Search Results (114)

This article investigates the synergistic effect of metakaolin waste (MW) derived from the production of expanded glass granules and nano-silica (NS) on the hydration and other properties of ultra-high-performance concrete (UHPC) reinforced with steel fibres. The study focusses on cases where 5%, 10%, or 20% of cement is replaced with MW and 1% of NS is added. Various properties are evaluated, including the exothermic temperature, mineral composition (XRD), relative main compound quantities according to their decomposition (TG and DTG), shrinkage, density, and flexural and compressive strengths after 7 days, 28 days, and 2 years. In addition, changes in the concrete microstructure are analysed after 28 days and 2 years. The results demonstrate that the combined addition of MW and NS accelerates hydration by about 3 h compared to the control sample. The TG results confirmed a lower portlandite content due to the dilution effect of cement replacement. However, when both additives were used simultaneously, the portlandite content decreased further because of the intensified pozzolanic reaction, while the amount of C–S–H increased. Using MW and NS together significantly enhanced the long-term strength of concrete: after 2 years, the compressive strength of the mix with 5% of cement replaced by MW and 1% of NS was 182 MPa, compared to 146 MPa for the control sample. Full article

This study presents a systematic evaluation of frost resistance in concrete modified with nano-alumina (NA, 1 wt%), nano-silica (NS, 2 wt%), and polypropylene fiber (PP, 0.2 wt%) through accelerated freeze–thaw testing. The investigation employed a comparative experimental approach, subjecting specimens with optimal mechanical dosages to 300 freeze–thaw cycles. The degradation was quantitatively assessed by monitoring the evolution of mass loss, dynamic elastic modulus, and compressive strength. Results reveal that PP-modified concrete demonstrates optimal performance, retaining 70% of its dynamic elastic modulus (vs. 68% for NA and 64% for control, and failing at 58% for NS after 200 cycles) and exhibiting only 9.3% compressive strength loss (vs. 13.9% for NA and 27.3% for control, and 43.6% for NS). These findings establish PP as the most effective modifier, offering both superior frost resistance (300+ cycle durability) and practical advantages (simpler processing, lower cost). The results provide a scientific basis for designing high-performance concrete in cold regions, with particular relevance to infrastructure requiring long-term durability under cyclic freezing conditions. Full article

Cementitious materials are multiscale and multiphase composites whose frost resistance at the macroscale is closely governed by microstructural characteristics. However, the interfacial transition zone (ITZ) between clinker and hydrates, recognized as the weakest solid phase, plays a decisive role in the initiation and propagation of microcracks under freezing conditions. Understanding the frost damage mechanism of ITZ is therefore essential for improving the durability of concrete in cold regions. The motivation of this study lies in revealing how freezing affects the mechanical integrity and microstructure of ITZ in its early ages, which remains insufficiently understood in existing research. To address this, a nanoscratch technique was employed for its ability to quantify local fracture properties and interfacial adhesion at the submicronscale, providing a direct and high-resolution assessment of ITZ behavior under freeze–thaw action. The ITZ thickness and fracture properties were characterized in unfrozen cement paste and in cement paste frozen at 1 and 7 days of age to elucidate the microscale frost damage mechanism. Moreover, the enhancement effect of nano-silica modification on frozen ITZ was investigated through the combined use of nanoscratch and mercury intrusion porosimetry (MIP). The correlations among clinker particle size, ITZ thickness, and ITZ fracture properties were further established using nanoscratch coupled with scanning electron microscopy (SEM). This study provides a novel micromechanical insight into the frost deterioration of ITZ and demonstrates the innovative application of nanoscratch technology in characterizing freeze-induced damage in cementitious materials, offering theoretical guidance for designing durable concrete for cold environments. Full article

Nano-silica modified concrete (NSC) has been widely applied in engineering practice. However, conventional manual mix proportion design is both time-consuming and costly. In this study, four machine learning models—XGBoost, CatBoost, Random Forest, and AdaBoost—were trained to predict the compressive strength of NSC. Based on the best-performing model, the NSGA-II algorithm was employed to develop a multi-objective optimization framework, considering compressive strength, cost, and carbon emissions as objectives. The results indicated that XGBoost achieved the highest accuracy, with R² = 0.99 and RMSE = 1.80 MPa. Feature importance analysis further revealed that nano-silica content was strongly correlated with strength (0.82) and cost (0.85). Using NSGA-II, a set of Pareto-optimal solutions was generated. The NSGA-II algorithm produced Pareto-optimal solutions, highlighting the trade-offs among the three objectives. This integrated approach effectively reduces experimental workload and provides a valuable reference for sustainable NSC mix proportion design. Full article

