Heat capacity measurements of cement materials

Sasada, Yuto*; Miyazaki, Yuji*; Nakano, Motohiro*; Matsuo, Yusuke*; Walker, C.*; Sasamoto, Hiroshi; Mihara, Morihiro

no journal, , 

Cementitous materials are to be used in large quantities in the geological disposal of highly radioactive TRU waste. Thermodynamic data on cement hydrate minerals are important to model the long-term dissolution behavior of cement materials during the reaction of these materials with groundwater. Portlandite (Ca(OH)) is a major component (20 to 25 wt%) of hydrated Portland cement. Low temperature heat capacity measurements of three types of portlandite (low purity, high purity, and large crystal) showed purity dependence. The large crystal sample followed Debye's T rule at low temperatures, while the high and low purity samples showed upturn of heat capacity, possibly due to difference in absorbed water vapor and/or calcite (CaCO) contamination. Heat capacities of the cement hydrates (ettringite:Ca(Al(OH))(SO)(HO) and monosulfate:CaAl(OH)(SO)(HO)) exhibited phase transitions associated with the hydration water.