Search Results (73)

The modification of cementitious binders using active mineral additives and nano-components represents a crucial pathway for developing high-performance, sustainable concrete composites. Nevertheless, unilateral modification of the matrix with highly reactive siliceous materials often leads to an undesirable increase in composite brittleness. This study investigates the synergistic effect of the concurrent application of nano-silica (NS), silica fume (SF), and Class F fly ash (FA) in ternary and quaternary binders, aimed at optimizing both load-bearing capacity and fracture toughness. The experimental program was conducted on seven concrete series, evaluating their mechanical parameters and non-linear fracture properties using the two-parameter fracture model (TPFM) on notched beams subjected to three-point bending. Additionally, a high-resolution energy partitioning framework was applied, decomposing the total fracture energy into four distinct components—fracture initiation energy in the elastic range (G_ini), pre-peak microcracking energy (G_pre), main material softening energy (G_soft), and residual tail energy dissipated at large crack openings (G_tail)—along with the determination of the characteristic length (l_ch). The results demonstrated that while purely siliceous systems (modified with NS and SF) generate high strength increments, they simultaneously trigger a “brittleness trap,” manifested by a 13.65% decrease in the l_ch parameter. The introduction of FA effectively mitigates this hazard, transforming the failure mode into a quasi-ductile behavior. The concrete series modified with the NS+FA hybrid (Mix-5) exhibited a spectacular 107% increase in G_f and an increase in l_ch of nearly 50%, while maintaining high fracture toughness. Energy decomposition analysis in quaternary concretes confirmed a desirable reduction in the initiation energy share in favor of the softening and tail phases (G_tail reaching a record 13.1% for Mix-7), suggesting the probable activation of macroscopic crack-bridging mechanisms driven by the delayed hydration of FA particles. The research indicates that precise design of multi-component binders allows for achieving an optimal technological equilibrium point—the “sweet spot”—combining high structural capacity with safe material ductility. Full article

This study systematically investigated the durability of low-carbon concrete under severe service conditions using industrial solid wastes. The mechanical properties and carbonation resistance (including carbonation depth, compressive strength after carbonation, and splitting tensile strength after carbonation) were tested. Multi-scale characterization techniques, including XRD, SEM-EDS, and nanoindentation, were employed to investigate the microstructure. This approach revealed a synergistic mechanism linking microstructural evolution to the concrete’s macroscopic mechanical and durability performance. Results showed that incorporating 25% fly ash (FA) reduced compressive strength by 11.30% and 11.39% in CF-25 and BF-25 mixes, respectively, and increased carbonation depth by 58.46% in CF-25. In contrast, the addition of 5% silica fume (SF) produced different effects. It significantly enhanced the compressive strength of the CS-5 and BS-5 mixes by 18.92% and 9.94%, respectively. Furthermore, it improved the micromechanical properties of the interfacial transition zone (ITZ) and reduced its thickness. Micro-mechanistic analysis revealed that the low pozzolanic activity of FA at early ages led to insufficient hydration products, higher porosity, and a weaker ITZ. Conversely, SF, through its high pozzolanic reactivity and nano-filling effect, promoted a dense, highly polymerized gel structure and optimized pore size distribution. The distinct chemical characteristics of high-calcium and low-calcium cementitious systems further amplified the differential effects of these supplementary materials. Full article

Superhydrophobic photothermal coatings have great potential in anti-icing and de-icing applications. However, how to construct superhydrophobic coatings with high photothermal conversion performance and an appropriate rough structure is still a challenge. In this study, we first constructed the photothermal nanosphere coating by in situ co-deposition of tannic acid (TA) and (3-aminopropyl) triethoxysilane (APTES) and then by the coordination of iron ions (Fe³⁺). A superhydrophobic photothermal coating with a micro–nano–nano hierarchical rough structure was constructed by further applying a polydimethylsiloxane (PDMS)/hydrophobic fumed silica (SiO₂) coating. The coating has excellent superhydrophobic (water contact angle (WCA) of 158°) and efficient photothermal conversion performance (75 °C). Based on this, the coated fabric shows ideal performance in passive anti-icing and active de-icing tests. At the same time, the coated fabric also has an ideal UV shielding effect, which can ensure the long-term and efficient operation of the coated fabric in the outdoor sunlight. This preparation strategy provides an innovative method for the development of superhydrophobic photothermal coating materials and has broad application prospects in the field of flexible anti-/de-icing applications. Full article