In this study, the synergistic effects of a combination of nano additives (nano-clay (NC) and nano-silica (NS)) on the compressive strength (CS) of concrete exposed to temperatures ranging between 25 °C and 800 °C were modeled with two machine learning (ML) techniques: extreme gradient boosting (XGB) and random forest (RF) algorithms. A dataset comprising 169 compressive strength results (using four input parameters: NC dose, NS dose, temperature, and duration) was utilized for the raw data for the prediction models. The results indicated the superior performance of the XGB model in terms of the high accuracy attained in the prediction and the few errors present. Furthermore, SHAP analysis demonstrated that temperature has the highest negative impact on the prediction of the CS of nano-modified concrete. The individual conditional expectation (ICE) with partial dependence plots (PDPs) demonstrated that the optimum doses of NS and NC, leading to maximum compressive strength, were (2~3%) and (5~6%) by weight of cement. The developed models can be used as tools for optimizing mix designs to enhance fire resistance, thereby contributing to more durable and sustainable concrete construction and reducing the need for costly experimental trials. Full article

Nano-silica (NS) is used to enhance the mechanical and durability properties of cementitious materials; however, its frequent tendency to agglomerate limits its effectiveness and uniform distribution within the cement matrix. The main goal of this study was to improve NS dispersion and therefore to improve the properties of the concrete by coating NS onto standard sand particles (sand@NS) using the Stöber method, creating a composite material that acts as a filler, nucleation site, and highly reactive pozzolanic agent. The resulting sand@NS was incorporated into cement mixtures, and its compressive strength was measured after 3, 7, and 28 days of curing. In addition, water absorption and microstructural density were also evaluated. Comparative results showed that sand@NS significantly enhanced early-age hydration and initial strength, with a 145% increase in compressive strength at 28 days compared to the reference, whereas free NS resulted in a 120% increase. The early-age strength improvement was mainly due to the increased number of nucleation centers, while later strength gains were attributed to pozzolanic activity of the immobilized NS. Additionally, sand@NS reduced water absorption and increased microstructural density, even with reduced cement content, supporting more sustainable and eco-efficient concrete production. This work shows a promising, scalable, and cost-effective strategy to maximize the performance of NS in cementitious systems and supports its broader adoption in advanced construction materials. Full article

Achieving the close packing and interlocking of coarse aggregates in concrete enhances the elastic modulus, thereby reducing deformation, and can improve the overall stiffness of concrete structures. This study focuses on reinforcing and toughening concrete with close-packing aggregate with silica fume and micro-steel fibers, and investigates its durability properties, including long-term mechanical performance, water absorption, and sulfate erosion resistance under dry–wet cyclic exposure. The experimental results indicate that the 360-day long-term compressive strength of the concrete reaches up to 109.3 MPa, and the 360-day flexural strength reaches 11.62 MPa. The addition of silica fume effectively reduces the water absorption of concrete with close-packing aggregate and improves its sulfate erosion resistance under dry–wet cycles. The lowest 28-day water absorption rate is 2.41%, and after 150 cycles of sulfate erosion, the compressive strength corrosion resistance coefficient of the concrete can be maintained at up to 68.4%, while the sulfate erosion resistance grade reaches up to KS120. The concrete overall exhibits excellent durability properties. Moreover, this is beneficial for enhancing the concrete’s performance under dry–wet cycles and its resistance to the effects of sulfate attack. Full article

This study aims to investigate the mechanical behavior of cement mortar and concrete through a hybrid approach that integrates artificial intelligence (AI) techniques with finite element modeling (FEM). Support Vector Machine (SVM) models with Radial Basis Function (RBF) and polynomial kernels, along with Multilayer Perceptron (MLP) neural networks, were employed to predict the compressive strength (Fc) and flexural strength (Fs) of cement mortar incorporating nano-silica (NS) and micro-silica (MS). The dataset comprises 89 samples characterized by six input parameters: water-to-cement ratio (W/C), sand-to-cement ratio (S/C), nano-silica-to-cement ratio (NS/C), micro-silica-to-cement ratio (MS/C), and curing age. Simultaneously, the axial compressive behavior of C20-grade concrete was numerically simulated using the Concrete Damage Plasticity (CDP) model in ABAQUS, with stress–strain responses benchmarked against the analytical models proposed by Mander, Hognestad, and Kent–Park. Due to the inherent limitations of the finite element software, it was not possible to define material models incorporating NS and MS; therefore, the simulations were conducted using the mechanical properties of conventional concrete. The SVM-RBF model demonstrated the highest predictive accuracy with RMSE values of 0.163 (R² = 0.993) for Fs and 0.422 (R² = 0.999) for Fc, while the Mander model showed the best agreement with experimental results among the FEM approaches. The study demonstrates that both the SVM-RBF and CDP-based modeling approaches serve as robust and complementary tools for accurately predicting the mechanical performance of cementitious composites. Furthermore, this research addresses the limitations of conventional FEM in capturing the effects of NS and MS, as well as the existing gap in integrated AI-FEM frameworks for blended cement mortars. Full article

