Multi-Objective Optimization of GGBS Blended Pervious Concrete: Coupling Mechanical Strength, Permeability, and Water Purification via Microstructure Control

Abstract

This study extends the design space of pervious concrete with respect to strength, drainage, and water purification using a multi-objective optimization approach. GGBS was used as a partial cement replacement (15–45%) across four no-fines coarse-aggregate gradations and assessed for compressive strength (accelerated, 7-day, and 28-day), constant and falling head permeability, and water filtration. The optimal formulation - a 60:40 blend by mass of the 16–10 mm and 10–4.75 mm coarse-aggregate fractions, with 30% GGBS - develops a compressive strength of 11.78 MPa at 7 days rising to 18.83 MPa at 28 days, together with a measured permeability coefficient of 2.0 mm/s and removals of 23.8% of dissolved solids and 10.2% of suspended solids. Microstructural images from SEM and porosity specifications indicate that slag modification densifies the interfacial transition zone without impeding drainage. Structure–property relationships align with previous studies indicating the presence of a design space with an optimal strength target for multifunctional properties. This evidence demonstrates that microstructural optimization via slag enables simultaneous structural and environmental performance, thereby promoting the use of pervious concrete in urban infrastructures.