Sealing process induced by carbonation of localized cracks in cementitious materials

The healing of cracks plays an important role with regard to the air- and water-tightness of concrete structures and the durability of cement based materials in general. This paper aims at further characterization and better comprehension of the healing phenomenon induced by the precipitation of calcite in localized cracks. The experimental program consisted in generating a localized crack in a cement paste or concrete specimen and healing the crack created by percolation tests with carbonated water or gas (CO2-air mixture). For tests with liquid, results show that the healing process depends on physical parameters like crack width, pressure gradient and carbonate content in the percolating fluid. For tests with gas, the supply of the crack with Ca2+ ions to form calcite depends on the moisture transport mode on the crack edges, conditioned by the relative humidity of the percolating gas mixture. A simplified model of the leakage rate evolution is proposed. It provides indications concerning the effect of each test parameter on the healing process and allows the experimental results to be reproduced. Application of the model to other tests from the literature shows its limits and gives guidance for future investigations. (C) 2012 Elsevier Ltd. All rights reserved.