of water in the material. However, it also affects the hydration process of the binder, which results in a reduction in the compressive strength of the material. [ABSTRACT FROM AUTHOR]

Considering the increasing need for optimal use of water resources, using types of waste water instead of part of the water for making concrete and also reducing the use of potable water in concrete is particularly important, especially in developing countries. Accordingly, this study aimed to investigate and reinforce using greywater as a potential alternative to mixing water in concrete. The specimens' fresh, hardened, and durable properties from 14 concrete mix designs containing six mixing water types, three natural zeolite levels (0, 10, and 20%), and two silica fume levels (0 and 8%) were tested to achieve that. Mixing waters in this study consisted of distilled water, raw greywater, diluted greywater (50% greywater, 50% distilled water), simulations of greywater's salt and organic pollutants, and synthetic greywater. The results showed that raw greywater reduced average compressive strength by 8%, while diluted greywater caused a 1.5% increase instead. Mixing water standards requirements were satisfied on both raw and diluted greywater cases. The results also showed that the impact of greywater on the durability properties of concrete was non-critical in most cases, while diluted greywater, even slightly (4%), improved bulk electrical resistance (RCPT). The test results of synthetic waters showed that reducing chemically active salts and/or organic pollution in greywater can effectively increase the performance of the produced concrete. Using 8% silica fume as cement replacement improved the compressive strength of greywater-made concrete by up to 16% and reduced the cracks and porosity of the specimens based on SEM images. On the other hand, using 20% natural zeolite as cement replacement increased surface (using Wenner probes) and bulk chloride ion penetration by 36 and 78%, respectively. Based on these results, silica fume and natural zeolite replacement are impressive tools to reinforce greywater-made green concrete so that it can properly rival and even replace regular concrete even when using more polluted greywater. Furthermore, these replacements can be great potential alternatives to wastewater dilution or treatments. [ABSTRACT FROM AUTHOR]

Higher strengths can be achieved using environmentally friendly geopolymer concrete (GPC). Granulated blast-furnace slag (GBFS) and silica fume (SF) were used together in high-strength GPC, and the GBFS + SF mixture was replaced with fly ash at total rates of 5, 10, and 15%. Recycled waste tire wires were added at rates of 1, 2, and 3% by weight. The samples were cured under ambient and oven conditions for 28 days and subsequently tested to characterize their compressive, flexural, and splitting tensile strengths. The test results indicated that adding waste tire wires significantly influenced the samples cured under ambient conditions, leading to a strength increment of up to 45 MPa—an improvement of approximately 50%. The oven-cured samples improved strength by approximately 21%, and the maximum compressive strength peaked at 65 MPa. This result can be used as a positive reference for high-strength concrete. The addition of 3% waste tire wire resulted in a flexural strength of 15 MPa in samples cured under ambient conditions and up to 23 MPa in those cured in an oven. The splitting tensile strength peaked at 16 MPa, which agrees with the bending strength. Scanning electron microscopy and energy-dispersive X-ray analysis were performed on these samples, and the results corroborated these findings, yielding robust supporting evidence for the obtained results. [ABSTRACT FROM AUTHOR]

Accurate prediction of tensile stresses in repair mortars is vital for the long-term durability of rehabilitated concrete structures. Existing analytical models are based on the material property theory and often struggle to capture the intricate and non-linear behavior exhibited by different mix types used in concrete. To address the limitation of existing models, neural networks were employed as a modelling approach for more robust and versatile predictions. The data used in developing the models was obtained from laboratory experiments. The input variables to the ANN model included: water content, cement, silica fume, superplasticizer, admixture, and age. Three distinct ANN-based models were developed based on: ordinary Portland cement, 10% silica fume as a partial replacement of cement and a combination of the two binder types. These models were evaluated using four performance metrics: coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE), and mean absolute percentage error (MAPE). When mortars with ordinary Portland cement was used as a binder, the R2, MAE, MAPE, and RMSE were 99.74%, 0.0808, 0.0397, and 0.0138, respectively. For mortars with 10% silica fume, the ANN model predicted restrained shrinkage stresses in mortars with R2, MAE, MAPE, and RMSE values of 99.25%, 0.0090, 0.0731, and 0.3161, respectively. When both binders were used, the R2, MAE, MAPE, and RMSE were 99.77%, 0.0093, 0.0804, and 0.1775, respectively. The application of neural networks for predicting restrained shrinkage stresses in repair mortars outperforms conventional models with enhanced accuracy and reliability. The developed ANN models serve as powerful tools for assessing and optimizing the performance of repair mortars, enabling more efficient and precise design strategies in concrete repair. [ABSTRACT FROM AUTHOR]

Copyright of Romanian Journal of Civil Engineering / Revista Română de Inginerie Civilă is the property of Matrix Rom and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The administration of waste from constructing-demolition and the reuse of industrial waste materials are the main focuses of the sustainability initiatives. There are economic and environmental benefits to using recycled concrete aggregates (RCA). Nevertheless, the RCA mixes' poor performance necessitates the addition of more enhanced substances. This study investigated the moisture resistance of asphaltic mixes that included RCA and silica fume (SF). Coarse aggregates were replaced with RCA at three different percentages 15%, 30%, and 45%, which were pre-treated by immersing it in acid with a concentration of 0.1 mol. for a duration of 24 hours. Then the mixes containing RCA were incorporated with various amounts of SF, with 3%, 6%, and 9% of the binder's weight. These mixes were used to measure the Marshall characteristics and evaluate moisture resistance using indirect tensile strength, compresive strength tests. A thermal camera was employed to assess the modified asphalt's homogeneity. The thermal images demonstrated that after 30 minutes of mixing SF at 160 ℃, the asphalt cement has been uniformly distributed SF particles, as evident by the colour convergence. The findings revealed that the addition of RCA to the asphalt mix increased TSR and IRS levels by 6.68% and 8.93%, respectively, at RCA 30% compared to the original mixture. Additionally, the inclusion of silica fume led to a rise in TSR and IRS until 6%, after which there was a drop, but the levels remained above the original mix. The use of 30% RCA ratio with 6% silica fume resulted in the highest improvement in TSR and IRS, with a rise of 13.72% and 14.13%, respectively. [ABSTRACT FROM AUTHOR]

A new and original dosing of alumina-silicate wastes in preparing mixture of the geopolymeric material is presented in this paper. Unlike the usual preponderant utilization of fly ash and ground blast furnace slag, the article adopted a major proportion of concrete waste from building demolition compared to the other two mentioned components, aiming at obtaining high strength geopolymers. The result of applying this new dosing in the material mixture activated with alkaline solution was increasing the compression and flexural resistance of the geopolymer, especially at earl age of curing (7 days). The experiment showed that by mixing 310-470 kg⋅m-3 of concrete waste from demolition, 230-254 kg⋅m-3 of fly ash, 102-120 kg⋅m-3 of blast furnace slag, and 4 kg⋅m-3 of silica fume, the best performing mechanical characteristics of the geopolymer can be obtained. The optimal values of denseness were between 1.64-2.04 g⋅cm-3 and those of heat conductance were between 0.218-0.306 W⋅m-1⋅K-1. [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.)