Expansive cracking and compressive failure simulations of ASR and DEF damaged concrete using a mesoscale discrete model

Internal stresses induced by the alkali silica reaction (ASR) and delayed ettringite formation (DEF) can cause cracking and degrade the mechanical properties of concrete, but the relationship between these phenomena remains unclear. In this study, crack patterns and the loss of compressive strength and elastic modulus of concrete after ASR and DEF expansion are simulated at the mesoscale using a three-dimensional Rigid Body Spring Model (3D RBSM). Concrete expansions induced by ASR and DEF are introduced in the model by applying initial strain on the springs of interfacial transition zone (ITZ) and mortar elements as damage history respectively. After verifying the model with single aggregate, further analysis of differences in concrete cracking due to ASR and DEF damage is carried out. The effect of the percentage of reactive aggregate is studied in the cases of ASR damage, while different intensified expansion areas are considered in the case of DEF. The simulated losses of mechanical properties of the concrete are compared with the experimental results and good agreement is obtained. It is found that the loss of mechanical properties is dominated by internal cracks rather than the surface crack pattern. Compressive strength is highly dependent on the development of large cracks while elastic modulus is closely related to the total number of cracked faces. More importantly, regardless of the intensified expansion area, the mechanical properties are consistent with expansive cracking damage.