Development of fiber-reinforced lightweight concrete incorporating novel popcorn coarse aggregate

Abstract

This study explores the potential of popcorn coarse aggregate (PCA), a byproduct of recycled polyester fiber manufacturing, as a lightweight and sustainable replacement for natural coarse aggregate (NCA) in concrete. Thirteen concrete mixtures were prepared in two phases. The first phase involved replacing NCA with PCA at 0%, 25%, 50%, 75%, and 100% by volume. In the second phase, the optimal PCA75 mixture was further enhanced using polypropylene fibers (PPF) and glass fibers (GF) at volumetric dosages of 0.25%, 0.50%, 0.75%, and 1.0%. Evaluated properties included slump, unit weight, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, water penetration, and microstructural features. Results showed that replacing NCA with PCA significantly reduced concrete density from 2390 kg/m3 in the PCA0 mix to 1875 kg/m3 in PCA75 and 1735 kg/m3 in PCA100. All mixes met the lightweight concrete classification criteria. However, compressive strength declined with increasing PCA content, dropping from 38.8 MPa in PCA0 to 30.5 MPa in PCA75 and 26.0 MPa in PCA100. Strong negative and positive correlations were observed between compressive strength and PCA (r = − 0.916) and NCA (r = + 0.925), respectively. Among the fiber-reinforced mixes, the incorporation of 0.25% GF was identified as the optimal dosage, improving compressive strength by 3.3%, splitting tensile strength by 18.7%, and flexural strength by 14.6%. Correlation analysis identified PCA and NCA as the most influential parameters, with correlation coefficients above 0.82, while PPF and GF showed moderate positive effects with r values of 0.473 and 0.332, respectively. SEM analysis revealed improved matrix densification with GF and increased porosity in high-PCA mixes.