Effects of pH on the nano/micro structure of calcium silicate hydrate (C-S-H) under sulfate attack

By Xin Liu, Pan Feng, Wei Li, Guoqing Geng, Jiale Huang, Yun Gao, S. Mu, Jinxiang Hong. 2021

147 citations recorded by the source corpus.

Abstract Calcium silicate hydrate (C-S-H), the most important Portland cement hydration product, determines the mechanical properties and durability of cementitious materials. In marine environment, C-S-H often suffers from sulfate attack – one of the most common and severe degradations for concrete. pH is considered as a critical factor in determining the deterioration behavior of C-S-H during sulfate attack, of which the significance may be overlooked. This study focused on the role of pH on the deterioration of C-S-H in terms of the composition and nano/micro structure under sulfate attack. The results show that lowering pH aggravates the decalcification of C-S-H, whereas a strong alkaline condition is beneficial to increase the resistance to deterioration. An increase in the mean chain length together with the proportion of large pores (>10 nm) is observed when C-S-H is subjected to low-pH sulfate attack (pH = 10–12), resulting in a relatively loose structure. The deep analysis on defective tobermorite model reveals that calcium at the interlayer of C-S-H nanostructure is readily removed under sulfate attack, thereby improving the potential of Si-O-Si groups formation and increases the mean chain length of C-S-H.

Subfields: Civil and Structural Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/4d823b3dd8e9dac6de7addcacd5871c8226c05f6