Magnesium silicate hydrate formation at the surface of hydrated cements

B. Lothenbach, E. Bernard, Wolfgang Kunther, K. De Weerdt

Research output: Contribution to conferencePaperResearchpeer-review

Abstract

At the interaction zone of hydrated cements with seawater or with clayey rocks, leaching, carbonation, decalcification of C-S-H as well as the formation of magnesium silicate hydrates (M-S-H) is observed. The formation of M-S-H is related to the relatively high magnesium concentrations (3-60 mmol/L) in seawater as well as in the interstitial solution of clayey rocks and the lowering of the pH at the leached surface of the cement. Leaching and carbonation decrease the pH at the surface and destabilise C-S-H, which accelerates M-S-H formation. The direct study of the properties of M-S-H at surface of hydrated concrete in contact with seawater or clays is complicated by the very poor crystallinity of M-S-H and the presence of other minerals.
Detailed studies on synthetic M-S-H indicated that M-S-H has a sheet silica structure similar to clay minerals and contains in addition to magnesium and silica, also some aluminium, calcium and alkalis. Thermodynamic modelling indicated that conditions which favour leaching of C-S-H ease the formation of M-S-H at the surface of mortars and concretes. Thermodynamic modelling was also able to highlight the sequence of chloride, sulfate and magnesium accumulation observed at the surface of mortar exposed to seawater.
Original languageEnglish
Publication date2019
Number of pages8
Publication statusPublished - 2019
Event2nd RILEM Spring Convention & International Conference on Sustainable Materials, Systems and Structures - Lone Hotel, Rovinj, Croatia
Duration: 18 Mar 201922 Mar 2019
Conference number: 2

Conference

Conference2nd RILEM Spring Convention & International Conference on Sustainable Materials, Systems and Structures
Number2
LocationLone Hotel
CountryCroatia
CityRovinj
Period18/03/201922/03/2019

Keywords

  • Magnesium silicate hydrate (M-S-H)
  • Deterioration
  • Leaching
  • Seawater

Cite this

Lothenbach, B., Bernard, E., Kunther, W., & De Weerdt, K. (2019). Magnesium silicate hydrate formation at the surface of hydrated cements. Paper presented at 2nd RILEM Spring Convention & International Conference on Sustainable Materials, Systems and Structures , Rovinj, Croatia.