Real-time detection and analysis of damage in high-performance concrete under cyclic bending.

In order to quantitatively evaluate the damage level in high-performance concrete (HPC) with pozzolanic minerals under constant amplitude cyclic loads, three methods for real-time damage detection are employed in the present work, i.e., dynamic modulus instrument, realtime strain collector, and digital speckle correlative method (DSCM). Six mechanical parameters at different numbers of loading cycles are real-time captured by these three methods. For a maximum applied fatigue stress equal to 70% of the static flexural strength, a cohesive crack is detected on the specimen surface by the DSCM system from 10% of concrete fatigue life. The nucleation and propagation of the cohesive crack is reflected by the change of the strain concentration zone in 2-dimensional strain fields. The experimental results show that the admixtures of Class F Fly Ash (FA) and S95 Ground Granulated Blast-furnace Slag (GGBS) in high proportions increase the strain and cohesivecrack opening displacement as well as remarkably improve the fatigue performance of HPC.