Abstract
• Calcium bromide was used to improve the early strength of mortar mixed with alkali free liquid accelerator. • It is proved that Ca 4 Al 2 O 6 Br 2 ·10H 2 O phase is the main reason to promote the early strength of mortar. • A theoretical model of the synergistic effect of calcium bromide and alkali free liquid accelerator is proposed. This paper investigated the influence mechanism of CaBr 2 on the early strength of mortar mixed with the alkali-free liquid accelerator. The results showed that the final setting time was shortened from 6.5 to 5.58 min, and the compressive strength of 1 d, 3 d, and 7 d increased by 42.7%, 28.96%, and 32.47%, when the dosage of CaBr 2 was 1.5%. Meanwhile, the hydration products were further investigated in CaBr 2 -C 3 A-H 2 O, CaBr 2 -C 3 A-Gp-H 2 O, and CaBr 2 -C 3 A-Gp-AF-H 2 O systems. By XRD and Raman analysis, it was determined that CaBr 2 could form a new phase Ca 4 Al 2 O 6 Br 2 ·10H 2 O with C 3 A in different systems. Combined with the setting time and the compressive strength test results, it was concluded that Ca 4 Al 2 O 6 Br 2 ·10H 2 O phase was the main factor in improving the early strength and shortening the setting time. Moreover, a conceptual model of CaBr 2 hydration was proposed to analyze the hydration process.
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