Comprehensive Performance Evaluation of C Class Fly Ash Stability and Activity Index Based on Projection Pursuit Regression

To better evaluate the comprehensive performance of Class C fly ash (FA) in terms of soundness and mechanical strength for engineering applications, this study analyzes the effects of CaO and free-CaO (f-CaO) on the strength activity index and soundness of FA. A prediction model for FA strength and soundness is established based on the projection pursuit regression (PPR) method. Through simulation calculations, contour maps of comprehensive performance are drawn, transforming the multi-objective performance optimization problem into single-objective optimization problems of mechanical strength and soundness. The model directly determines the strength activity and soundness of fly ash under different CaO and f-CaO contents. The results indicate that when the f-CaO content does not exceed 4.82%, increasing the CaO content can both ensure the soundness of FA and improve its strength activity index. This study provides guidance for the application of Class C FA in concrete engineering.