Effects of nano-particles on improvement in wear resistance and drying shrinkage of road fly ash concrete

Nano-materials have been widely applied in cement-based materials due to its excellent performance. Two types of nano-particles, namely nano-SiO2 (NS) and nano-SiC (NC), were employed to prepare nano-modified fly ash cement mortar and road fly ash concrete specimens respectively, and the effects of the nano-particles content on wear resistance and drying shrinkage were studied on the basis of strength test, the mechanisms were then analyzed theoretically. The results indicated that nano-particles could improve the wear resistance of road fly ash concrete, but increase the drying shrinkage. The optimum added dosage of NS for single-doping NS concrete was 2%, and that for NC was 3%. The superior wear resistance of nano double-doped concrete could be found with 2% NS and 2% NC, and meanwhile, the wear loss was only 0.64 kg/m2, with a decrease by 75%; the drying shrinkage rate of the concrete containing 2% NS and 2% NC at 28 d was increased by 124.8% and 85.8%, respectively, compared to the reference concrete. Therefore, it is concluded that due to its surface effect, pozzolanic reaction and microscopic aggregate filling effect, nano-particles have larger surface energy, to change the orientation degree of calcium hydroxide crystals in the interface transition zone and fill pores among cementitious materials, thereby improving the wear resistance and drying shrinkage of fly ash concrete. These results would provide guidance on the design of the high wear resistance and low drying shrinkage fly ash concrete.