Experimental and RSM-based optimization of sustainable concrete properties using glass powder and rubber fine aggregates as partial replacements

Abstract

To promote sustainability in concrete production, this study investigates the combined use of glass powder (GP) and rubber fine aggregates (RF) as partial replacements for cement and natural fine aggregates (NF), respectively. The study aligns with several Sustainable Development Goals (SDGs). Ten mixtures were developed using Central Composite Design (CCD) within the Response Surface Methodology (RSM) framework, with GP and RF replacement levels ranging from 0 % to 35 %. Replacing cement with 15 % GP improved compressive strength, tensile strength, and stiffness due to pozzolanic reactivity and packing effects, while higher levels (25–35 %) reduced performance because of increased water demand and dilution. RF replacement up to 15 % maintained workability and strength; beyond this, mechanical properties declined due to RF’s low specific gravity (1.06 g/cm3), weak bonding, and higher porosity. The optimal mix, GP15RF15, achieved a slump of 92 mm, 28-day compressive strength of 40.1 MPa, tensile strength of 5.3 MPa, and modulus of elasticity of 25,914.5 MPa, comparable to the control mix. Correlation analysis showed strong positive relationships among compressive strength, tensile strength, and stiffness (r ≥ 0.99), while RF content had strong negative correlations (r = −0.75 to −0.77). Optimization using the desirability function yielded a score of 1.000, with prediction errors below 1.35 %. The results confirm the viability of GP–RF concrete as a durable and eco-efficient alternative for non-prestressed structural components and general infrastructure.