Concentration and molecular weight of superplasticizer contained in pore solution extracted from hardened cement pastes

Fujita, Hideki*; Haga, Kazuko*; Shibata, Masahito*; Mihara, Morihiro  

There are concerns about the possible increase in the solubility of radionuclides due to the presence of superplasticizers (SP) proposed to be added to cementitious materials in a radioactive waste repository. The concentration and molecular weight of a polycarboxylate type SP in hardened cement pastes has been investigated experimentally in this work. The measurement of total organic carbon in both the pore water extracted from hardened cement pastes by compression and the curing water was performed. A molecular weight of SP in pore water was analyzed to investigate the chemical form. It was found that most SP (more than 90%) remained in the solid phase. Organic substance of a low molecular weight was detected in the pore water by gel permeation chromatography (GPC), possibly due to selective absorption of a high molecular weight part of SP.