Title:
Thermodynamic Modeling of Chemical Acidification of Cementitious Paste (Prepublished)
Author(s):
Feyza Nur Sahan, W. Jason Weiss, O. Burkan Isgor
Publication:
Materials Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
acid attack; C S H; limestone; portland limestone cement; supplementary cementitious materials; thermodynamic modeling
DOI:
10.14359/51749035
Date:
7/10/2025
Abstract:
The role of limestone (LS) powder replacement and changes in C-S-H due to pozzolanic reactions on the acid resistance of cementitious pastes are studied using thermodynamic modeling. Simulations are performed under equilibrium conditions while hydration products were exposed to increasing levels of sulfuric acid. LS replacement doesn’t show sacrificial characteristics against sulfuric acid attack, and LS acidification starts only after full consumption of portlandite, and most C-S-H. Increased LS replacement causes the dilution of the formed portlandite and C-S-H volumes, which results in their full consumption at lower acid concentrations than mixtures without LS replacement. Pozzolanic reactions of SCMs result in C-S-H phases with lower Ca/Si than OPC-only counterparts, increasing acid resistance. However, highly reactive and/or high-volume SCM replacements might further decrease the available portlandite, reducing the buffer acid resistance capacity. This issue is particularly critical for portland limestone cement-based systems.