Low-Carbon Cementitious Solutions for Modern Civil Engineering: Experimental Analysis of Concrete Incorporating GGBS and Fly Ash as Partial Cement Replacements

Abstract

Rapid urbanization and the rising pace of infrastructure development have significantly increased the global demand for construction materials, particularly cement, which is recognized as a major contributor to carbon dioxide emissions. In light of growing environmental concerns, civil engineers and materials scientists are actively exploring sustainable alternatives that reduce the ecological impact of conventional concrete. One promising and widely studied strategy is the partial replacement of Ordinary Portland Cement (OPC) with supplementary cementitious materials like Ground Granulated Blast Furnace Slag (GGBS) and fly ash. These industrial by-products are abundant, cost-effective, and environmentally friendly, offering the dual benefits of waste valorization and improved concrete performance. Their use aligns with the broader objectives of sustainable development and the circular economy in the construction sector. This study presents a detailed experimental investigation aimed at evaluating the mechanical and durability performance of low-carbon concrete incorporating GGBS and fly ash as partial cement replacements. Various concrete mixes were prepared with different substitution levels 10%, 20%, 30%, 40% and assessed through standardized tests for compressive strength, split tensile strength, and flexural strength at curing intervals of 7, 14, and 28 days. These mechanical tests were complemented by durability assessments, including water absorption, sulfate resistance, and acid resistance evaluations, to determine the materials' suitability in aggressive environmental conditions. The mix designs followed established civil engineering practices, ensuring workability and uniformity across samples. The experimental findings indicate that a 30% replacement level provides the most favorable balance between strength and durability. However, higher substitution ratios, particularly at 40%, resulted in significantly enhanced chemical resistance, suggesting potential applications in corrosive or marine environments. Compared to traditional concrete, the GGBS and fly ash-based mixes exhibited not only improved structural behavior but also a substantial reduction in carbon emissions due to lower OPC content. These blends also showed enhanced microstructural integrity and lower porosity, contributing to their long-term stability. The reduction in OPC consumption directly supports efforts to lower the embodied carbon of construction materials, addressing both environmental and regulatory challenges in the sector. Furthermore, the successful incorporation of industrial waste into structural concrete demonstrates the practical viability of adopting green engineering practices on a large scale. This research affirms the potential of GGBS and fly ash as alternative cementitious materials, offering a durable, cost-effective, and sustainable solution for modern civil engineering infrastructure. The outcomes of this study can assist engineers, contractors, and policymakers in advancing eco-efficient concrete technologies without compromising on performance or structural reliability.

Keywords: Low-carbon concrete, GGBS, Fly ash, Sustainable construction, Cement replacement, Mechanical properties, Durability performance, Industrial by-products, Eco-efficient materials, Civil engineering infrastructure.