Investigating the flexural strength characteristics of reinforced concrete beams utilising waste glass powder as a sustainable cement alternative

While concrete modified with waste glass powder (GP) displays promising mechanical and durability properties, data on the flexural strength characteristics of reinforced concrete sections under controlled laboratory conditions remains scarce. Existing studies frequently rely on smaller-scale specimens and shorter ageing tests (typically 28 days), often overlooking potential long-term effects and the unexplored impact of GP particle size. This study addresses this gap by investigating the flexural strength and behaviour of reinforced concrete beams incorporating GP as a partial cement substitute at 180 days. Fourteen beams (200 × 250 × 2000 mm) were tested, utilising two GP particle sizes (55 µm < GP-A < 135 µm and 55 µm > GP-B) at replacement levels ranging from 0 to 15% for two distinct cement contents. The investigation of flexural strength characteristics encompasses cracking behaviour, load-carrying capacities, deflections, stiffness, ductility, and the relationship between load and concrete compressive strain. Moreover, the validity of applying ACI318-19 code formulas for determining the flexural strength of traditional reinforced concrete to reinforced GP-modified concrete is explored. The test results revealed that the impact of GP particle size on the strength characteristics of beams was practically negligible, unlike the GP substitution level. In addition, with the exception of deflection ductility, the flexural strength characteristics of GP-containing beams were nearly identical to those of corresponding conventional concrete specimens. Incorporating GP into beams resulted in an overall increase in deflection ductility, implying that GP beams have a relatively high capacity to withstand large deflections before failing. The analytical results verified that the ACI318-19 code equations satisfactorily predicted the nominal flexural strength of GP-concrete sections. Overall, the findings highlight the long-term structural viability of GP-modified concrete, suggesting its potential application in reinforced concrete structures without compromising flexural strength.