Comprehensive study on the mechanical property and fracture behavior of ultra-high strength concrete

Abstract

In order to figure out the relationship between mechanical property and fracture behavior of UHSC and investigate its influencing factors, a series of UHSC with different mix proportion have been prepared. The mechanical properties (including compressive strength, flexural strength, and splitting tensile strength) were tested on a hydraulic servo universal testing machine. Three-point bend loading method was used to measure the fracture parameters (including fracture toughness and characteristic length) and a crack was prefabricated in the sample. The results show that the strength of UHSC decreases with w/b ratio and the maximum compressive strength and flexural strength can reach 132 MPa and 21.5 MPa, respectively. UHSC displays significant brittle fracture behavior and its brittleness increases with strength. The main reason is that the micro-defects of UHSC are reduced and the homogeneity of the whole cement matrix is enhanced, thus the crack initiation strength is improved but crack resistance ability is impaired. High temperature curing increases the strength as well as brittleness of UHSC. Adding fly ash will improve its characteristic length but reduce the facture toughness. Our work may provide guidance for reducing the brittleness of ultra-high strength concrete.