Durable concrete structures with cracks which heal themselves

Abstract

Concrete is one of the most widely used construction materials due to its excellent mechanical properties and relatively low cost. However, concrete is prone to crack formation. These cracks do not impair the structural integrity, but they endanger the durability of the structure as aggressive liquids and gasses may enter via these cracks and cause degradation. Therefore, crack repair is needed but these repair works increase the cost of concrete structures by 50% as they are labour intensive and because the structure becomes in discuse during repair. Accordingly, in this research it was investigated whether cementitious materials can be modified so that cracks heal themselves. Therefore, healing agents were encapsulated by brittle capsules and embedded inside the cementitious matrix in the zones where cracks were expected. When the matrix starts cracking, the capsules break and release their content, leading to crack repair. Water absorption measurements were performed to evaluate the healing efficiency. The amount of absobed water was determined by gravimetrical measurements and visualized by X-ray radiography. When samples with untreated cracks were placed with their cracked surface in a water reservoir, it was noticed from the radiographs that water penetrated very fast into the cracks. For samples with self-healing properties no water entered into the cracks. Moreover, even in the zone alongside the crack no water entry was noticed. Therefore, it can be concluded that self-healing of concrete cracks can be used to prevent the ingress of liquids and to prevent subsequent damage to the matrix.