Recycling of Eggshell Powder and Wheat Straw Ash as Cement Replacement Materials in Mortar

Cement is among the important contributors to carbon dioxide emissions in modern society. Researchers are studying solutions to reduce the cement content in concrete to minimize the negative impact on the environment. Among these solutions is replacing cement with other materials, such as waste, which also poses environmental damage and requires landfill areas for disposal. Among these wastes are eggshell powder ash (ESPA) and wheat straw ash (WSA), which were utilized as cement substitutes in green mortar production. Thirteen mixtures were cast, one as a reference without replacement and twelve others that included replacing ESPA and WSA (single and combined) with cement in 2%, 4%, 6%, and 8% proportions of cement's weight. The mechanical (compressive and flexural strength), microstructural (SEM), and thermogravimetric analysis (TG/DTA) properties of all mixtures were examined. The results showed a remarkable improvement in mechanical properties, and the best improvement was recorded for the (4%ESPA+4%WSA) mixture, which reached 73.3% in compressive strength and 56% in flexural strength, superior to the reference mixture. Furthermore, SEM analyses showed a dense and compact microstructure for the ESPA and WSA-based mortars. Therefore, the WSA and ESPA wastes can be recycled and utilized as a substitute for cement to produce an eco-friendly binder that significantly improves the microstructural and mechanical characteristics of mortar. In addition, combining the two materials also presents a viable option for creating a sustainable ternary blended binder (with cement) that boasts superior properties compared to using the WSA or ESPA individually

Effect of Clay Brick Waste Powder on the Fresh and Hardened Properties of Self-Compacting Concrete: State-of-the-Art and Life Cycle Assessment

Sustainability and reducing environmental damage caused by CO2 emissions have become issues of interest to researchers in the construction sector around the world. Reducing the cement content in concrete by partially substituting it with by-products or waste falls within this field as the cement industry is responsible for 7% of global CO2 emissions. On the other hand, self-compacting concrete (SCC) is one of the special types of concrete that contains a large amount of powder (most of which is cement) to ensure its flow under the influence of its weight without separating its components. Therefore, to produce eco-friendly SCC, many researchers have replaced part of the cement with clay brick waste powder (CBWP) since brick units are among the most widely used building materials after concrete. Accordingly, this study aims to review previous research that included using CBWP in SCC. The effect of these wastes on the fresh, mechanical, durability and microstructural properties of cement was reviewed. Additionally, a comparison between the environmental impacts of SCCs with different CBWP contents has been conducted using the life cycle assessment (LCA) approach. It was found that the highest value of CBWP that can be used without negatively affecting the different properties of concrete is 10% by weight of cement. Moreover, regarding environmental impact, using CBWP as a substitute for cement reduces environmental damage, and the lowest environmental impact that can be achieved per strength unit (MPa) is 37.5%