Study Of Factors Influencing The Self-healing Ability Of Concrete

Concrete is wildly used in civil engineering, which plays an important role in construction for its good durability. Concrete belongs to a kind of brittle material, which will produce inevitably local damage because of the influences of physical shrinkage, temperature variation and other adverse external factors. Therefore, if it is not repaired in time, the normal use of the material will be affected and incalculable loss will be caused.In this paper, the factors influencing the self-healing ability of concrete were researched by ultrasonic nondestructive testing, X-ray diffraction analysis and scanning electron microscopy (SEM) analysis test methods. The precast damage of concrete was produced by hydraulic pressure press. The influences of cement particle fineness, dosage, fineness of mineral mixture, water/cement ratio and sand ratio on the self-healing ability of concrete were studied. The influencing rule of components on self-healing ability of concrete was obtained by analyzing the results of experiments. The main results and conclusions of the paper are as follows:1. The influence of fineness of cement on the self-healing ability of cement mortar and concrete were researched. Coarse particles of cement play a certain role in promoting on self-healing of cement mortar and concrete, with the increasing of cement particle size, the self-healing ability of cement mortar increases, but the self-healing ability of concrete increases firstly, and then decreases, 32μm-65μm particles of cement play a very important role in self-healing process of concrete.2. The self-healing ability of cement mortar and concrete show different variation tendencies with the changing of cement particles size. 3μm-32μm particles of steel slag play a very important role in self-healing process of cement mortar and concrete. 32μm-65μm particles of slag can promote the self-healing of the damage of cement mortar and concrete.3. The influence of fineness of different mineral admixture on the self-healing ability of cement mortar and concrete were researched. With decreasing of fineness of steel slag and slag, the self-healing ability of concrete increases firstly, and then decreases, when the surface area of steel slag with coarse particles is 330m~2/kg, the self-healing ability of cement mortar is the strongest, when the surface area of slag with coarse particles is 300m~2/kg, the self-healing ability of cement mortar is the best. When the surface area of steel slag with coarse particles is 330m~2/kg and the dosage is 40%, the growth rate of compressive after self-healing is the highest, and the self-healing ability of concrete is the strongest; when the surface area of slag with coarse particles is 300 m2/kg and the dosage is 40%, the self-healing ability of cement mortar is the best.4. The influence of slag and fly ash, which was added in concrete together, on the self-healing ability of concrete were researched. With the effect of pozzolanic effect, filling effect and secondary hydration effect of slag and fly ash, the self-healing ability of concrete increased. Through the grey relation analysis of factors influencing the self-healing ability of concrete, it can be seen that the influencing extent of various factors was: Fly> slag> cement.5. The influence of water cement ratio and sand ratio on the self-healing ability of concrete was researched. In a certain range of water cement ratio, the self-healing ability of concrete increases with the increasing of water cement ratio, when the water cement ratio of concrete is 0.55, the increases ratio of ultrasonic velocity from damage to self-healing is 23.9%, the increases ratio of compressive strength is 11.1%, and the self-healing ability of concrete is the strongest. When sand ratio is 33%, the increases ratio of ultrasonic velocity from damage to self-healing is 21.9%, the increases ratio is the highest, and the self-healing ability of concrete is the best.