The selection of an appropriate concrete mixture for casting a pile cap in hot weather using 3D finite element model

Abstract

In this study, the finite element model (FEM) was developed to select an appropriate concrete mixture for a large heavily reinforced bridge pile cap located in Qassim region of Saudi Arabia. The pile cap with dimensions of 9 m x 9 m in plan and 1.8 m in depth was exposed to hot weather conditions in summer season. The heat of hydration in mass concrete results in high temperature gradients across the depth of the concrete creating excessive thermal stresses resulting in micro-cracking at the surface. The concrete mixtures with 30% date kernels ash, 30% fly ash, 30% natural pozzolan, 30% limestone powder, 30% ground granulated slag and 60% ground granulated slag were investigated. The experimental investigations were conducted on the concrete mixtures to determine the mechanical properties, such as tensile and compressive strength, thermal properties, such as thermal conductivity, specific heat, and thermal resistivity, and heat of hydration. The chemical compositions of ordinary Portland cement, date kernels ash, fly ash, natural pozzolan, limestone powder and ground granulated slag were analyzed using wavelength dispersive X-ray fluorescence (WDXRF). Based on the experimental and finite element model results, the concrete mixtures with 30% fly ash (FA), 30% ground granulated blast furnace slag (GGBFS), and 60% GGBFS were found to be less prone to cracking. Notably, the mixture with 60% GGBFS demonstrated the lowest likelihood of cracking, leading to its selection for casting the pile cap.