Influence of mass content of in-situ formed aragonite on the mechanical strength and pore structure of γ-C2S carbonation

To reveal which one of the aragonite and calcite is more beneficial to the performance of calcium silicate carbonation materials, this paper mainly investigated the effects of in-situ formed aragonite with different mass contents on the mechanical strength and pore structure of γ-C2S carbonation materials. The results indicated that the mass contents of aragonite formed in-situ in γ-C2S carbonated pastes could be regulated by adjusting the amount of the crystal regulating agent triethanolamine (TEA). Furthermore, the flexural strength and compressive strength of the γ-C2S mortar specimen with aragonite mass content of about 67 % increased by 64.9 % and 57.3 %, respectively, the total porosity decreased by 29.2 %, and the most probable pore size reduced from 1.34 μm to 0.67 μm, all compared with the reference mortar specimen with cubic calcite after 7 d of carbonation. The analysis results of microscopic morphology and pore structure parameters indicated that needle-like aragonite, in contrast to cubic calcite, grew from the nucleation site into surrounding pores, which was more conducive to reducing the porosity of the mortar specimen, and it subdivided macropores into smaller units, thus reducing both the number of macropores and the pore size. Therefore, the formation of aragonite can significantly enhance both its flexural and compressive strengths, particularly its flexural strength. These findings indicate that aragonite is more advantageous than calcite with regard to the performance of carbonation materials, thereby providing new insights for the structural optimization of the materials. •In-situ aragonite formation enhanced flexural strength and compressive strength of γ-C2S mortar.•In-situ aragonite formation altered pore structure of γ-C2S mortar.•In-situ aragonite formation improved the microstructure of γ-C2S mortar.•Different mass contents of aragonite affect the mechanical properties and pore structure.