Self healing capability of concrete containing crystalline admixtures in different exposure conditions

Self-healing materials have the capability of recovering their performance after damage has occurred. In this work, the self-healing effect of a crystalline admixture for concrete is analysed in different environmental exposures. In order to compare healing capacity of the admixture compared with autogenous healing of concrete, two types of concrete were studied: a control concrete (CC) and a mix containing the crystalline admixture (CAC), with a dosage of 4% by the weight of cement. Four exposure conditions were studied: water immersion, water contact with a water layer of two centimetres, humidity chamber and laboratory conditions. Self-sealing/healing was studied by analysing the permeability of the cracked specimens and by observing with a microscope the closing of the crack. As from the obtained results CAC showed better healing behaviour than CC; the healing rates of CC had higher dispersion than those of CAC, which achieved more stable behaviour for all the different exposures and was anyway able to provide some not negligible healing capacity also in open air conditions. Differences between the exposures with direct contact with water were also noticed, indicating the importance of water for the reaction to take place.