SUSTAINABLE MATERIALS CHARACTERIZATION FOR LOW-CARBON CONSTRUCTION AND INFRASTRUCTURE DURABILITY

Abstract

This quantitative study investigates the characterization of sustainable construction materials through a comprehensive framework integrating mechanical, microstructural, and environmental performance analyses. Designed as a randomized, controlled laboratory experiment within a partially nested 3×3×4 factorial arrangement, the research compares three binder systems—ordinary Portland cement (OPC), OPC blended with supplementary cementitious materials (SCMs), and alkali-activated/geopolymer binders under four exposure conditions: chloride, carbonation, sulfate, and freeze thaw environments. The study’s objective was to determine the extent to which binder composition, replacement ratio, and aggregate type influence material durability and embodied carbon, thereby establishing quantifiable pathways for low-carbon infrastructure development. Specimens were prepared using standardized casting and curing procedures, then evaluated for mechanical performance (compressive strength, tensile capacity, and elastic modulus), transport properties (chloride diffusion, carbonation depth, and water absorption), and environmental durability (freeze–thaw resistance and sulfate attack). Microstructural characterization via Scanning Electron Microscopy (SEM), Mercury Intrusion Porosimetry (MIP), and X-Ray Diffraction (XRD) quantified pore structure, phase composition, and hydration dynamics. Life Cycle Assessment (LCA), conducted per ISO 14040/44 standards, provided complementary data on embodied energy and CO₂ emissions, leading to the development of a Durability-Adjusted Carbon Index (DACI)a composite sustainability indicator that normalizes carbon performance by mechanical reliability. Data collection occurred at 7, 28, 90, and 180 days to capture both early-age and long-term trends, ensuring reproducibility and empirical robustness. The results demonstrated that SCM and geopolymer systems significantly outperformed traditional OPC concretes. Compressive strength improved by up to 25%, accompanied by a 50–70% reduction in chloride diffusion and carbonation rates. Embodied carbon declined from 410 kg CO₂-e/m³ for OPC to 195 kg CO₂-e/m³ for geopolymer concretes, while cumulative energy demand fell by nearly 30%. Correlation analyses revealed strong inverse relationships between porosity and compressive strength (r = −0.83, p < 0.01) and between chloride diffusion and DACI (r = −0.73, p < 0.01), confirming that denser microstructures not only enhance mechanical integrity but also reduce environmental degradation. Regression and mixed-effects modeling identified binder type and SCM ratio as dominant predictors of performance (β > 0.40, p < 0.001), with significant binder–exposure interactions indicating superior resilience of geopolymer mixes under carbonation and sulfate attack. Statistical validation confirmed high internal consistency (Cronbach’s α ≥ 0.87), excellent test–retest reliability (r > 0.90), and absence of multicollinearity (VIF < 4.0), ensuring methodological rigor.