Early Hydration of Tricalcium Silicate

Abstract

The hydration of tricalcium silicate (C3S) in the preacceleration stages was studied. The C3S particles carry a positive charge during the early stages of hydration. Following a rapid hydrolysis of C3S, calcium ions adsorbed on the Si-rich surface of C,S particles, greatly reducing their further dissolution, thus initiating the induction period. The [Ca"] and [OH-] continue to increase at lower rates and, because Ca(OH), crystal growth is inhibited by silicate ions, become supersaturated with respect to Ca(OH),. When the supersaturation reaches a value of == 1.5 to 2.0 times the saturation concentration, nuclei are formed, and rapid growth of Ca(OH), and C-S-H is initiated. These products act as sinks for the ions in solution, thus enhancing the further dissolution of C3S.

Effect of magnesium/calcium ratios in solutions treated by electrodialysis: Morphological characterization and identification of anion-exchange membrane fouling

“…In spite of the recirculation and basic conditions of concentrate in contact with the AEM, the cation concentration was never sufficient to induce crystallization on this membrane interface. As suggested by many authors, for crystallization to occur, spontaneous nucleation and precipitation were due to supersaturation [22,25]. Hence, for R = 1/5 and up, the condition of nucleation would be indirectly affected by the significant fouling of the cation-exchange membranes.…”

Effect of partially hydrated cementitious materials on early-age shrinkage of ultra-high-performance concrete

“…Several authors have claimed that the addition of pre-hydrated C 3 S reduces the induction period and accelerates the hydration process as it provides nucleation sites for further hydration product formation (Odler and Dörr, 1979;Soliman and Nehdi, 2011b). Moreover, added CH crystalline acts as a sink for calcium and silicate ions in the solution, enabling further dissolution of C 3 S and renewed CSH formation (Tadros et al, 1976). This is depicted by the DSC results in Figure 4, where enthalpies of CH for the PHCM mixture were significantly higher than that for the control mixture over the investigated period.…”

The Developing Microstructure in Portland Cement

“…Several studies [80][81][82][83][84][85][86][87] have been carried out on relatively dilute systems and although data during the first minutes is difficult to obtain, the concentration of Ca ++ appears to rise more rapidly in less dilute systems [81,82], at higher temperature [82], and with increasing reactivity [83], Degree of agitation and particle size influence the solubility of lime [88] and these trends might also be observed for C 3 S. Similarly, the concentration of 0H~ ions rapidly increases during the early stages [85]. The pH rises to a value of about 12.5 [84,89] within minutes and remains constant for hours.…”

“…Electrophoretic mobility measurements [81 ] indicate that C 3 S particles become positively charged during the early stages, zeta potential = ^+23 mV. Indeed, with rising pH many polyvalent metal ions, including calcium, can increasingly adsorb on silica [101] until the metal hydroxide is nucleated.…”