Microstructures and mechanical properties of polymer modified mortars under distinct mechanisms

In this study, two types of acrylic latexes, PA (polyacrylate) and PU/PA (polyurethane modified PA), are investigated in their influences on mechanical properties of mortar under different interaction mechanisms. In light of a previous study, the polymer-cement hydrates interaction mechanisms in PA and PU/PA modified mortars are illustrated respectively, and the microstructures are simulated using a computer model. Through mechanical experiments, it is revealed that the incorporation of polymer tends to reduce the compressive strength and elastic modulus except PA at low P/C ratio, while improve the flexural strength and toughness. As compared with PA, PU/PA is more effective in these influences. All of the influences of PA and PU/PA on mechanical properties can be explained successfully based on the interaction mechanisms and microstructures. In addition, it's also found that the compressive strength of polymer modified mortar can be roughly estimated based on a modified gel/space ratio, and the incorporation of polymers does not change the relationship between elastic modulus and compressive strength. A high-temperature curing procedure is concluded to be suitable for preparation of high-performance cement composites in short period.