Damage source and its evolution of ultra-high performance concrete monitoring by digital image correlation and acoustic emission technologies

Abstract

Ultra-high performance concrete (UHPC) is a kind of fiber-reinforced cement-based materials with outstanding mechanical properties and much enhanced toughness. In this paper, digital image correlation (DIC) and acoustic emission (AE) techniques are used to study the damage mode of UHPC during loading process. The results demonstrate that the combination of DIC and AE can identify the internal damage sources and also detect the surface cracks in UHPC. With the addition of steel fibers, the strain of cracking point of UHPC exposed to steam curing is 1.61 times greater than that exposed to standard curing. Furthermore, the b-value analysis provides the critical value for UHPC damage, and the reference values for the warning threshold and warning time are proposed. Using RA-AF correlation analysis, UHPC displays a mixed damage with tensile damage predominating. By analyzing the intensity of the AE signal, the safety of UHPC (20% silica fume and 1% steel fibers) exposed to steam curing is 17 times higher than ordinary reinforced concrete beams. Moreover, the damage mode of UHPC is multi-point damage, which significantly increases the ultimate bending load and bending toughness of the UHPC, and improves bending resistance.