The Influence of Methylcellulose on the Hydration Process of C3S, C3A and Mixture of these Phases

The paper presents the results of investigation over influence of 0.3% addition of hydroxypropyl methylcellulose (MC) of 40 and 70 Pa·s viscosity on the hydration process of main clinker phases: C3S and C3A and also their mixture, both in presence and absence of gypsum.During the research it has been indicated that methylcellulose inhibits the hydration process of clinker phases, analyzed both separately and in their mixture. Moreover, presence of that additive reduces reactivity of calcium sulphatedihydrate what leads to formation of decreased amounts of ettringite. No significant differences resulting from viscosity of used methylcellulose were observed. Investigation over the influence of that admixture on the hydration process of tricalcium aluminate indicated that addition of methylcellulose inhibits hydration process of C3A with water. Similar influence of that admixture was observed in the case of C3A hydration in presence of gypsum. A lot of gypsum remains in the reaction mixture. Little amounts of ettringite are forming, however, there is no monosulphate. Inhibition of sulphate ions reaction with C3A is slightly higher in the case of methylcellulose of higher plastic viscosity.Also in the hydration examinations of tricalcium silicate methylcellulose addition caused a retardation of alite reaction with water. In first hydration hours of alite with MC addition there were no peaks of portlandite in the XRD pattern. In the presence of gypsum the influence of methylcellulose addition on the hydration course was significantly weaker. Simultaneously no significant differences related to the influence of different plastic viscosity of methylcellulose were observed.Similar course of reactions was observed in the case of hydration of alite and tricalcium aluminate mixture in the presence of gypsum and methylcellulose. After one week of hydration significant amounts of unreacted gypsum are still remaining. However, little amounts of ettringite are created.