Influence of organosilicon admixtures on the hydration of Portland cement

Abstract

The impact of three different organosilicon compounds: poly(dimethylsiloxane) (PDMS), potassium methylsiliconate (MESI) and triethoxyoctylsilane (OTES), used as integral admixtures, on Portland cement hydration has been investigated by isothermal calorimetry and DTA-TG analysis. The silicon-based compounds are widely used as internal hydrophobic agents added into batch water; therefore, their effectiveness was investigated by means of capillary water absorption test. The isothermal calorimetry was used to measure the rate and amount of heat released during ordinary Portland cement hydration with integral organosilicon admixtures at 20 °C, 30 °C, 40 °C and 50 °C. It allowed to determine the activation energy as well. The results indicate that used admixtures (except MESI admixture) decrease in the rate and amount of heat release during cement hydration. In addition, it is noticeable that the addition of MESI admixture significantly prolongs the induction period and delays hydration. In contrast to MESI and OTES admixtures, PDMS-based admixture does not affect significant on the activation energy. DTA-TG analysis had shown differences between reference sample and samples containing organosilicon admixtures during thermal decomposition, in terms of the amount of moisture and bound water, as well as Ca(OH)2 or carbonates. The results presented in this paper enable a better understanding of the interactions between the organosilicon integral admixtures and the cement matrix. The study shows the effect of integral admixtures on cement hydration and thus the potential effect on the final properties of the cement-based material.

Influence of silanes on the hydration of cement by separating the cement into its individual phases

“…The polycondensation rate of nOTES is even lower and has no detectable effect on hydration. The observation of hydration retardation by silanes in the early hours has already been described by several authors [9,10].…”

The influence of internal hydrophobization using organosilicon admixture on the performance and the durability of concrete

“…The lower concentration, equal to 0.8%, is recommended by the product manufacturer. The second dosage was selected based on conducted research, the results of which were published in (34). The application of 3% of hydrophobic admixture per cement mass significantly reduced the amount of absorbed water when compared with the specimens containing 1% and 2% of admixture.…”

Effect of alkali-silica treatments of miscanthus fibres on chemical and micro-morphological modifications

“…Sodium silicate can contribute to increase the strength of mineral binders (lime-cement) due to the reaction with residual calcium hydroxide and consequent production of further binding C-S-Hs. However, some sources of silica, including siloxanes, and silanes, part of the organosilicon family, exhibit hydrophobic properties that can interfere with the reaction chemistry of mineral binders (Grabowska and Koniorczyk, 2022).…”