Retardation effect of the pozzolanic reaction of low-calcium supplementary cementitious materials on clinker hydration at later age: Effects of pore solution, foreign ions, and pH

T Wang and S Medepalli and YQ Zheng and W Zhang and T Ishida and S Bishnoi and DS Hou and ZG Shi, CEMENT AND CONCRETE RESEARCH, 177, 107416 (2024).

DOI: 10.1016/j.cemconres.2023.107416

Clinker hydration at later age in blended cement pastes was found to be retarded by the pozzolanic reaction of low -calcium supplementary cementitious materials (SCMs). Various mechanisms were explored, including the consumption of pore solution, the presence of foreign ions, and pH -related effects. Experimental results indicated that the dissolution of the foreign ions from SCMs was a secondary effect. The primary cause of the retardation effect was the reduction in pH caused by the pozzolanic reaction. Aqueous precipitation tests yielded the following findings related to pH: (1) At lower pH levels, the precipitation of aluminium -incorporated calcium silicate hydrate(C-A- S-H) gel was reduced due to the decreased nano -adhesion force. (2) The morphology of C-A-S-H gel consisted of small spherical particles at lower pH levels, resulting in a denser capillary pore structure. The latter led to increased water retention within the fine gel pores but a reduced amount of pore solution available in the capillary pores for cement hydration.

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