Effect of silica fumes on fluidity of UHPC: Experiments, influence mechanism and evaluation methods

摘要

Silica fumes are adopted to densify the microstructure in UHPC, which has an obvious effect on fluidity of UHPC. It is still unclear to explain the influence mechanism of silica fume with different material properties on fluidity of UHPC systematically. In this paper, based on analytic hierarchy process (AMP), a new evaluation method of fluidity for UHPC is proposed through analyzing materials properties of silica fumes. In order to obtain the judgment matrixes of criteria in the evaluation method, five types of silica fumes are selected as mineral admixtures to measure fluidity of UHPC. Compressive packing model (CPM) is adopted to calculate the real packing density of silica fume-cement system. Moreover, influence mechanism and effect factors of silica fumes on fluidity of UHPC are explored. The results indicate that low void ratio, high packing density, wide particle size span and low carbon content can increase the fluidity of UHPC through enhancing "ball effect" and "plasticizing effect". Finally, the judgment matrixes of criteria in the evaluation method are developed by quantifying the effect factors, and evaluation methods can be adopted to evaluate the fluidity of UHPC with various silica fumes accurately. (C) 2019 Elsevier Ltd. All rights reserved.