Eco-efficient concrete using blast furnace slag

optimized performance, lower costs, reduced CO2eq emissions

Abstract

This study evaluated eco-efficient concretes with partial replacement of Portland cement by blast furnace slag (BFS), considering compressive strength, CO₂eq emissions, and production cost. A factorial experimental design was adopted with cement replacement by BFS (%CR) at 0%, 40%, and 80%, fines-to-aggregate ratio (%FA) at 18%, 20%, and 22%, and curing times of 7, 28, 56, and 91 days. Compressive strength was experimentally determined, while the environmental assessment was performed through a cradle-to-gate Life Cycle Assessment (LCA), using 1 m³ of concrete as the functional unit. Costs were estimated based on material consumption and local databases. The results showed that 40% BFS resulted in compressive strength values close to those of the reference mixtures at later ages, while 80% BFS reduced strength by approximately 28%. CO₂eq emissions decreased from 259 kg CO₂eq/m³ in C-18 to 90.3 kg CO₂eq/m³ in 80E-18. Cost reductions of approximately 14% and 29% were obtained for 40% and 80% BFS, respectively. Response surface methodology combined with desirability analysis indicated an estimated optimal cement replacement level of 58.94% by BFS and 18% FA, with global desirability of 79.09%.