Modified sulfur cake is a by-product of sulfuric acid and hydrometallurgical processes, and presents an underutilized resource in sustainable infrastructure with significant potential. This review evaluates the current technological innovations as pertaining to the use of modified sulfur cake in the manufacture of sulfur concrete and sulfur-modified bitumen. The processing strategies (thermal, chemical, and mechano-chemical processing, and effects of organic and inorganic additives to promote mechanical, chemical, and thermal behaviors) are discussed systematically. The effect of the modified sulfur cake on the workability, compressive strength, corrosion resistance, and environmental resistance of construction materials, in particular, is tested, with compression strengths beyond 40 MPa being reported, alongside the improved rutting resistance up to 40%. The most critical limitations associated with phase instability, toxic gas release during processing, compositional variability, and the absence of standardization are identified. Correspondingly, to alleviate them, new developments such as blends with sulfur, nano-reinforcements (e.g., carbon nanotubes (CNT), nano-silica), and the incorporation of formulation optimization by machine-learning are considered. The review particularly focuses on the life cycle performance, reduction in volatile organic compounds (VOC) emissions, and circular economy advantages, highlighting modified sulfur cake as an economical and low-carbon alternative to conventional concrete and bitumen. This review mainly aims to bridge the gap between waste valorization and green construction technologies, offering a roadmap for future research and industrial implementation in line with global climate and sustainability goals. Full article

The interfacial transition zone (ITZ) significantly influences the mechanical properties and durability of lightweight aggregate concrete (LWAC), yet existing research on the ITZ in LWAC remains fragmented due to varied characterization techniques, inconsistent definitions of ITZ thickness and porosity, and the absence of standardized performance metrics. This review focuses primarily on structural LWAC produced with artificial and natural lightweight aggregates, with intended applications in high-performance civil engineering structures. This review systematically analyzes the microstructure, composition, and physical properties of the ITZ, including porosity, microhardness, and hydration product distribution. Quantitative data from recent studies are highlighted—for instance, incorporating 3% nano-silica increased ITZ bond strength by 134.12% at 3 days and 108.54% at 28 days, while using 10% metakaolin enhanced 28-day compressive strength by 24.6% and reduced chloride diffusion by 81.9%. The review categorizes current ITZ enhancement strategies such as mineral admixtures, nanomaterials, surface coatings, and aggregate pretreatment methods, evaluating their mechanisms, effectiveness, and limitations. By identifying key trends and research gaps—particularly the lack of predictive models and standardized characterization methods—this review aims to synthesize key findings and identify knowledge gaps to support future material design in LWAC. Full article

To address the mechanical deficiencies of traditional pervious concrete and promote its practical implementation, this study developed a high-performance pervious concrete model using conventional materials and methods, achieving a permeability coefficient of 4.5 mm/s with compressive and flexural strengths exceeding 45 MPa and 5 MPa, respectively. Central composite design (CCD) response surface methodology was employed to investigate the individual and synergistic effects of the water–cement ratio (W/C), nano-silica (NS), and carbon fibers (CF) on permeability, compressive strength, and flexural strength. Statistical models demonstrating prediction errors within 7% of experimental values were established, supplemented by a microstructural analysis of the concrete specimens. The results demonstrated that (1) the W/C ratio significantly influences overall performance; (2) NS enhances mechanical strength while reducing permeability, though excessive NS content induces weak interfacial zones that compromise strength; (3) CFs exhibit negligible impact on compressive strength but substantially improve flexural performance; and (4) significant synergistic interactions are present across W/C ratio, NS, and CFs concerning flexural strength parameters, while no significant interaction was observed for compressive strength. Full article

