Estimation of critical free expansions related to surface cracking in ASR-affected concretes

This paper proposes a simple procedure to determine the critical free expansion for macro-surface cracking in ASR-affected model concrete cylinders. It is assumed that the non-reactive near-surface concrete regions act as restraint against uniform expansion of the inner core due to ASR. The critical free expansion is calculated assuming that a longitudinal crack forms when the maximum circumferential tensile stress in the concrete cylinder reaches the tensile strength of the material. The expansive pressure that causes the tensile stress depends on degree of restraint, as determined from measured expansive pressures and free expansions. The calculated critical free expansions for concretes with various strengths at various depths of the non-reactive concrete cylinders can be used to qualitatively interpret the significance of suppression of ASR macro-cracking by drying and relatively lower probability of surface cracking in structures in indoor rather than outdoor environments. It appears the proposed procedure can be used for estimating critical free expansions independently of temperature.