Recycled aggregates (RAs) from construction and demolition waste (CDW) provide substantial circular-economy benefits, yet their elevated porosity, adhered mortar, and heterogeneity typically impair the mechanical performance and durability of recycled aggregate concrete (RAC). This PRISMA 2020-compliant systematic review synthesises 2180 records (2015–2026) to evaluate advanced strategies for enhancing RA quality prior to structural use. This paper critically compares removal-based treatments (mechanical, thermal, acid cleaning) with strengthening and densification approaches, including accelerated carbonation, pozzolanic and nano-silica coatings, polymer impregnation, microbial-induced calcium carbonate precipitation (MICP), and modified mixing methods such as triple-stage mixing (TSMA). Evidence shows that while all RA types (including recycled fine aggregate (RFA), recycled coarse aggregate (RCA), and their combination (RFCA)) can slightly reduce compressive strength and 30% replacement serves as a critical threshold, beyond this, strength loss accelerates, particularly in RCA and RFCA mixes. However, accelerated carbonation and TSMA consistently refine the interfacial transition zone, reduce water absorption by 17–30%, and recover 85–94% of natural aggregate concrete strength. Bio-deposition reduces water absorption by 13–21%, while acid/silica fume treatments improve late-age strength but carry environmental trade-offs. This review formulates a practice-oriented implementation framework for structural-grade RAC. Sustainability analyses indicate that carbonated RA can achieve net-positive CO₂ abatement when under low-carbon energy supply. A mechanistic schematic is presented to synthesise treatment-to-pore-structure/durability pathways across the four principal treatment routes, and a quantitative synthesis plot compares water absorption reductions across all treatment types using 13 data points drawn from included studies. A structured treatment comparison evaluates the energy intensity, industrial scalability, CO₂ footprint, and technology readiness level for each strategy. The remaining challenges include a lack of hybrid treatment studies, limited real-scale durability data, and insufficient mechanistic models linking treatment to pore structure evolution. This review recommends harmonised durability-based criteria and updates to standards (e.g., BS 8500, EN 12620) to support the scalable deployment of treated RA. Full article

The development of all-concrete liquefied natural gas (LNG) storage tanks is hindered by the susceptibility of conventional concrete to ultra-low temperature (ULT) cycling down to −70 °C. While redispersible polymer powder (RPP) and polypropylene (PP) fibers individually enhance performance, their combined effect in various mineral admixture systems remains unclear. This study investigates the synergy and selective compatibility in hybrid-modified concrete containing fly ash (FA), silica fume (SF), or slag (SG). Comprehensive assessments after 50 ULT cycles reveal that the efficacy of hybrid modification is intrinsically governed by the mineral admixture. Among all systems, the silica fume-based hybrid system (EPSF) exhibits the highest residual compressive strength (57.5 MPa), the lowest strength loss (6.7%), and the most balanced durability. Microstructural analysis reveals that this synergy arises from a dense matrix, continuous polymer network, and effective fiber bridging—achieved only when the mineral admixture enables uniform RPP distribution. In contrast, the FA system exhibits a strength–durability trade-off, with RPP localized at interfaces, while the SG system shows a polymer-activated hydration mechanism. Microstructural and nano-mechanical analyses confirm that RPP acts as a pore filler in cement, an interfacial modifier in FA, a cohesive network former in SF, and a hydration activator in SG. This work establishes that superior ULT resilience requires not merely additive modifications but a matrix-enabled synergy, providing a scientific basis for the rational design of cryogenic concrete. Full article

