Exploration Of The Self-Healing Methods For Repairing Cracks Of Cement-Based Materials

Concrete plays an irreplaceable role in the country's infrastructure construction due to its convenient availability, low price and good compressive strength etc. However, because of concrete's low tensile strength, cracking can not be avoided in the practical application of concrete structure. The negative influence produced by concrete cracking includes the deterioration of both the mechanical properties and the ability to resist outside ions'infiltration. Generally speaking, the common repairing technologies of cracking are adopted after the appearance of concrete cracking, which are often resource-consuming and can sometimes cause irreparable loss before the concrete cracking is detected. So a smart cracking repairing technology is urgently needed, which means that the concrete can take actions to repair its own cracking without the involvement of human beings.Based on the development of self-repairing technology of concrete cracking all over the world, the use of adhesive to fill concrete cracking and then repair it after curing is adopted in this paper. In order to validate the effectiveness of this method, the compressive strength test of concrete cubes with repairing capsules added as function components, the three-point bending test of self-repairing concrete beams loaded with hydraulic jack and the three-point bending test of self-repairing mortar beam loaded with MTS810.22S are carried out in this paper. The main conclusions from the research are as follows:1) According to the self-repairing mechanism, a type of chloroprene rubber adhesive is selected as the repairing chemical on the basis of thorough analysis of the requirements that adhesives must meet.2) Due to the excellent match between glass tube and concrete, glass tube is used as the container of repairing chemicals. So the container of repairing chemicals will break immediately after cracking occurs in concrete or mortar.3) As glass capsules are added as function components, which weaken the mechanical properties of concrete, the influence of the diameter, the length and the volume content of glass capsules on the compressive strength of concrete is tested in this project, which suggests that the optimum length is 25mm, the optimum diameter is 7mm and the optimum volume content is 1.0%--1.5%.4) During the three-point bending test of self-repairing concrete beam with embedded close glass tubes, whether the adhesive can flow out of the glass tubes or not is decided by the combined effect of atmospheric pressure, the forces acted on adhesives by both the walls of glass tubes and concrete cracking surface. Without internally applied pressure, adhesives can't flow out of the glass tubes with one end close and the other one open.5) During the three-point bending test of self-repairing concrete beam with embedded exoteric glass tubes, the mechanical property of concrete beam is restored mostly. And the problems of unclear standards of verifying the self-repairing of concrete cracking, existing in the relevant experiments of other people, are avoided through the appropriate selection of mechanical parameters.6) Because of the shortcoming of the loading with hydraulic jack and the limitation of experiment facilities, the three-point bending test of mortar beams with embedded exoteric glass tubes is conducted with MTS 810.22S machine. The force—cracking opening displacement (COD) curves clearly show that the cracking is fully repaired.