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.

Experimental study on fresh, mechanical properties and embodied carbon of concrete blended with sugarcane bagasse ash, metakaolin, and millet husk ash as ternary cementitious material.

In recent years, the research direction is shifted toward introducing new supplementary cementitious materials (SCM) in lieu of in place of Portland cement (PC) in concrete as its production emits a lot of toxic gases in the atmosphere which causes environmental pollution and greenhouse gases. SCM such as sugarcane bagasse ash (SCBA), metakaolin (MK), and millet husk ash (MHA) are available in abundant quantities and considered as waste products. The primary aim of this experimental study is to investigate the effect of SCBA, MK, and MHA on the fresh and mechanical properties of concrete mixed which contributes to sustainable development. A total of 228 concrete specimens were prepared with targeted strength of 25MPa at 0.52 water-cement ratio and cured at 28 days. It is found that the compressive strength and split tensile strength were enhanced by 17% and 14.28%, respectively, at SCBA4MK4MHA4 (88% PC, 4% SCBA, 4% MK, and 4% MHA) as ternary cementitious material (TCM) in concrete after 28 days. Moreover, the permeability and density of concrete are found to be reduced when SCBA, MK, and MHA are used separately and combined as TCM increases in concrete at 28 days, respectively. The results showed that the workability of the fresh concrete was decreased with the increase of the percentage of SCBA, MK, and MHA separately and together as TCM in concrete.

Effect of local metakaolin developed from natural material soorh and coal bottom ash on fresh, hardened properties and embodied carbon of self-compacting concrete.

The carbon dioxide emissions from Portland cement production have increased significantly, and Portland cement is the main binder used in self-compacting concrete, so there is an urgent need to find environmentally friendly materials as alternative resources. In most developing countries, the availability of huge amounts of agricultural waste has paved the way for studying how these materials can be processed into self-compacting concrete as binders and aggregate compositions. Therefore, this experimental program was carried out to study the properties of self-compacting concrete (SCC) made with local metakaolin and coal bottom ash separately and combined. Total 25 mixes were prepared with four mixes as 5, 10, 15, and 20% replacement of cement with metakaolin; four mixes as 10, 20, 30, and 40% of coal bottom ash as partial replacement of fine aggregates separately; and 16 mixes prepared combined with metakaolin and coal bottom ash. The fresh properties were explored by slump flow, T50 flow, V-funnel, L-box, and J-ring sieve segregation test. Moreover, the hardened properties of concrete were performed for compressive, splitting tensile and flexural strength and permeability of SCC mixtures. Fresh concrete test results show that even if no viscosity modifier is required, satisfactory fresh concrete properties of SCC can be obtained by replacing the fine aggregate with coal bottom ash content. At 15% replacement of cement with local metakaolin is optimum and gave better results as compared to control SCC. At 30% replacement of fine aggregate is optimum and gave better results as compared to control SCC. In the combined mix, 10% replacement of cement with metakaolin combined with 30% replacement of fine aggregate with coal bottom ash is optimum and gave better results as compared to control SCC.