Meso-fracture model of ultra-high-performance fiber-reinforced geopolymer concrete pertinent to aggregate gradation and fiber spacing

Ultra-high-performance fiber-reinforced geopolymer concrete (UHPFRGC) is an innovative building composite characterized by the dual attributes of ultra-high-performance concrete (UHPC) and geopolymer concrete. In this paper, a meso-fracture model pertinent to aggregate gradation and fiber spacing was proposed to analyze the fictitious crack development based on the boundary effect model (BEM). When the prefabricated crack tip was equivalent to rectangular stress distribution under peak load, the size-independent fracture parameters could satisfy the minimum accuracy requirements. Compared with size effect model (SEM), the fracture toughness (KIC) error of the UHPFRGC series calculated by the proposed meso-fracture model ranged from 3.37 % to 12.20 %. Moreover, a simplified method was developed to determine the sizeindependent fracture parameters precisely when the ratio of maximum and minimum equivalent crack growth length was approximate to 4 (ae,max: ae,min approximate to 4). Finally, the fracture failure curves were developed to predict the structural behavior, and minimum size satisfying the linear elastic fracture mechanics (LEFM) was given. This research work addresses the crucial technical issues of material parameter determination and structural behavior evaluation in the design and construction of UHPFRGC.