Crack Self-healing Behavior of Cementitious Composites Incorporating Various Mineral Admixtures

Tae-Ho Ahn and Toshiharu Kishi Journal of Advanced Concrete Technology, 8(2) 171-186, 2010 This study aims to develop and apply self-healing concrete as a new method for crack control and enhanced service life in concrete structure. This concept is one of the maintenance-free methods which, apart from saving direct costs for maintenance and repair, reduces the indirect costs - a saving generally welcomed by contractors. In this research, the self-healing phenomenon of autogenous healing concrete using geo-materials for practical industrial application was investigated. Moreover, a self-healing concrete was fabricated by ready-mixed car in a ready-mixed concrete factory, then used for the construction of artificial water-retaining structures and actual tunnel structures. The results show that the crack of concrete was significantly self-healed up to 28 days re-curing. Crack-width of 0.15mm was self-healed after re-curing for 3 days and the crack width decreased from 0.22 mm to 0.16 mm after re-curing for 7 days. Furthermore, it was almost completely self-healed at 33 days. It was founded that this phenomenon occurred mainly due to the swelling effect, expansion effect and re-crystallization. From these results, it is considered that the utilization of appropriate dosages of geo-materials has a high potential for one of new repairing methods of cracked concrete under the water leakage of underground civil infrastructure such as tunnels.

There are many approaches to achieve self-healing properties for concrete, however, very few of them are both technically and economically practical at the same time. This paper demonstrated a system of self-healing which is both technically and economically reasonable at present by introducing a system of mineral admixture using expansive agent as the basic material. The improvement for the effectiveness of the system was made by adding some minerals. Some achievements of this paper are the success of to solve 2 main problems for this sort of mineral-type crack healing agent which are to make the crack filling products fill the cracks at early age (within 3 days) and stable in longterm. (Prof. Somnuk Tangtermsirikul, Tammasat University)