Test Method for Evaluating Healing Efficiency of Cracked Early-Age Concrete

Early-age concrete is susceptible to cracking due to volume change as cement hydrates. Cracks in concrete pose a durability and economic challenge with billions of dollars needed to repair or replace existing concrete infrastructure in Canada and the USA. Standard laboratory tests have been developed to evaluate concrete susceptibility to cracking at an early age such as ASTM C1581 – “Standard test method for determining age at cracking and induced tensile stress characteristics of mortar and concrete under restrained shrinkage”. Moreover, autogenous and autonomous self-healing processes are being studied to determine their pros and cons as repair methods for damaged concrete. Of interest is the use of capsules with healing agents, being polymeric or bacterium, in concrete being touted as an effective and least intrusive autonomous repair method for cracked concrete. This paper examines the viability of extending ASTM C1581 to test the effectiveness of adding capsules to heal cracks in young concrete. Analytical models were developed to simulate ASTM C1581 test results and to study the performance of capsules when encountering a crack in young concrete. This study examines the sensitivity of ASTM C1581 results to aging and mixture composition of concrete, and the capsule’s geometries and properties. The results reveal that the test is sensitive and viable. Adaptation of ASTM C1581 and C1585 is proposed to evaluate the performance of the self-healing system, specifically its efficiency.