As modern civil engineering demands increasingly higher strength, toughness, and long-term stability from concrete materials, the performance limitations of ordinary concrete in complex service environments have become increasingly apparent. The dual-blending modification of nanomaterials and steel fibers (SF) has emerged as an effective technical approach to overcome these limitations. The ratio design of the TiC-NC-SF dual-blending system has largely relied on empirical methods, lacking systematic quantitative optimization. The synergistic mechanisms among multiple factors remain unclear, hindering the engineering application of modified concrete. This study employs Box-Behnken experimental design and response surface methodology to systematically investigate the influence patterns of three factors on concrete's 28-day compressive strength, splitting tensile strength, and flexural strength. Scanning electron microscopy (SEM) characterization reveals microstructural mechanisms, while model optimization validates optimal ratios. Results indicate the dominance order of the three factors on concrete mechanical properties is SF > NC > TiC (with NC and TiC having similar effects on compressive strength). A significant synergistic enhancement effect exists between TiC and NC (interaction term P < 0.05). Both TiC and NC enhance concrete strength by optimizing matrix density through "hydration regulation and multi-level filling," while SF dominates crack control via "bridging crack propagation and energy dissipation toughening." No significant interaction was observed between TiC-SF or NC-SF (P > 0.05). Concrete compressive strength exhibits a quadratic variation with increasing dosage of all three factors, with SF exerting greater influence on splitting tensile strength and flexural strength. The response surface model optimization yielded the optimal mix design of TiC 2.12%, NC 2.14%, and SF 1.19%. Its 28-day compressive strength, splitting strength, and flexural strength reached 69.83 MPa, 7.22 MPa, and 9.34 MPa, respectively (measured values). The response surface optimization values were 70.50 MPa, 7.52 MPa, and 9.60 MPa, respectively. According to the experimental results, these values increased by 22.66%, 26.44%, and 15.02%, respectively, compared with the control group (CG). The performance deviation from the optimal experimental group was less than 0.5%, and the deviation from the optimization target was within 10%. SEM characterization revealed that the cement matrix in the CN10 and CN18 groups exhibited significantly higher densification than the CG group, with SF tightly bonded to the matrix interface.
As modern civil engineering places increasing demands on concrete materials for high performance and environmental sustainability, the limitations of ordinary concrete in terms of resource consumption and performance enhancement have become increasingly apparent. Currently, the mix design of composite systems incorporating graphite tailings (GT), nanosilica (NS), and steel fibers relies heavily on empirical methods, lacks systematic quantitative optimization, and the mechanisms of synergy among these factors remain unclear, thereby limiting the engineering application of modified eco-concrete. This study employs a Box-Behnken design to systematically investigate the effects of GT, NS, and steel fibers on the 28-day compressive, split tensile, and flexural strengths of concrete. Combined with scanning electron microscopy (SEM) characterization to reveal the microstructural mechanisms, the study verifies the optimal mix proportions through model optimization. The results indicate that the effects of all three factors on the mechanical properties of concrete follow a quadratic nonlinear pattern. The strength of the main effects varies: for compressive strength, NS > steel fibers > GT; for split tensile and flexural strengths, steel fibers > NS > GT. Among these, steel fibers were the core dominant factor in enhancing the tensile and flexural properties of concrete (F-values of 1285.31 and 410.88, respectively). At the same time, NS was the dominant factor in improving compressive strength (F = 447.43), and the optimal replacement rate for graphite tailings was approximately 20%. Interaction analysis revealed significant synergistic effects between GT and NS for compressive strength, between NS and steel fibers for split tensile strength, and between GT and NS as well as NS and steel fibers for flexural strength (interaction terms P < 0.05). The comprehensive optimal mix ratio obtained through response surface model optimization was GT 21.79%, NS 1.48%, and steel fibers 1.49%. The measured 28-day compressive, split tensile, and flexural strengths reached 58.43 MPa, 6.74 MPa, and 10.82 MPa, respectively. Compared to the reference group, these values increased by 38.43%, 39.54%, and 44.65%, respectively, with the relative errors between the measured values and the model predictions all controlled within 5%. SEM characterization revealed that the cement matrix in the GNS4 and GNS18 groups exhibited significantly higher densification than the reference group. The transition zone at the interface between the steel fibers and the matrix exhibited tight bonding, providing reliable mechanical interlocking and chemical bonding that effectively suppressed crack initiation and propagation.
