Study on Physical Properties of Cement Pastes Modified with HPMC and EVA

摘要

Cellulose ethers and redispersible polymer powders are common admixtures in dry-mixed mortars. The researches on mechanical properties of hydroxypropylmethyl cellulose (HPMC) and ethylene-vinyl acetate redispersible polymer powder (EVA) in cement pastes are still needed. Different from early researches that the mixing amount of HPMC in mortars being about 0.5%, properties of mortars with mixing amount of HPMC from 0 to 5‰ at constant of EVA were studied. It is shown that when the W/C increases at constant of the HPMC/C and the EVA/C, the setting time and fluidity increase while the compressive strength decreases. When the EVA/C increases by keeping the W/C and the HPMC/C constant, the compressive strength decreases while the fluidity and setting time increase. Keep the W/C and the EVA/C constant, the fluidity and the compressive strength decreases while initial setting time and final setting time increase when the HPMC/C increases. Linear positive correlation is found between the setting time of cement pastes and the HPMC/C, while logarithmical correlation is found between the fluidity of cement pastes and the HPMC/C. When the HPMC/C is less than 1.2 ‰, the setting time increases slowly, the fluidity decreases quickly, while the compressive strength decreases slowly. When the HPMC/C is higher than 1.2 ‰, the setting time increases quickly, the fluidity decreases slowly, while the compressive strength decreases quickly.