Predictive modeling for mechanical characteristics of ultra high-performance concrete blended with eggshell powder and nano silica utilizing traditional technique and machine learning algorithm

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The construction industry currently utilizes nanomaterials to improve the mechanical performance of ultra-high-performance concrete (UHPC). Eggshell powder has recently gained popularity in the fields of construction and building materials owing to its local availability and better cementitious properties. In addition, the use of advanced mix design techniques has recently become popular for saving experimental cost and time. This study aims to assess the effects of new composite material using eggshell powder pre-mixed with nano-silica as a partial substitute for cement in the production of UHPC and develop models using Response Surface Methodology (RSM) and Artificial Neural Networks (ANN). Eggshell powder was substituted at different ratios, such as 2.5, 5, 7.5, 10, and 12.5 %, in plain UHPC for reference. Additionally, a new composite of eggshell powder premixed with nano silica in UHPC was developed for comparison. Mechanical properties such as compressive strength, splitting, and flexural strength were investigated in addition to sorptivity and microstructure analysis using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Furthermore, the developed (ANN + RSM) models showed a high level of accuracy with the actual results and showed that these models can be employed to determine the mechanical characteristics of UHPC incorporating eggshell powder. The R2 value, experimentally predicted variation, and error analysis showed that the ANN model was more accurate than the RSM model. The experimental results showed that the optimum results were obtained with better mechanical performance and a densely packed microstructure for a 10 % replacement ratio when the eggshell powder was pre-mixed with nano-silica. According to this study, ES and ES-PNS as partial cement replacements in UHPC reduce CO2 emissions and material costs. ES and ES-PNS in ultra-high-performance concrete production have environmental and economic benefits.