Influence of cationic asphalt emulsion on the water transportation behavior and durability of cement mortar

Cement asphalt mortar (CAM) could be considered as the cement mortar modified by asphalt emulsion, which would alter the microstructure of cement mortar and thus exert significant influence on the mechanical properties and durability of CAM. In the current research, the effect of cationic asphalt emulsion on the compressive/flexural strength, flexibility, water adsorption, permeability and sulfate attack of CAM were investigated. The obtained results indicated that, both the compressive strength and flexural strength of CAM all decreased obviously with the increase of A/C (mass ratio of asphalt to cement), on the contrast, the incorporation of cationic asphalt emulsion would improve the flexibility of CAM. The increased A/C would suppress the water transportation, including water adsorption and penetration, into CAM, which is mainly due to the reduction in the pore connectivity and the hydrophobization on the wall of pores, thereby beneficial to improve the durability of CAM. The transportation pathway of water containing sulfate ions into CAM would be inhibited with the increase of A/C, which suppressed the formation of erosion products and in turn decreased the damage of the microstructure of CAM, that is, the incorporated cationic asphalt emulsion would enhance the sulfate attack resistance of CAM. The field emission scanning electronic microscopy (FESEM) observation showed that, with the increase of A/C, more and more asphalt film formed in the CAM, while less and less cement hydration products were generated, which is correlated well with the variation of mechanical properties, water sorptivity and sulfate attack resistance of CAM.