With the continuous improvement in technology, the construction industry is constantly advancing. Traditional concrete can no longer meet modern market demands, making research on new types of concrete imperative. This study reviews the application of common nanomaterials in concrete and their impact on concrete performance. It provides a detailed explanation of the characteristics of three common nanomaterials: nano-silica, nano-calcium carbonate, and carbon nanotubes. This study analyzes how these materials improve the microstructure, accelerate hydration reactions, and enhance interfacial transition zones, thereby enhancing the mechanical properties, durability, and workability of concrete. For conventional engineering projects, nano-calcium carbonate is the preferred choice owing to its low cost and its capacity to improve workability and early-age strength. For high-strength and durable structures, nano-silica is selected due to its high specific surface area (ranging from 100 to 800 m²/g) and its superior compactness and impermeability. In the context of intelligent buildings, carbon nanotubes are the most suitable option because of their exceptional thermal conductivity and electrical conductivity (with axial thermal conductivity reaching 2000–6000 W/m*K and electrical conductivity ranging from 10³ to 10⁶ S/cm). However, it should be noted that carbon nanotubes are the most expensive among the three materials. Additionally, this study discusses the issues and challenges currently faced by the application of nanomaterials in concrete and looks ahead to future research directions, aiming to provide a reference for further research and engineering applications of nanomaterials in the field of concrete. Full article

Guardrail concrete in cold regions frequently suffers from corrosion due to icing and solutions, significantly shortening the service life of the guardrail. This paper proposed a cement-based composite coating for concrete protection. The hydrophobic agent was synthesized using nano-silica, tetraethyl orthosilicate and perfluorodecyltrimethoxysilane and used for coating modification as an additive or by impregnation. Also, a commercial hydrophobic agent was used for comparison. The modified coating was characterized by wettability, mechanical properties, chemical stability and icephobicity tests. The results showed that the coating prepared with the synthetic hydrophobic agent presented a higher contact angle than that prepared with the commercial one during the above tests. Moreover, it featured excellent icephobicity by effectively delaying the time of icing on concrete and reducing the icing mass and ice adhesion strength. In addition, the hydrophobic agent used by impregnation was a better choice for concrete surface protection. Chemical composition and morphology analysis of the coating showed that hydrophobicity and icephobicity were mainly attributed to F-containing functional groups and rough structure with low surface energy. This study provided an application potential of modified cement-based composite coating for anti-/de-icing of guardrail concrete. Full article

The application of superhydrophobic (SH) coatings in road construction has attracted growing attention due to their potential to improve surface durability, reduce cracking, and enhance skid resistance. Among various materials, SiO₂ nanoparticles have emerged as key components in SH coatings by contributing essential surface roughness and hydrophobicity. This review paper analyzes the role of SiO₂ nanoparticles in enhancing the water-repellent properties of coatings applied to road surfaces, particularly concrete and asphalt. Emphasis is placed on their influence on road longevity, reduced maintenance, and overall performance under adverse weather conditions. Furthermore, this review compares functionalization techniques for SiO₂ using different hydrophobic modifiers, evaluating their efficiency, cost effectiveness, and scalability for large-scale infrastructure. In addition to highlighting recent advancements, this study discusses persistent challenges—including environmental compatibility, mechanical wear, and long-term durability—that must be addressed for practical implementation. By offering a critical assessment of current approaches and future prospects, this short review aims to guide the development of robust, high-performance SH coatings for sustainable road construction. Full article

Lightweight concrete (LWC) has emerged as a transformative material in sustainable and high-performance construction, driven by innovations in engineered lightweight aggregates, supplementary cementitious materials (SCMs), fiber reinforcements, and geopolymer binders. These advancements have enabled LWC to achieve compressive strengths surpassing 100 MPa while reducing density by up to 30% compared to conventional concrete. Fiber incorporation enhances flexural strength and fracture toughness by 20–40%, concurrently mitigating brittleness and improving ductility. The synergistic interaction between SCMs and lightweight aggregates optimizes matrix densification and interfacial transition zones, curtailing shrinkage and bolstering durability against chemical and environmental aggressors. Integration of recycled and bio-based aggregates substantially diminishes the embodied carbon footprint by approximately 40%—aligning LWC with circular economy principles. Nanomaterials such as nano-silica and carbon nanotubes augment early-age strength development by 25% and refine microstructural integrity. Thermal performance is markedly enhanced through advanced lightweight fillers, including expanded polystyrene and aerogels, achieving up to a 50% reduction in thermal conductivity, thereby facilitating energy-efficient building envelopes. Although challenges persist in cost and workability, the convergence of hybrid fiber systems, optimized mix designs, and sophisticated multi-scale modeling is expanding the applicability of LWC across demanding structural, marine, and prefabricated contexts. In essence, LWC’s holistic development embodies a paradigm shift toward resilient, low-carbon infrastructure, cementing its role as a pivotal material in the evolution of next-generation sustainable construction. Full article