Hydration of ordinary Portland cement/high alumina cement pastes containing phosphonate compounds

Abstract

<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-bidi-theme-font:minor-bidi;="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">The hydration process of ordinary/Portland cement (OPC)-high alumina cement (HAC) paste systems with and without the phosphonate compounds, aminotri (methylene-phosphonic acid) (AlMP), 1 hydroxyethylidene-1, 1-diphosphonic acid (HEDP) and diethylenetriaminepenta (methylene-phosphonic acid) (DTPMP), was investigated using conduction calorimetric and impedance measurements. Conduction calorimetry provides relevant data on the heat development characteristics of the cement hydration reactions and the impedance spectroscopy characterizes changes in the microstructural development and ionic concentration of the pore solution resulting from the hydration reactions. The presence of 0.05% phosphonate has little effect on the OPC/HAC paste system. At the 0.2% level, a reduction in the rate of heat evolution is observed. This indicates that the phosphonate compounds interfere with the gypsum-cement reactions especially in the pastes containing 0.2% ATMP and HEDP resulting in Portland cement hydration (mainly the C₃S and C₂S phases) retardation in an OPC/HAC blended system.</span>