Evaluation of combined utilization of marble dust powder and fly ash on the properties and sustainability of high-strength concrete.

With the recent increase in demand for high-strength concrete, higher cement content is utilized, which has increased the need for cement. The cement industry is one of the most energy-consuming sectors globally, contributing to 10% of global carbon dioxide (CO2) gas emissions and global warming. Similarly, with rapid urbanization and industrialization, a vast number of by-products and waste materials are being generated in abundance, which causes environmental and health issues. Focusing on these two issues, this study aimed to develop an M50-grade eco-friendly high-strength concrete incorporating waste materials like marble dust powder (MDP) and fly ash (FA) as partial cement replacement. 2.5%, 5%, 7.5%, and 10% MDP and FA by weight of total binder was utilized combinedly, such that the 5%, 10%, 15%, and 20% cement content was replaced, respectively. The fresh state properties in terms of workability and hardened state properties in terms of compressive and flexural strengths were evaluated at 7, 14, 28, 56, and 90 days. Furthermore, to assess the environmental impact of MDP and FA, the embodied carbon and eco-strength efficiency were calculated. Based upon the results, it was observed that a combined 10% (5% MDP and 5% FA) achieved the highest strength; however, 15% (7.5% MDP and 7.5% FA) substitution could be optimal. Furthermore, the combined utilization of FA and MDP also enabled a reduction in the total embodied carbon. It decreased the cost of concrete, resulting in an eco-friendly, high-strength concrete.

Production of eco-friendly concrete incorporating rice husk ash and polypropylene fibres.

The use of supplementary cementitious materials (SCMs) has increased over the years due to the carbon footprint associated with the production of cement, which contributes to 10% of  the total global CO2 gas emissions. This causes an increase in global warming, and the exponential increase in demand for construction of concrete has caused depletion of natural resources. Furthermore, due to increased urbanisation, large quantities of agro-industrially processed waste materials are generated and dumped into landfills, causing significant land scarcity, environmental issues, and pollution. Therefore, it has become necessary to reduce the CO2 emissions by reducing our dependency on cement as a binder and developing eco-friendly concrete using alternative binders from agro-industrial waste materials. This study utilises Rice Husk Ash (RHA) as SCM and reinforcing with polypropylene (PP) fibres. The cement content is replaced with 5 to 20% RHA with an increment of 5% while reinforcing with PP fibres ranging from 0.20 to 0.30%. Based upon the results, it can be observed that concrete incorporating 15% RHA and reinforced with 0.25% PP fibres achieved better performance than the specimen with no SCM. However, a further increase in RHA content decreased concrete strength, which could not be recovered entirely with the reinforcement of PP fibres, though concrete with higher (20%) RHA reinforced with PP fibres could be used for non-structural and low-cost construction.