Abstract
The effects of redispersible ethylene–vinyl chloride–vinyl laurate terpolymer (E/VC/VL) on the early hydration evolution of Portland cement were quantitatively investigated by isothermal calorimetry, setting time testing, thermal analysis, Fourier transform infrared spectroscopy, X-ray diffraction analysis and environmental scanning electron microscope analysis. The results show that the E/VC/VL definitely affects the early hydration process of cement paste, increases the initial exothermic peak value, decreases the heat evolution rate of the acceleration period and the second hydration exothermic peak, but increases the heat evolution rate during the deceleration period. And the E/VC/VL has little effects on the length of these different hydration periods. The E/VC/VL decreases hydration heat and hydration degree within 72 h, and the bigger the E/VC/VL dosage is, the less hydration heat and hydration degree are. The E/VC/VL retards the formation of hydrates, decreases the content of Ca(OH)2 and CSH gels, affects the morphology evolution of hydrates and declines the crystalline degree and crystal size of Ca(OH)2. Besides, the E/VC/VL retards the formation of AFt and inhibits the conversion of AFt to AFm, accordingly keeping AFt content higher at later hydration time. In addition, no new phases are formed in cement paste with the E/VC/VL. The retardation of E/VC/VL is also evidenced by the setting time of cement pastes. But with hydration time prolonging, the retardation of E/VC/VL on cement hydration gradually weakens.
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