Experimental study on the effect of carbon nanofiber content on the durability of concrete

Abstract

To study the effect of carbon nanofiber (CNF) content on the durability of concrete, the shrinkage test, freeze-thaw cycle test, penetration test and carbonation test of carbon nanofiber reinforced concrete (CNFC) with different volume fractions (0.1%, 0.2%, 0.3%, 0.4%, 0.5%) were carried out. In addition, the microscopic modification mechanism of carbon nanofibers (CNFs) to the durability of concrete was further explored by SEM test and MIP test. The results show that the microstructure of concrete can be improved and the pore structure can be refined by CNFs in two ways which are fiber bridging and pore filling, significantly improving the durability of concrete. The incorporation of appropriate amount of CNFs can significantly reduce the shrinkage rate, mass loss rate, compressive strength loss rate, seepage height, relative permeability coefficient and carbonation depth of concrete. When the volume fraction of CNFs is 0.3%, all the above indexes of CNFC are the smallest, therefore, the shrinkage resistance, frost resistance, carbonation resistance of CNFC are the best and the permeability is the lowest, which shows CNFC with a volume fraction of 0.3% performs the best durability. When the volume fraction of CNFs is more than 0.3%, the modification effect of CNFs on the durability of concrete is reduced, but the shrinkage resistance, frost resistance, and carbonation resistance of CNFC with a volume fraction of 0.5% are still evidently better than those of plain concrete (PC) and the permeability of it is lower than that of PC.