Packing theory-based mixture design and performances evaluation of Ultra-high performance concrete

Abstract

Zirconium silica fume (ZrSF) is a type of silica-rich amorphous waste by-product obtained during the zirconium silicate electrofusion process. In this research, ZrSF is added to ultra-high performance concrete (UHPC) and an effective method for developing UHPC by incorporating ZrSF is addressed in this study. The main purpose of this study is to design UHPC based on the modified Andreasen and Andersen particle packing model. Meanwhile considering the effects of hydration reaction and the pozzolanic reaction of amorphous admixtures on the performance of UHPC, get the optimum mix proportion. The physical and chemical characteristics of the designed UHPC are evaluated, including the fresh and hardened state behavior. The workability, pore size distribution and compressive strengths of UHPC are tested and analyzed. The results show that the compressive strength of designed UHPC achieves 161 MPa with high flowability and lowest porosity. By calculating the content of calcium hydroxide in the sample, the reaction degree of different groups of pozzolans can be reflected. The pozzolanic reaction of ZrSF depletes portlandite and induces the formation of more C-S-H gels which further enhance the microstructure of UHPC matrix. On the other hand, UHPC matrix is significantly densified by the filling effect, because the voids present in the matrix can be filled with undissolved quartz particles.