High-Strength Lightweight Silica Fume Concrete with Fine Recycled Aggregate and Steel Fiber

Abstract

Sustainable lightweight concrete presents a promising solution for reducing environmental pollution caused by construction and demolition waste. This study focuses on developing high-strength lightweight concrete (HSLWC) using lightweight expanded clay aggregate (LECA) as coarse aggregate and fully replacing natural fine aggregate (NFA) with recycled fine aggregate (RFA). To enhance performance of the produced mixes, 15% silica fume and varying contents of micro steel fibers (0.5% and 1%) were incorporated. Seven concrete mixtures were prepared with a low water to cement (w/c) ratio of 0.25 and tested at 28 days to evaluate slump flow, compressive strength, splitting tensile strength, density, and water absorption. The results revealed that using 100% RFA reduced compressive strength from 54.5 MPa to 45.7 MPa and splitting tensile strength from 4.67 MPa to 4.03 MPa. However, the inclusion of 1% steel fibers compensated for this reduction, raising compressive strength to 55.1 MPa and splitting tensile strength to 5.89 MPa. Further enhancement was observed when silica fume was combined with steel fibers, resulting in a maximum compressive strength of 58.1 MPa and a splitting tensile strength of 6.11 MPa. These values exceeded those of the reference mix made with NFA. The combined use of silica fume and steel fibers led to the most effective improvement, producing sustainable HSLWC with superior mechanical performance, reduced water absorption, acceptable workability, and structural lightweight density