Comparison of the chemo-mechanical behavior of low-pH cement exposed to calcareous water and to argillite pore water. (September 2022)

• Record Type: Journal Article
• Authors: Neji, M.; Dauzères, A.; Grellier, A.; Sammaljärvi, J.; Tikkanen, O.; Siitari-Kauppi, M.
• Is Part Of: Applied geochemistry. Volume 144(2022)
• Publication Date: 2022-09
• Subjects: Low pH binder -- Cement paste -- Chemical degradation -- Diffusion -- Microstructure -- Ground water; Environmental geochemistry -- Periodicals; Water chemistry -- Periodicals; Geochemistry -- Social aspects -- Periodicals; Geochemistry -- Periodicals; 551.9
• DOI: 10.1016/j.apgeochem.2022.105392
• Languages: English
• ISSNs: 0883-2927

Abstract

Abstract: This paper focuses on the impact of ground water on the chemo-mechanical behavior of low-pH cementitious materials. Two kinds of ground water are considered, calcareous water and argillite pore water. A sample of low-pH cement paste was immersed for two months in each solution. Chemo-mechanical characterizations (SEM, C-14 PMMA autoradiography, nano-indentation) were performed to estimate the degradation state of the samples. Then, geochemical modelling was performed to validate experimental observations. The decalcification of C–S–H, the dissolution of ettringite and a magnesium enrichment are the main phenomena in both cases. However, we observe a larger and deeper increase of porosity when the calcareous water is in contact with the cementitious material. The chemical modifications linked to the increase of porosity tend to locally decrease the mechanical strength of the cementitious matrix. Highlights: An increase of the porosity linked to mineralogical change appears in low-pH cement paste in contact with ground water. Degradation is divided in three zones: a layer of calcite, a layer of magnesium enrichment and a decalcified zone. The calcareous water is more aggressive than argillite pore water for low-pH cement paste.