Fracture Behavior of Cement-Based Materials

Abstract

The characterization of fracture behavior is a continuing challenge to the cement and concrete community. The performance of a material can be evaluated by its stress-strain response. For an ideally brittle material, elastic response is terminated when stress suddenly drops to zero, as shown in Figure 1a. However, cement-based materials are considered quasi-brittle because they respond nonlinearly prior to peak stress, and their stress gradually decreases after reaching a peak, as indicated in Figure 1b.To make cement-based materials stronger and tougher, one needs to understand the fracture mechanisms associated with nonlinear stress-strain behavior and to characterize material fracture properties based on these fracture mechanisms. Three novel techniques are being used at the Center for Advanced Cement-Based Materials (ACBM) to detect the quasi-brittle nature of cement-based materials. These three techniques are laser holographic interferometry, acoustic emission, and microscopic surface analysis. This article summarizes both the fracture mechanisms in cement-based materials and the application of the three techniques to characterize and measure fracture properties.