Drying of calcium-silicate-hydrates: regeneration of elastic modulus

Dynamic mechanical thermal analysis (DMTA) measurements for layered calcium silicate systems (1·4 nm tobermorite, jennite, synthetic calcium-silicate-hydrate and hydrated Portland cement paste) are reported. Elastic modulus results were obtained for samples initially conditioned to 11% relative humidity (RH) and dried during the DMTA test and for samples subjected to prolonged vacuum and thermal drying prior to a DMTA test. Decreases in elastic modulus relative to the 11% RH starting condition typically observed during a DMTA test were recovered subsequent to the prolonged thermal treatment. A possible ‘regeneration' mechanism for the elastic modulus is discussed. The ‘regeneration' occurs for all the calcium silicate systems studied. The results are consistent with the notions expressed for nanostructural models of calcium-silicate-hydrate in cement paste that comprise structural units based on 1·4 nm tobermorite and jennite.