Experimental study on evaluation of self-healing capability of FRCCs comprising different components

Fiber reinforced cementitious composite (FRCC) has a great capability for selfhealing of cracks. Concrete cracks with a sufficiently small crack width (below 0.1 mm) can be closed and self-healed by crystallization of calcium carbonate in the presence of moisture, even in the case of ordinary concrete. Such precipitation is caused by reaction of calcium ions and dissolved carbon dioxide. FRCC can accelerate the self-healing process mainly due to two characteristics, i.e., crack widths can be restricted to be narrow, and fibers bridging cracks can act as a core for precipitating chemical products. Previous research by the authors showed that some types of reinforcing fibers with polar groups, such as polyvinyl alcohol (PVA) with a hydroxy group, can induce a greater precipitation volume for calcium carbonate crystals around themselves than fibers without polarity, such as polypropylene (PP). In this study, a fundamental experiment was performed in order to specify the FRCC component materials that can enhance the self-healing effect. FRCCs with different types of reinforcing fibers (PVA and PP), aggregates, and admixtures (silica sand, limestone sand, and limestone powder) were subjected to the precipitation test\u97the volume of the precipitated calcium carbonate crystals around each fiber and on the crack surface of FRCC specimens was measured in order to estimate the selfhealing capability. Specimens with a crack surface were immersed for 7 days in a small water tank. The results showed that limestone sand and powder did not strongly affect the quantity of crystal precipitation around the exposed fiber; however, they enhanced the crystal precipitation area on the crack surface (flank). A large amount of precipitated crystal on the crack surface might enhance the self-healing function of FRCCs