A concrete mixture formulation consisting of industrial wastes such as fly ash and gypsum from ceramic mold waste as partial replacements for cement was developed in this two-part study to lessen the carbon footprint from processing the conventional materials used in the construction industry. The first part aims to determine the optimum composition of the ternary binder (cement, fly ash and recycled gypsum) and the curing period (7, 28 and 90) that will provide the highest compressive strength for the casted concrete cylinders. The second part focuses on establishing the effective polypropylene fiber (PPF) dosage, utilizing the pre-optimized binder composition. The structural integrity of the concrete cylinders was evaluated through compressive strength and split tensile tests following water curing periods of 7, 28, and 90 days. Results from the initial mechanical tests revealed that the optimum ternary binder composition was C60-F37.5-G2.5 cured for 90 days. While fiber reinforcement typically has limited impact on compressive strength, the addition of 1.5% PPF yielded better long-term compressive strength development compared with other PPF dosages. For tensile strength, 0.5%-1% PPF achieved the highest values at 28 days, whereas 1.5% PPF provided the peak performance under prolonged curing at 90 days. This shift in behavior is attributed to the progressive increase in fiber-bridging effectiveness over time. Findings from these mechanical tests were supported by the results from X-Ray Diffraction (XRD) analysis and optical microscopy.

This study evaluates the efficacy of micromechanical homogenization techniques for estimating the effective elastic modulus of sustainable concrete containing fly ash and recycled gypsum. In the absence of direct experimental measurements, a multi-phase computational framework was developed to simulate the interactions among coarse aggregate, mortar, and the interfacial transition zone (ITZ). A two-phase homogenization model was first calibrated against ACI 318-19 elastic modulus predictions through a sensitivity analysis, achieving a relative error below 3% across all ternary concrete mixtures. Subsequently, a three-phase model incorporating a 30 μm ITZ was developed to provide a more realistic representation of the composite microstructure. While the inclusion of the ITZ slightly increased the prediction error for the control mix, it consistently improved agreement with ACI-based estimates for all fly ash–gypsum blends. Overall, the simulated elastic modulus values showed strong convergence with empirical predictions, demonstrating that the proposed framework consistently reproduces established empirical stiffness trends and provides a physically informed baseline for future experimental validation. These findings highlight the potential of micromechanical modeling as a practical, reliable tool for future parametric studies and experimental validation of elastic properties in sustainable concrete systems.

This study presents a calibration-oriented multi-phase micromechanical homogenization framework for estimating the elastic modulus of sustainable concrete containing fly ash and recycled gypsum. In the absence of direct experimental measurements, a computational framework was developed to simulate the interactions among coarse aggregate, mortar, and the interfacial transition zone (ITZ). A two-phase homogenization model was first calibrated against the ACI 318-19 elastic modulus relationship through a sensitivity analysis, achieving relative errors below 3% with respect to the ACI-based empirical reference. Subsequently, a three-phase model incorporating a $30\mathsf{\mu }\mathrm{m}$ ITZ was developed to explicitly account for the influence of the interfacial transition zone on the effective elastic modulus within the adopted modelling assumptions. While the inclusion of the ITZ slightly increased the prediction error for the control mix, it consistently improved agreement with the ACI-based reference for all fly ash–gypsum blends. In addition, comparison with experimentally reported elastic modulus values for similar SCM-modified concretes demonstrated that the predicted values were physically reasonable and generally consistent with published data. Overall, the proposed framework reproduced stiffness trends predicted by the ACI empirical relationship and provides a physically informed computational baseline for future experimental validation and parametric investigations of sustainable concrete systems.