Development of high strength light weight concrete for RC beams by using optimum replacement level of pumice aggregate

In the present study, the main aim is to reduce the self-weight of the structure by developing High Strength Light Weight Concrete (HSLWC) for structural applications by identifying the optimum percentage replacement of pumice aggregate to Conventional Coarse Aggregate (CCA). In the present scenario, lightweight concrete has gained significant interest due to its potential for reducing structural dead load, enhancing seismic performance, and improving construction sustainability. The pumice aggregate is readily available but underutilized waste material from the textile industry, which remains largely unexplored in the context of high strength concrete. The density of pumice aggregate is <1000 kg/m3 having a very low density compared to CCA. The research gap lies in the lack of comprehensive studies that evaluate the structural performance of pumice as a partial replacement for CCA in high strength concrete, particularly used for structural components. The basic tests such as impact and crushing test were conducted on various percentages of replacement of pumice to CCA, which gives a clear idea of the replacement level suitable for structural concrete. The replacement level of pumice aggregate by 25% and 50% in volume to CCA shows the acceptable value, which is appropriate for structural concrete. The concrete mix was designed for the M-50 grade of concrete (i.e., the compressive strength of concrete is 50 N/mm2). The basic test on hardened concrete suggests that the 25% and 50% replacement of pumice to CCA by volume was ideal replacement to achieve the required strength. Totally six beams were cast; in this, two control beams were kept as the reference and the remaining four beams were bifurcated into two beams, each having 25% and 50% pumice replacement, respectively, to CCA. The beams were designed for tension failure as under reinforced sections in accordance with IS: 456-2000. The four point bending test was performed for all the beams. The research identified that 50% pumice replacement exhibited the most promising results, with a dry density of 1919 kg/m3, meeting the HSLWC criteria of a density <2000 kg/m3. Although there was a minor reduction in flexural strength with pumice replacement, the beams maintained their structural integrity and met serviceability criteria. These findings demonstrate that pumice can effectively reduce the weight of concrete structures while still providing adequate strength for practical use, especially in scenarios where reducing dead load is critical. This study contributes to the growing body of knowledge on sustainable construction materials and offers a viable solution for creating lightweight, high-strength concrete using pumice as an industrial waste product.