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The filler effect is the most important physical mechanism of mineral admixtures in the early hydration of cement whose chemical properties greatly affect the precipitation of C-S-H. In this study, calcite, strontianite, magnesite, dolomite, quartz, whewellite and whitlockite were selected as the fillers. The morphology and reaction kinetics of synthetic C-S-H precipitated on the surfaces of different fillers were studied via electron microscopy observations and electrical conductivity and ion concentration measurements. The precipitation rate of C-S-H has a positive correlation with the affinity of Ca 2+ for adsorption on the fillers, which can be explained by the nucleation barrier of C-S-H. Extremely ordered honeycomb-like morphology of the C-S-H is found on calcite and strontianite surfaces, while less regular leaf-like or honeycomb-like C-S-H are found on whewellite and whitlockite. The ordered C-S-H pattern is related to the lattice cleavage of the ionic compound filler.In the case of quartz, C-S-H prefers growth along the tangential direction, which is quite different from the normal-direction growth on ionic compounds. The in-plane growth of C-S-H on quartz is believed to be induced by a layer of loosely physically-adsorbed Ca 2+ .

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