Calorimetric study on the influence of redispersible E/VC/VL terpolymer on the early hydration of Portland cement

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.

Rejuvenation, embryonic shear bands and improved tensile plasticity of metallic glasses by nanosecond laser shock wave

“…Different from polymer dispersions, the cement mineral grains take positive charges, which tend to be covered with polymer particles due to the ionic bonding effect. The polymer coverage layer reduces the interaction between cement minerals and water and finally inhibits the early hydration [14,23,31]. As a consequence of delayed initial hydration of polymer-modified CSA cement, the formation of ettringite at 1 h is significantly retarded while small amount of dihydrate was detected.…”

“…The effect of polymer dispersions on the hydration of Portland cement has been well disclosed from previous studies [13][14][15][16][17][18][19][20]. Generally, the addition of polymer dispersions would retard the hydration of ordinary Portland cement (OPC) [20][21][22][23][24][25][26][27][28][29][30], and this retardation effect becomes much more significant when the bigger polymer content was dosed [31,32]. It has been widely accepted that its retardation effect is mainly attributed to their adsorption onto the surface of the cement grains and their complexing effects with Ca 2?…”

“…The negatively charged polymer dispersions can be attracted by cement grains surface with heterogeneous charge distribution, driven by the electrostatic force. The adsorbed polymer layer will hinder the cement hydration by acting as a diffusion barrier layer to suppress the diffusion of water and ions between the mineral phase and aqueous phase [14,23], thus prolong the induction period and decrease the hydration rate [31]. Meanwhile, the addition of polymer dispersions in cementitious system could decrease the concentration of free Ca 2? in cement pore solution through complexation effect between polymers and Ca 2? , thus, the nucleation rate of calcium silicate hydrates (C-S-H) and the precipitation rate of Portlandite are retarded, and finally, the induction period can be prolonged [14,33].…”

Quantitative Analysis of the Calcium Hydroxide Content of EVA-Modified Cement Paste Based on TG-DSC in a Dual Atmosphere

“…Hardened cement paste is a composite material whose properties ultimately depend on the components and their spatial relationship to each other. Calcium silicate hydrate (C-S-H) gel, Ca(OH) 2 , ettringite (AFt), and monosulfoaluminate (AFm) are important hydrated products and components of hardened cement pastes [ 1 , 2 , 3 , 4 , 5 ]. They play a crucial role in the various behaviors of hardened cement paste, such as strength and durability.…”