Investigation of micro-structure and compression behavior of cement mortar with artificial geopolymer sand

An artificial alternative material for natural sand in construction is of significance for the civil engineering. In the present study, the effects of artificial geopolymer sand (AGS) as an alternative to natural sand (NS) on pore structure and mechanical property of cement mortar were studied. First, six groups of cement mortar specimens were prepared with the different replacement ratios (0.0%, 20.0%, 40.0%, 60.0%, 80.0% and 100.0%). Then, a series of nuclear magnetic resonance (NMR) tests were performed to study the effects of replacement ratio on the density, total porosity and percentage of different size pores. Finally, the ultrasonic wave and uniaxial compressive tests were performed to study the effects of replacement ratio on the P-wave velocity, strength and elastic modulus. The results show that the density and P-wave velocity decrease linearly as the replacement ratio increases. The total porosity increases slowly at first and then increases rapidly as the replacement ratio in-creases. The increase in replacement ratio induces the more significant increase in the smaller pores compared with the larger pores. The strength and elastic modulus firstly increase and then decrease as the replacement ratio increases. The strength and elastic modulus decreased by 11.0% and 5.4% when replacement ratio reaches 100%.