The growing demand for concrete in tropical regions faces two unresolved challenges: the high carbon footprint of ordinary Portland cement (OPC) and limited understanding of how supplementary cementitious materials affect the mechanical performance of laterite rock aggregates concrete. Although metakaolin (MK) is a highly reactive pozzolan, its combined use with laterite rock aggregates concrete and its influence on strength development and microstructure have not been sufficiently clarified. This study investigates the mechanical behavior and sustainability potential of laterite rock aggregate concrete in which OPC is partially replaced by MK at 0%, 5%, 10%, 15%, and 20% by weight. All mixes were prepared at a constant water–binder ratio of 0.50 and tested for workability, compressive strength, split-tensile strength, and flexural strength at 7, 14, and 28 days, with and without a polycarboxylate-based superplasticizer. The results show that MK significantly enhances the mechanical performance of laterite rock concrete, with an optimum at 10% replacement: the 28-day compressive strength increased from 35.6 MPa (control) to 53.9 MPa in the superplasticized mix, accompanied by corresponding gains in tensile and flexural strengths. SEM–EDS analyses revealed microstructural densification, reduced portlandite, and a refined interfacial transition zone, explaining the improved strength and cracking resistance. From an environmental perspective, a 10% MK replacement corresponds to an approximate 10% reduction in clinker-related CO2 emissions, while the use of locally available laterite rock reduces the dependence on quarried granite and transportation impacts. The findings demonstrate that MK-modified laterite rock concrete is a viable and eco-efficient option for structural applications in tropical regions. The study concludes that MK-enhanced laterite rock aggregate concrete can deliver higher structural performance and improved sustainability without altering conventional mix design and curing practices.

The growing demand for sustainable road infrastructure has intensified the interest in alternative mineral fillers that reduce natural resource consumption and environmental impacts. This study investigates the use of Sugarcane Bagasse Ash (SBA), an abundant agricultural by-product in sub-Saharan Africa, as a partial replacement for conventional mineral fillers in hot-mix asphalt (HMA). Unlike previous studies that considered SBA primarily as a minor additive, this study provides a systematic evaluation across a wide replacement range (0–16 %), combined with experimental testing and numerical validation. Marshall and indirect tensile strength (ITS) tests were conducted on HMA mixtures produced using locally sourced Nigerian aggregates and 60/70 penetration-grade bitumen. A three-dimensional finite element model (FEM) of the ITS configuration was developed to corroborate the experimental response and identify stress concentration zones. results indicate that SBA improves both mechanical and volumetric performance within an optimal replacement range of 6–10 %, with peak performance of approximately 8 % SBA. Within this range, Marshall stability increased from 7.6 kN to 9.0 kN, the Marshall quotient reached 3.3 kN/mm, bulk density increased to 2.51 g/cm³, and air voids decreased from 4.9 % to 3.5 %, remaining within standard design limits. Microstructural analyses confirmed the predominance of amorphous silica and porous SBA morphology, which promoted enhanced filler–binder interactions and mixture densification. FEM predictions of peak tensile stress agreed with laboratory ITS results within 10 % and successfully reproduced observed crack initiation zones. Excessive SBA content (> 10 %) led to reduced stability and density owing to over-filling effects. The findings demonstrate that 6–10 % SBA is a technically viable and sustainable filler replacement for HMA, particularly in sugarcane-producing regions, offering improved performance alongside waste valorization and reduced reliance on quarry-derived fillers.

Accurate estimation of concrete compressive strength using non-destructive testing (NDT) methods remains challenging because widely used empirical correlations often neglect key mix design parameters, particularly the water–cement (w/c) ratio. This study investigates the influence of the w/c ratio on concrete compressive strength and on the predictive performance of combined rebound hammer (RH) and ultrasonic pulse velocity (UPV) models through controlled laboratory experiments using locally sourced Nigerian materials. Six concrete mixes with w/c ratios ranging from 0.45 to 0.70 were prepared with a constant 1:1:2 mix proportion and tested at curing ages of 7, 14, and 28 days. RH and UPV measurements were conducted on laboratory-cured cube specimens and correlated with compressive strength obtained from standard destructive tests. Pearson correlation analysis revealed strong positive relationships between compressive strength and RH (r = 0.96) and UPV (r = 0.93), while increasing w/c ratio consistently reduced both strength and NDT responses. A multivariate regression model incorporating RH, UPV, and curing age was developed to predict compressive strength across the investigated mixes. The model achieved a coefficient of determination (R²) of 0.79 with low prediction errors (RMSE = 1.46 MPa; MAE = 1.26 MPa). Comparative analysis showed that the proposed model outperformed single-parameter approaches and highlighted the limitations of generic SonReb correlations when applied without local calibration. The results demonstrate that reliable NDT-based strength prediction is strongly mix-sensitive and requires locally calibrated models for accurate laboratory-based quality control.