Ceramics-Silikáty

The article analyses the effect of the crystalline chemical admixture content on the properties of self-healing concrete. The self-healing concrete properties and the effectiveness of crack sealing were tested. The effect of the crystalline chemical admixture content on the following properties of self-healing concrete were tested: the consistency, density, compressive strength, ultrasonic pulse velocity, water absorption, porosity and freeze-thaw resistance. The self-healing concrete was made of cement, a crystalline chemical admixture, sand, gravel, and water. The crystalline chemical admixture was added from 0 % to 1.5 % by weight of cement. The test results showed that with the addition of the crystalline chemical admixture, the density, ultrasonic pulse velocity, compressive strength, and water absorption decrease, whereas the resistance to the freeze-thaw cycles increases. The analysis of the crack-sealing effectiveness revealed that the formation of crystals started at 14 days of curing, and, at 42 days, the cracks were totally sealed. Therefore, in the presence of the crystalline chemical admixture added at 1.5 % by weight of cement, the self-healing concrete can bridge the cracks as free cement particles hydrate in contact with water and fill the cracks. The obtained self-healing concrete with better durability properties can be used in concrete structures.