Influence of coarse aggregate size on deterioration of concrete affected by alkali-aggregate reaction

•Aggregate size significantly affects expansion and crack in AAR-affected concrete.•Splitting tensile strength linear decreases with AAR expansion.•Greater aggregates lead to a greater reduction in strength of AAR-affected concrete.•Damage index using microcracks at an early stage of AAR underestimates deterioration. The alkali-aggregate reaction (AAR) is one of the main factors to reduce the durability of concrete structures. Dam concrete contains very large aggregates, and the influence of coarse aggregate size on AAR-induced deterioration requires a deep understanding. In this paper, a mesoscale particle model of concrete was presented to simulate the AAR process and mechanical testing of AAR-affected concrete. Four types of concrete with different sizes of coarse aggregates were considered. The experimental AAR expansion of dam concrete containing aggregates up to 150 mm was used to validate the mesoscale model. The numerical simulation results show that the coarse aggregate size significantly affects the AAR expansion and the degradation of mechanical properties. Dam concrete with 150 mm aggregates exhibits smaller expansion but earlier cracks than general concrete with small coarse aggregates. The mechanical properties in terms of elastic modulus, compressive strength and splitting tensile strength are reduced more in concrete with larger aggregates at the same AAR expansion. These phenomena illustrate that it is not appropriate to assess the AAR-induced deterioration of the mechanical properties of dam concrete using an index based on concrete with 5 ∼ 20 mm aggregates.