To investigate the influence patterns and underlying mechanisms of solid waste-derived Nano-Micro-Powder (NMP) materials on asphalt performance, this study selected nano-sized silica fume (a typical industrial solid waste) along with conventionally used hydrated lime and cement powders as representative modifiers. Based on material type, dosage, and particle size, the high-temperature rheological properties, low-temperature rheological behavior, and nano-scale mechanical characteristics of NMP-modified asphalt were systematically evaluated through dynamic shear frequency tests, Multiple Stress Creep Recovery (MSCR) tests, Bending Beam Rheometer (BBR) tests, and Atomic Force Microscopy (AFM) measurements. Additionally, the grey relational analysis method was employed to quantify the impact of key nanoparticle characteristics on modified asphalt performance. The results demonstrate the following: (1) With increasing NMP dosage and decreasing particle size, the complex modulus (G*) of modified asphalt increases significantly, while the creep recovery rate (R) rises and non-recoverable creep compliance (J_nr) decreases. The creep stiffness slope (m-value) diminishes under low-temperature conditions. (2) Among different NMP types, silica fume-modified asphalt exhibits the highest G*, R, and m-value parameters. (3) At the nanoscale, adhesion force, modulus, and surface roughness all increase with higher NMP dosage and smaller particle size. Silica fume demonstrates superior performance in these nano-mechanical properties compared to hydrated lime and cement powders. (4) Grey relational analysis reveals that specific surface area shows the strongest correlation with the overall performance of NMP-modified asphalt. Full article

As a key connection technology in prefabricated buildings, offshore wind power, and bridge engineering, the performance and environmental sustainability of grouted sleeve connections are essential for the long-term development of civil infrastructure. To address the environmental burden of conventional high-strength cement-based grouts, an eco-friendly sleeve grouting material incorporating industrial solid waste was developed. In this study, silica fume (15%) and fly ash (5%) were employed as supplementary cementitious materials, while nanosilica (NS) was introduced to enhance the material properties. Mechanical testing, microstructural characterization, and half-grouted sleeve uniaxial tensile tests were conducted to systematically evaluate the effect of NS content on grout performance. Results indicate that the incorporation of NS significantly accelerates the hydration of silica fume and fly ash. At an optimal dosage of 0.4%, the 28-day compressive strength reached 105.5 MPa, representing a 37.9% increase compared with the control group without NS. In sleeve tensile tests, specimens with NS exhibited reinforcement necking failure, and the load–displacement response closely aligned with the stress–strain behavior of the reinforcement. A linear relationship was observed between sleeve wall strain and reinforcement stress, confirming the cooperative load-bearing behavior between the grout and the sleeve. These findings provide theoretical guidance and technical support for developing high-strength, low-impact grouting materials suitable for sustainable engineering applications. 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

Cement-based materials are essential in modern construction, valued for their versatility and performance. Rheological properties, including yield stress, plastic viscosity, and thixotropy, play indispensable roles in optimizing the workability, stability, and overall performance of cement composites. This review explores the effects of supplementary cementitious materials (SCMs), chemical admixtures, nanomaterials, and internal curing agents on modulating rheological properties. Specifically, SCMs, including fly ash (FA), ground granulated blast furnace slag (GGBFS), and silica fume (SF), generally improve the rheology of concrete while reducing the cement content and CO₂ emissions. Regarding chemical admixtures, like superplasticizers (SPs), viscosity-modifying agents (VMAs), setting-time control agents, and superabsorbent polymers (SAPs), they further optimize flow and cohesion, addressing issues such as segregation and early-age shrinkage. Nanomaterials, including nano-silica (NS) and graphene oxide (GO), can enhance viscosity and mechanical properties at the microstructural level. By integrating these materials above, it can tailor concrete for specific applications, thereby improving both performance and sustainability. This review presents a comprehensive synthesis of recent literature, utilizing both qualitative and quantitative methods to assess the impacts of various additives on the rheological properties of cement-based materials. It underscores the pivotal roles of rheological properties in optimizing the workability, stability, and overall performance of cement composites. The review further explores the influences of SCMs, chemical admixtures, nanomaterials, and internal curing agents on rheological modulation. Through the strategic integration of these materials, it is possible to enhance both the performance and sustainability of cement composites, ultimately reducing carbon emissions and advancing the development of eco-friendly construction materials. Full article

