Experimental and analytical study of ultra-high-performance fiber-reinforced concrete modified with egg shell powder and nano-silica

Presently, the rate for the development of ultra-high-performance concrete (UHPC) is increasing due to the requirement of long-span bridges, challenging architectural plans, and high-rise buildings. UHPC is still weak in tension and consumes a lot of cement, making it non-eco-friendly. This research is aimed at modifying the cement's matrix by incorporating two sustainable solid waste mineral admixtures, eggshell powder (ESP) and nano-silica (NS), to enhance the bonding between fibers and the binder's matrix and improve the strength characteristics of ultra-high-performance fiber-reinforced concrete (UHPFRC). The improving impacts of the ESP and NS on the double-hooked end (DHE) steel fibers were studied and analyzed by evaluating various strength parameters, i.e., compressive, splitting tensile and flexural strength and the load-deflection performance. To characterize the durability properties of UHPFRC, chloride ion coefficient, ultra-sonic pulse velocity (UPV), and water absorption tests were also carried out. Optimization of added materials was also done using a statistical tool called a design of experiments. Multi variable statistical analysis was performed using response surface methodology (RSM) and analysis of variance (ANOVA). Both the experimental and statistical test outcomes depicted that introducing 5% ESP and 5% NS significantly improved the effectiveness of DHE steel fibers when the concrete was subjected to splitting tensile and flexural strength. UHPFRC with the 5% ESP and NS depicted 81% and 94% higher flexural strength than the reference mixture. While UHPFRC had almost 35 times higher flexural toughness than its counterparts. The inclusion of 5% and 10% eggshell powder depicted a favorable impact on the resistance of UHPFRC against the infiltration of water and chloride ions. The test outcomes of the present research confirmed the suitability and effectiveness of using ESP and NS as a partial substitute for OPC and significantly improved the engineering properties of UHPFRC, which was verified by the analytical results.& COPY; 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).