Influence of Some Soluble Polymer Admixtures on the Hydration and Strength Development of Portland Cement Pastes

Hardening of cement pastes modified with 1 % polymers as methyl cellulose (MC), hydroxyl ethyl cellulose (HEC) and polyvinyl alcohol acetate (PVAA) comprises cement hydration and polymer effect on physicochemical and mechanical features of the modified cement pastes. Results showed that the water/cement ratio and setting times largely declined with polymers, where the values of water of consistency are 28.55, 25.69, 25.12 and 24.95 %, respectively. The initial setting times are 142, 134, 133 and 132, while the final setting times are 190, 185, 183 and 181 min., respectively. The incorporating of these polymers improves and enhances the bound water contents, bulk density, and compressive strength at 90 days curing, where the bound water contents are 13.26, 14.55, 14.73 and 15.29 %, the bulk density are 2.0369, 2.0413, 2.0421 and 2.0563 g/cm3 and the compressive strength are 62.23, 64.13, 65.25 and 68,71 MPa, respectively. The apparent porosity gradually declined as 22.12, 21.36, 20,84 and 18,82 %, respectively. The free lime contents are also diminished as 7.55, 6.18, 6.65 and 4.61 %, respectively. The rate of hydration was retarded at early ages of hydrating, while was improved and enhanced at the later ages. The obtained results are confirmed with Isothermal Calorimetry, thermal analysis, and FT-IR spectra. Despite the early reduction of the hydration reactions, a higher grade of hydration is observed after 90 days of hydration for the modified cement pastes according to the better dispersion of the cement grains during mixing and casting.