Enhancing concrete’s resilience against freeze–thaw (F-T) cycles is a critical challenge in civil engineering, especially in cold climates, where repeated freezing and thawing lead to structural degradation. This review explores the effectiveness of various additives, including supplementary cementitious materials (SCMs) and chemical admixtures, in improving concrete durability under F-T conditions. Factors influencing F-T resistance include the type and percentage of SCM replacement, the water–cement ratio, pore structure refinement, and air entrainment. The mechanisms by which additives enhance the durability—such as reducing the permeability, improving the microstructure, and increasing the compressive strength—are examined through an extensive review of experimental studies. The findings indicate that manufactured additives, such as silica fume, metakaolin, nano-SiO₂, and graphene oxide, significantly enhance the F-T durability by densifying the concrete matrix and mitigating internal damage. In contrast, natural additives, including rice husk ash and zeolite, show potential but require optimization to match the performance of industrial SCMs. Additionally, the preparation and treatment methods of these materials play a crucial role in their effectiveness. This review provides insights into optimizing concrete formulations to enhance the longevity and sustainability, offering practical recommendations for the use of SCMs in cold climates. Full article

In this study, various raw materials, including silica sand, silica fume, calcium hydroxide, α-alumina, and nano-activated alumina, were used to produce hydroceramic systems with varying Ca/Si/Al ratios to optimize their high-temperature resistance. The hydroceramic slurries, with a constant density of 1.65 g/cm³, were all designed to have a setting time of more than 4 h at the condition of 240 °C and 50 MPa and then cured at the same condition for 2, 30, and 90 days to evaluate their long-term performances. Subsequently, compressive strength, water permeability, mercury intrusion porosimetry, thermogravimetry, and X-ray diffraction tests were conducted on set samples at various curing times to analyze the hydroceramic systems’ long-term stability and the underlying mechanism. The results indicated that the hydration reaction of α-Al₂O₃ was minimal, and its inclusion reduced the incorporation of silica sand in the hydration process. Nano-activated alumina improved the macroscopic properties of the hydroceramic systems and promoted the formation of a significant amount of tobermorite 11 Å. The addition of silica fume can enhance the system’s macroscopic properties and the long-term stability, promoting the reaction of silica sand. The long-term stability of slurries with a Ca/Si ratio of 1 was significantly better than that of slurries with a Ca/Si ratio of 0.5. The best-performing slurry can maintain a compressive strength of more than 19 MPa after being cured at 240 °C for 90 days. Full article

The main objective of this study is to reduce CO₂ emissions resulting from rapidly increasing cement production and utilization rates worldwide. For this purpose, the effects of NS (nano-silica) and SF (silica fume) materials, which are the post-production wastes of industrial products, the substitute material obtained by grinding SG (silica gel) wastes used for packaging purposes in the preservation of industrial electronic products and many other areas, and MLS (micritic limestone) obtained by grinding limestone, a natural resource, on mortars after cement substitutions were evaluated. MLS and SG contents were sieved through a 0.063 mm sieve and substituted into the mixtures, while specific surface area values for SF and NS were obtained as 23 m²/g and 150 m²/g. Each of these materials was used in mortars by substituting between 0% and 10% cement by weight. The samples were subjected to consistency determination and then evaluated for setting time. Subsequently, flexural tests were carried out on 40 mm × 40 mm × 160 mm specimens placed in molds, and compressive tests were carried out on prism fragments broken after flexural tests. The experimental results showed that substitution of SG substitutes with cement at 3–10 wt% was highly effective against SF, NS and MLS in terms of strength and workability properties. Full article

