Synergistic Effects of GGBS Cement Replacement and Crumb Rubber Aggregate on the Fresh, Mechanical, and Durability Performance of Structural Concrete

https://doi.org/10.46610/JoCCS.2025.v010i03.001

Abstract

This study investigates the influence of ground Granulated Blast Furnace Slag (GGBS) as a cement replacement (0–60% by mass of binder) and crumb rubber (CR) as a partial natural fine-aggregate replacement (0–20% by volume) on the fresh properties, mechanical performance, durability, and microstructure of structural concrete targeting 30 MPa characteristic compressive strength at 28 days (M30). A 4×5 full-factorial experimental matrix (GGBS: 0, 20, 40, 60%; CR: 0, 5, 10, 15, 20%) was designed at a constant water-to-binder ratio (w/b = 0.40) with a high-range water reducer to achieve comparable workability. Tests included slump, density, air content, and compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, ultrasonic pulse velocity (UPV), water absorption, sorptivity, bulk electrical resistivity, and rapid chloride permeability (RCPT). Selected mixes underwent sulphate exposure and microstructural characterization (SEM/EDS, and XRD). Results (to be populated with measured values) are expected to show that (i) GGBS enhances late-age strength and improves transport properties; (ii) crumb rubber reduces density and static modulus while improving impact resistance and freeze-thaw resilience; and (iii) optimal performance occurs at 40% GGBS with 5–10% CR, yielding acceptable strength and significantly improved durability. Statistical analysis (ANOVA, response surfaces) quantifies main and interaction effects. Sustainability assessment indicates embodied-CO₂ reduction proportional to GGBS content and diversion of tire waste through CR utilization.