Flexural behaviour, cracking, and serviceability of sustainable RC beams with waste glass fine aggregate and pond ash

This study investigates the flexural behaviour of steel-reinforced concrete beams incorporating waste glass fine aggregate (GFA) and unprocessed waste coal ash, known as pond ash (PA), as sustainable alternatives to conventional materials. Driven by environmental concerns over natural sand extraction and the diminishing availability of fly ash for alkali-silica reaction mitigation, the research explores the combined use of GFA and PA to produce sustainable concrete. Concrete tests, including compressive strength, splitting tensile strength, and flexural strength, were conducted to evaluate the mechanical performance. A series of RC beams were cast with varying replacement levels of conventional fine aggregates by GFA (0 %, 20 %, and 40 %) and with ordinary Portland cement (OPC) partially replaced by 20 % of PA. The beams were tested under three-point bending at 28 days and six months, with digital image correlation employed to capture crack propagation and deformation characteristics. The performance of beams was evaluated regarding crack initiation and propagation, crack width evolution, failure mode, load-deflection response, yield and ultimate loads, stiffness, ductility, and energy absorption capacity. The results showed that while GFA increased cracking at 28 days, it reduced crack widths at six months. The addition of PA significantly decreased crack widths at both ages, enhancing serviceability. Yield and ultimate loads remained within ±10 % of the control for all mixes, indicating minimal structural compromise. These results demonstrate that waste glass and unprocessed pond ash can be successfully used in RC beams without sacrificing flexural performance, offering a practical path toward more sustainable structural concrete. • Waste glass and pond ash as sustainable alternatives to conventional materials. • Flexural test on RC beams containing glass and pond ash at 28 days and 6 months. • Utilisation of digital image correlation to investigate the crack behaviour. • Waste glass increases cracking while the inclusion of pond ash reduces it. • Both glass and pond ash have no significant impact on yield and ultimate failure.