Lignosulfonate-based superplasticizer derived from Borassus flabellifer L. biomass for enhanced concrete workability

A Lignin-derived bio-based admixture (LSBFB) was synthesized from Borassus flabellifer L. flower biomass through acid hydrolysis and chemical modification. The synthesized admixture exhibited a yield of 55.2 ± 4.8%, a homogeneous dark-brown appearance, a density of 1.15–1.25 g cm −3 , and a moisture content of 3–8%. It was characterized using FTIR, Raman, UV-Visible spectroscopy, DLS, and SEM. The admixture was incorporated into M30 grade concrete at different dosages to evaluate its fresh, mechanical, and durability properties. Among the investigated dosages, 1% admixture by mass of cement exhibited the best overall performance, increasing slump and 28-day compressive strength by 21.4% and 14.3%, respectively, with corresponding improvements in flexural and split tensile strengths. Initial and final setting times increased by 20% and 16.4%, respectively. Water absorption and RCPT charge decreased by 22.9% and 35.7%, respectively. Under sulfate exposure, the 1% LSBFB mixture exhibited a 50% reduction in mass loss and an increase in compressive strength retention from 86% to 90.9% compared with the control. SEM-EDS examination of hardened concrete further supported the observed modification of matrix morphology and elemental characteristics. These findings demonstrate the potential of Borassus flabellifer flower biomass as a renewable source of bio-based concrete admixture, contributing to agricultural waste valorization and sustainable construction.