Mechanical and Volumetric Changes of Sustainable Lightweight Fibrous Concrete with Fine Recycled Aggregate and Silica Fume

Abstract

This study presents an experimental program aimed at producing durable and sustainable lightweight concrete using lightweight expanded clay aggregate (LECA) as coarse aggregate, With the completely replacement of fine aggregate with recycled concrete aggregate. To enhance the quality of the cementitious matrix and its long-term behavior, 15% silica fume and 1% steel fiber were incorporated into the mixtures. Five mixtures were prepared with a water to cement ratio of 0.4: NFA-based mix and four modified mixes with the addition of silica fume, steel fibers or a combination of both. Mechanical properties and durability were evaluated through several tests including compression strength, tensile strength, dry density, water absorption, dry shrinkage and wet expansion which were evaluated at two curing ages of 28 and 90 days. The findings indicate that the use of RFA as a full replacement for NFA led to a noticeable reduction (about 15%) in strength at 28 days. The use of steel fibers improved the splitting tensile strength by up to 20% compared to the control mixture. The combined effect of blending SL and MSF demonstrated a substantial enhancement in the mechanical performance. The compressive and tensile strengths increased by approximately 13% and 33%, respectively, at 90 days. Using silica fume together with steel fiber effectively reduced the elevated water absorption typically observed in mixture containing RFA. In addition, the blend showed reduced volumetric change, with reductions of 26% in shrinkage and 41% in expansion. The results showed the effectiveness of the use of pozzolan materials and fibers in the development of SLWC using recycled aggregates while improving durability and strength.