Influence of Some Soluble Polymer Admixtures on the Hydration and Strength Development of Portland Cement Pastes
Keywords:Cement, Polymer, Admixture, Setting, Density, Strength, Microstructure, FTIR, SEM
Hardening of cement pastes modified with 1 %polymersas methyl cellulose (MC), hydroxyl ethyl cellulose (HEC)and polyvinyl alcohol acetate (PVAA) comprises cement hydration and polymer effect on physicochemical and mechanical featuresofthe modified cement pastes.Results showed thatthe water/cement ratioandsetting times largely declined with polymers, where the values of water of consistencyare 28.55, 25.69, 25.12 and 24.95 %, respectively. The initial setting timesare 142, 134, 133 and 132, while the final setting timesare 190, 185, 183 and 181 min., respectively.The incorporating of these polymers improves and enhances the bound water contents, bulk density,and compressive strength at90 days curing, wherethe bound water contents are13.26, 14.55, 14.73 and 15.29%,the bulk density are 2.0369, 2.0413, 2.0421 and 2.0563g/cm3and the compressive strength are62.23, 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 withIsothermal Calorimetry, thermalanalysis,andFT-IR spectra. Despitethe early reduction of the hydration reactions, a higher gradeof hydration is observedafter 90 days of hydration for the modified cement pastesaccording to the better dispersion of the cement grainsduring mixing and casting.
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