New insights into the effect of calcium formate on hydration process of C3A-AF-Gp System: Formation C3A∙Ca(HCOO)2·11H2O phase

Abstract

• CF and C 3 A form C 3 A∙Ca(HCOO) 2 ·11H 2 O, and the formation process is not affected by Gp and AF. • C 3 A∙Ca(HCOO) 2 ·11H 2 O phase is the main reason for the reduction of 1 d compressive strength of mortar mixed with AF. • Theoretical model of C 3 A∙Ca(HCOO) 2 ·11H 2 O phase formation process was proposed. The effect of calcium formate (CF) on the hydration products of the C 3 A-Gp(gypsum)- alkali-free liquid accelerator (AF) system was researched by XRD, Raman, and SEM. The results showed that CF and C 3 A could form a new C 3 A∙Ca(HCOO) 2 ·11H 2 O phase, and the formation of that the phase was not affected by AF and Gp. Combined with the analysis and test results, a theoretical model of C 3 A∙Ca(HCOO) 2 ·11H 2 O phase formation of the process was proposed. In addition, it was found that CF could promote the dissolution of C 3 S. However, it did not promote the 1 d compressive strength of mortar mixed with the alkali-free liquid accelerator. Analyzed and inferred that the formation of new phase C 3 A∙Ca(HCOO) 2 ·11H 2 O was the main reason for reducing the early strength of mortar. Therefore, it was not recommended to use calcium formate to promote the early strength of mortar mixed with alkali free liquid accelerator.