Phase Content of Plasticized Cement Systems in the Early Stages of Heat-Moisture Treatment

Abstract

AbstractThe use of superplasticizers (SPs) in concrete makes it possible to obtain high-strength concretes at the design age. However, their application can reduce the early concrete strength. The use of the latest SPs based on polycarboxylate esters (PCE) allows you to adjust the heat-moisture treatment (HMT) regime. A comparative analysis of the cement stone structure formation was carried out depending on the modification of PCE and sulfonated naphthalene formaldehyde (SNF) under HMT conditions at 60 °C. For the first 2 h of HMT, the amount of C3A and C4AF is greater in the stone with PCE by 12 and 8.5% than in the compositions without additives and 6 and 2% higher than in the compositions with SNF. The introduction of SNF in cement paste leads to an increased content of AFt by 32% compared to a stone with PCE. The content of CaSO4 ⋅ 2H2O in the compositions with PCE was found to be twice as high as in the samples with SNF and without additives for 2 h of HMT. The number of clinker minerals after HMT according to the mode (0 + 6 + 2) h in the stone with PCE is higher than in the compositions without additives and with SNF, but the differences are lower. In general, the results indicate the relaxation of temperature stresses in the cement stone body when PCE is added. Thus, the study indicates the possibility of regulating the HMT modes during the hardening of plasticized cement systems.KeywordsCementHeat-moisture treatmentSuperplasticizerPolycarboxylate esterSulfonated naphthalene formaldehydePhase contentGypsumEttringite