Silica fume (SF) has been widely used in engineering; however, its densification during transportation reduces its original pozzolanic activity. This paper investigates the effects of wet grinding and chemical activation on the mechanical properties and hydration products of silica fume in cement-based materials, revealing the mechanism by which wet grinding improves these properties. The results indicate that wet grinding effectively reduces the particle size of silica fume. Under optimal excitation conditions (250 r/min, 20 min), the median particle size is reduced to 12.1 μm, 2.27 times smaller than before excitation. The 28-day compressive strength of the silica fume cement paste reaches 60.8 MPa, 23.7% higher than that of the reference group. This approach effectively mitigates nano-agglomeration, enhances the pozzolanic activity of silica fume, and promotes AFt and C-S-H gel formation. The findings demonstrate that wet grinding activation can further enhance the utilization rate of silica fume. Full article

This research provides a comparative analysis of the optimization of ultra-high-performance concrete (UHPC) using artificial neural network (ANN) and response surface methodology (RSM). By using ANN and RSM, the yield of UHPC was modeled and optimized as a function of 22 independent variables, including cement content, cement compressive strength, cement type, cement strength class, fly-ash, slag, silica-fume, nano-silica, limestone powder, sand, coarse aggregates, maximum aggregate size, quartz powder, water, super-plasticizers, polystyrene fiber, polystyrene fiber diameter, polystyrene fiber length, steel fiber content, steel fiber diameter, steel fiber length, and curing time. Two statistical parameters were examined based on their modeling, i.e., determination coefficient (R²) and mean square error (MSE). ANN and RSM were evaluated for their predictive and generalization capabilities using a different dataset from previously published research. Results show that RSM is computationally efficient and easy to interpret, whereas ANN is more accurate at predicting UHPC characteristics due to its nonlinear interactions. Results show that the ANN model (R = 0.95 and R² = 0.91) and RSM model (R = 0.94, and R² = 0.90) can predict UHPC compressive strength. The prediction error for optimal yield using an ANN and RSM was 3.5% and 7%, respectively. According to the ANN model’s sensitivity analysis, cement and water have a significant impact on compressive strength. Full article

In today’s digital age, innovative artificial intelligence (AI) methodologies, notably machine learning (ML) approaches, are increasingly favored for their superior accuracy in anticipating the characteristics of cementitious composites compared to typical regression models. The main focus of current research work is to improve knowledge regarding application of one of the new ML techniques, i.e., gene expression programming (GEP), to anticipate the ultra-high-performance concrete (UHPC) properties, such as flowability, flexural strength (FS), compressive strength (CS), and porosity. In addition, the process of training a model that predicts the intended outcome values when the associated inputs are provided generates the graphical user interface (GUI). Moreover, the reported ML models that have been created for the aforementioned UHPC characteristics are simple and have limited input parameters. Therefore, the purpose of this study is to predict the UHPC characteristics while taking into account a wide range of input factors (i.e., 21) and use a GUI to assess how these parameters affect the UHPC properties. This input parameters includes the diameter of steel and polystyrene fibers (µm and mm), the length of the fibers (mm), the maximum size of the aggregate particles (mm), the type of cement, its strength class, and its compressive strength (MPa) type, the contents of steel and polystyrene fibers (%), and the amount of water (kg/m³). In addition, it includes fly ash, silica fume, slag, nano-silica, quartz powder, limestone powder, sand, coarse aggregates, and super-plasticizers, with all measurements in kg/m³. The outcomes of the current research reveal that the GEP technique is successful in accurately predicting UHPC characteristics. The obtained R², i.e., determination coefficients, from the GEP model are 0.94, 0.95, 0.93, and 0.94 for UHPC flowability, CS, FS, and porosity, respectively. Thus, this research utilizes GEP and GUI to accurately forecast the characteristics of UHPC and to comprehend the influence of its input factors, simplifying the procedure and offering valuable instruments for the practical application of the model’s capabilities within the domain of civil engineering. Full article