Self-healing properties of reactive powder concrete with nanofillers

The study presented in this paper aims to investigate the self-healing properties of reactive powder concrete (RPC) modified with nanofillers, which has the self-healing ability of compressive and flexural strength. The inner damage of RPC with nanofillers during loading is analyzed by using an acoustic emission system. Three types of nanofillers (nano-SiO2, nano-TiO2 and nano-ZrO2) and two curing methods (water curing and air curing) are selected for identifying the influencing factors. Experimental results indicate that all incorporated nanofillers have the ability to enhance the self-healing ability of RPC. However, we noted that the enhancement is more evident when the RPC is cured in water. Composite with nano-SiO2 has the largest self-healing coefficients of compressive (C-s) and flexural strength (F-s) with water curing of 1.31 and 1.19, which increases by 39.4% and 33.7% compared to RPC without nanofillers, respectively. The incorporation of nanofillers weakens and even eliminates the Kaiser effect of RPC under secondary loadings, indicating that to a certain extent, crack healing has taken place. The effect of the nanofiller modification mechanisms on the RPC self-healing properties is thought to be attributed to three main features: (1) the provision of nanofillers provides the hydration environment for unhydrated cement particles and nucleation sites for the hydration products; (2) nanofillers improve the 3D network structure of concrete matrix, produce more fine cracks and disperse the propagation direction of the cracks; (3) the pozzolanic reaction of nanofillers (including nano-SiO2 and nano-TiO2), especially for nano-SiO2, produces additional calcium silicate hydration, and increases the compactness of RPC.