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Preparation and properties of a new alkali free liquid accelerator for Shotcrete

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Document pages: 9 pages

Abstract: A new type of alkali free liquid accelerator for shotcrete was developed. The setting time, strength and shrinkage properties of two kinds of Portland cement with accelerator were studied in detail. In addition, the accelerating mechanism of alkali free liquid accelerator and the hydration process of shotcrete are also discussed. The results show that the alkali free liquid accelerator significantly shortens the setting time of cement paste, in which the mass fraction of 8   accelerator is about 3   the final setting time is about 7 minutes   the minimum compressive strength of cement mortar using the accelerator can reach 23.4   MPA on the first day, which is 36.2 higher than that of cement mortar without acceleratorretention rate of 28-day compressive strength reached 110 . In addition, the accelerator still shows a good accelerating effect under low temperature conditions. However, the shrinkage rate of the concrete increased with the amount of the accelerator. 5~8 content of accelerator is recommended for shotcrete in practice. XRD and SEM test results showed that the alkali-free liquid accelerator promoted the formation of ettringite crystals due to the increase of Al3+ and concentration.

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