Ke Li, Guanzhe Fa· Frontiers in Materials· 0 citations
High-Early-Strength Concrete (HESC) is increasingly required in accelerated construction, yet most existing studies focus on single nano-additives rather than hybrid waste-derived systems. This study investigates the individual and combined effects of nanoclay (NC), nanosilica (NS), and cellulose nanofibers (NCel)—each produced from industrial or agricultural waste—on the mechanical and microstructural properties of HESC. A Box–Behnken response surface methodology (RSM) design was employed to optimize nanomaterial dosages with respect to early-age compressive strength, while microstructural evaluation (SEM, EDS, elemental mapping) clarified the mechanisms of enhancement. The results demonstrate that NC, NS, and NCel play complementary roles in hydration acceleration, particle packing, pore refinement, and crack-bridging. The optimized hybrid system (1.64% NC, 0.115% NS, 0.027% NCel) achieved a 3-day compressive strength of 59.7 MPa, 7-day strength of 71.2 MPa, and 28-day strength of 94.6 MPa, representing increases of 42.14%, 36.92%, and 21.59%, respectively, over the control mixture. Microstructural observations confirmed matrix densification, reduced Ca/Si ratio (from 2.05 to 1.68), refined pore structure (<0.4 μm vs. 0.9–1.2 μm in control), and enhanced ITZ in the optimized mixtures. Statistical analysis yielded robust predictive models (R2 = 0.977–0.996) with significant interaction terms confirming synergistic effects among the three nanomaterials. This work demonstrates that waste-derived hybrid nano-systems offer a sustainable and effective strategy for producing high-performance HESC, with the RSM-derived optimum providing balanced early- and later-age strength while maintaining practical feasibility for field implementation.
Nehal Hamed, Mohamed K. Ismail, M. Serag et al.· Sustainability· 0 citations
Recycled aggregate concrete (RAC) offers an effective approach to reducing the environmental burden associated with construction and demolition waste. In this study, a fiber-reinforced RAC was developed by replacing part of the cement with fly ash and ground granulated blast-furnace slag, while glass fibers or basalt fibers were incorporated as reinforcing materials. A systematic experimental program was conducted to evaluate the mechanical behavior of the proposed concrete under different saturation conditions. The results show that the best toughness performance was achieved in the natural moisture state. In comparison, compressive and flexural strengths reached their maximum values under dry conditions, whereas splitting tensile strength peaked in the natural state. Based on the experimental data, prediction equations were established for the splitting tensile and flexural strengths by considering both saturation degree and fiber content. A stress–strain model under uniaxial compression was also developed. In addition, scanning electron microscopy (SEM) was employed to examine the fiber–matrix interface and hydration products, thereby clarifying the microstructural characteristics of the concrete at different saturation levels.
