Self-healing concrete

Concrete is used in the construction industry worldwide. However, concrete is generally brittle and easily cracked, especially under a tensile force. Moreover, in order to reduce the amount of sand used, it has been attempted to use waste rubber to replace sand. However, adding rubber reduces the mechanical properties. Thus, a fiber called Duras EasyFinish has been used to attempt to offset the negative influence from adding rubber. In this chapter, specimens with standardized and natural cracks are tested to inspect the self-healing abilities when different fiber contents are added to concrete. Tests proved that mechanical properties increase to the highest value when 0.2% fiber is put in concrete. This can be explained by the fact that the fiber combines cracks to improve the strength of concrete. Moreover, ultrasonic pulse velocity results of specimens with standardized cracks show very low self-healing increase rates, which fluctuate from 0.1% to 1%. This chapter reveals the reason for low self-healing increments, which is that fiber is merely added as an element in concrete instead of bonding. Self-healing increase rates of specimens with natural cracks increase from around 3.25% to 3.5% between 30 days and 36 days, then the values fall within the next 6 days. The natural frequency test is another indicator for measuring the self-healing abilities of concrete. Natural frequencies of specimens with different depths of cracks are also highlighted in this chapter.