Mohamad Ali-Ahmad

This study investigates the effect of mass-based replacement of natural coarse aggregate with electric arc furnace (EAF) slag on the performance of ordinary Portland cement (OPC) concrete. Replacement levels of 0%, 30%, 50%, and 100% were examined, with particular attention to the volumetric changes induced by the higher density of EAF slag, which leads to an increase in paste volume. Fresh, mechanical, durability-related, and microstructural properties were evaluated. Results show a continuous reduction in workability with increasing slag content, despite the increase in paste volume, indicating the dominant influence of aggregate morphology on rheological behavior. Mechanical performance exhibited a non-linear response. Within the tested series, the 50% replacement mixture showed the highest mean compressive and splitting tensile strengths; however, the compressive strength difference relative to the control mixture remained small and within typical experimental scatter. In contrast, water absorption decreased progressively, reflecting improved matrix densification. However, this densification did not translate into enhanced mechanical performance, highlighting a decoupling between durability-related indicators and strength. A screening-level CO₂ assessment further showed that reductions in aggregate-related emissions were offset by increased cement content associated with mass-based replacement. The results emphasize the importance of considering volumetric effects when interpreting the behavior and sustainability of slag-based concrete. Note: all strength comparisons are based on mean values from three-specimen sets without formal statistical testing and should be regarded as exploratory observations.

Background: Cement production is a significant source of global CO ₂ emissions, driving the need for sustainable alternatives in construction. Ground granulated blast-furnace slag (GGBS) has emerged as a promising supplementary cementitious material; however, its performance across wide replacement ranges and its combined environmental and economic implications remain insufficiently characterised, particularly in hot and arid climatic contexts such as the Gulf region. Methods: Nine mortar mixes incorporating GGBS as a partial replacement for ordinary Portland cement (OPC) were prepared at replacement levels ranging from 5% to 100%. Compressive and flexural strength were assessed at 7, 14, and 28 days of curing. Life cycle assessment (LCA) and life cycle cost (LCC) analyses were conducted to evaluate the environmental and economic performance of each mix over its service life. Results: Replacement levels between 20% and 30% yielded optimal compressive strength, surpassing the OPC control at 28 days. Higher replacement levels enhanced flexural strength, though the highest recorded values require further validation. LCA results confirmed a progressive reduction in CO ₂ emissions with increasing GGBS content, while LCC analysis demonstrated improved cost efficiency relative to the OPC reference. Discussion: A 30% GGBS replacement level is identified as the optimal balance between mechanical performance, environmental benefit, and economic efficiency. These findings support the adoption of GGBS-blended mortars as viable, sustainable alternatives to conventional OPC-based construction materials in the Gulf region and comparable climatic environments.

1. The shift to low-carbon construction materials has increased global interest in blended cements that use industrial by-products like ground granulated blast furnace slag (BFS). Reducing the clin...