Jie Zhou, Tengfei Guo, Xiang Li et al.· Buildings· 0 citations
Hybrid polymer composites reinforced with industrial waste materials and high-performance fibers have emerged as promising candidates for lightweight structural applications due to their enhanced mechanical performance, improved wear resistance, and sustainable material utilization. This study investigates the influence of fly ash (FA) and short carbon fiber (CF) reinforcement on the mechanical, thermal, and tribological behavior of epoxy composites. Composite laminates containing varying fly ash contents (0–12 wt.%) and carbon fiber contents (0–10 wt.%) were fabricated using the hand lay-up technique followed by compression molding to minimize void formation and improve interfacial bonding. Tensile, flexural, compressive, hardness, impact, and wear tests were conducted according to ASTM standards. Thermal stability was evaluated using thermogravimetric analysis (TGA), while fracture morphology was analyzed using scanning electron microscopy (SEM). Multi-objective optimization based on the Taguchi method and Grey Relational Analysis (GRA) was employed to determine the optimal reinforcement combination. The illustrative results indicate that the hybrid composite containing intermediate fly ash and carbon fiber contents provides the most balanced mechanical and tribological performance. The tensile strength, flexural strength, and wear resistance show considerable improvement compared with the neat epoxy system, whereas excessive fly ash loading results in particle agglomeration and localized stress concentration. SEM observations reveal improved matrix–reinforcement adhesion and reduced fiber pull-out in the optimized composite. These findings demonstrate the potential of fly ash/carbon fiber reinforced epoxy composites for lightweight automotive, aerospace, and engineering applications while promoting sustainable utilization of industrial waste.
N. M, K. B, V. M.· International Journal For Mu...· 0 citations
This study presents a comprehensive experimental investigation and multi-objective optimization of Hybrid Steel–Shape Memory Alloy Fiber Reinforced Concrete (HS–SMA FRC) designed to enhance mechanical performance and material efficiency. M40-grade concrete mixes incorporating steel fibers, NiTi-based SMA fibers, and hybrid combinations at volume fractions of 0.5% and 0.75% were evaluated. Mechanical properties, including compressive strength, split tensile strength, flexural strength, bond strength, and modulus of elasticity, were assessed at 7 and 28 days. The results indicate that hybrid fiber systems outperform mono-fiber and control mixes, with the 0.75% HS–SMA FRC mix achieving the highest compressive strength (64.25 MPa), split tensile strength (10.80 MPa), and flexural strength (12.5 MPa), attributed to synergistic crack-bridging and stress redistribution mechanisms. Microstructural observations using SEM and EDS suggest improved fiber–matrix bonding and a denser interfacial transition zone, supporting the observed mechanical enhancements. A hybrid optimization framework combining Response Surface Methodology (RSM) and NSGA-III was implemented to identify optimal trade-offs among performance parameters, with model-predicted results indicating efficient material configurations. However, the findings are limited to material-level behavior under monotonic loading conditions, and the optimization results are not experimentally validated. The study provides a robust foundation for developing high-performance hybrid fiber reinforced concrete with potential applicability in advanced structural systems.
N. Meenalochani, Ankit Sodha, P. Mehta· Journal of engineering and a...· 0 citations
Substituting aluminosilicate pozzolans for cement offers a stable and environmentally sustainable mixture. The primary innovation lies in incorporating polypropylene and steel fibers into self-compacting mixtures to enhance mechanical properties and durability, coupled with artificial intelligence modeling (artificial neural networks and decision trees) for compressive strength prediction. This integrated experimental and computational methodology enables more precise optimization of mix designs.The methodology involved producing 16 mix designs with alkaline concentrations of 8 and 12 M, variations in pozzolan quantities, and fiber volumes (0.5 to 1% by volume). Samples underwent ambient and heat curing, with evaluations of fresh properties (slump flow, L-box, V-funnel), mechanical properties (compressive and tensile strength), water absorption, shrinkage, and microstructure (SEM and XRD). Modeling was performed using experimental data to predict compressive strength. Results indicated that increasing molarity from 8 to 12 densifies the concrete microstructure, boosting compressive strength by up to 25% (from 40 to 96.83 MPa at 28 days), although alkaline solution costs may rise. Steel fibers, by forming resilient internal networks, improved tensile and flexural strength by up to 30% and reduced drying shrinkage by 11% . Hybrid fiber combinations enhanced high-temperature durability, retaining 80% strength at 600°C. The AI models achieved accuracies exceeding 88% , positioning this concrete as a sustainable and efficient alternative to Portland cement concrete.
Meysam Rostami, Vahid Rostami, A. Lork· Journal of Resource Manageme...· 0 citations
