Effects of surface-modified coal-bearing metakaolin and graphene oxide on the properties of cement mortar

Abstract

The environmental impact of concrete can be limited by using supplementary cementitious materials (SCMs) and nanomaterials. After calcination, coal-bearing kaolinite can be transformed into coal-bearing metakaolin (CMK), which can be used to substitute cement. This study aims to study the combined effects of CMK and graphene oxide (GO) on the mechanical properties of cement mortar. For improving its dispersion, the CMK was modified to be positively surface charged mCMK, which was demonstrated by using zeta potential measurement. According to UV–Vis results, GO dispersion is also better when mCMK was used. By adding both mCMK and GO, the flexural and compressive strength of cement mortar at 28 days were improved 47.24% and 33.89%, respectively, compared to blank cement mortar. The improvement of mechanical properties can be attributed to more sufficient cement hydration and pore structure refinement, which is contributed by pozzolanic reaction of mCMK and beneficial effects of GO. The synergistic effect of using both mCMK and GO can also be confirmed by comparisons between different cement mortar samples. This study sheds light on the application of CMK and GO as promising SCMs and nanomaterial to be used with cement.