HYDRATION OF ORDINARY PORTLAND-CEMENT HIGH-ALUMINA CEMENT PASTES CONTAINING PHOSPHONATE COMPOUNDS

The hydration process of ordinary/Portland cement (OPC)-high alumina c ement (HAC) paste systems with and without the phosphonate compounds, aminotri(methylene-phosphonic acid) (ATMP), 1-hydroxyethylidene-1, 1-d iphosphonic acid (HEDP) and diethylenetriaminepenta (methylene-phospho nic acid) (DTPMP), was investigated using conduction calorimetric and impedance measurements. Conduction calorimetry provides relevant data on the heat development characteristics of the cement hydration reacti ons and the impedance spectroscopy characterizes changes in the micros tructural development and ionic concentration of the pore solution res ulting 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 r eduction in the rate of heat evolution is observed. This indicates tha t the phosphonate compounds interfere with the gypsum-cement reactions especially in the pastes containing 0.2% ATMP and HEDP resulting in P ortland cement hydration (mainly the C3S and C2S phases) retardation i n an OPC/HAC blended system.