Expansion and degradation of cement paste in sodium sulfate solutions

Expansion and degradation of cement paste in sodium sulfate solutions

Ma, X. (TU Delft Materials and Environment; Shenzhen University)
Copuroglu, Oguzhan (TU Delft Materials and Environment)
Schlangen, E. (TU Delft Materials and Environment)
Han, Ningxu (Shenzhen University)
Xing, Feng (Shenzhen University)

2018

External sulfate attack is a progressive degradation process that may cause expansion, cracking, loss of binder cohesion and increased permeability in cementitious materials. Crystallization pressure theory has often been referred to as the most likely mechanism. However, thus far the stress causing the expansion has not been quantified. In this study, small cement paste pipes with a wall thickness of 2.5 mm were prepared and immersed in sodium sulfate solutions with SO₄²⁻ ion concentrations of 1.5 g/L and 30 g/L. Three types of longitudinal restraints were applied on the specimens before exposure, which were created by a spring, a thin or a thicker stainless steel bar that was centered in the hollow specimens in order to facilitate the non-, low- or high-restraint condition. The free expansion, restrained expansion and generated stress were quantified. The pore size distribution, sulfur distribution and crack pattern were periodically analyzed during the sulfate immersion tests up to 420 days. The generated stresses were found to be as high as 13.1 MPa in high sulfate solution and 8.3 MPa in low sulfate solution under high-restraint condition after 420-day immersion. For the unrestrained specimens immersed in low sulfate solution, an almost uniform sulfur distribution along the diffusion direction was found at 189-day immersion. However, for the unrestrained specimens immersed in high sulfate solution, a layer or several layers of mainly gypsum were formed subparallel to the exposed surface from 133-day immersion.

Crack pattern
Expansion
External sulfate attack
Pore size distribution
Stress
Sulfur distribution

http://resolver.tudelft.nl/uuid:98ab2601-f5ce-490d-9622-f21fe1547b5c

https://doi.org/10.1016/j.conbuildmat.2017.10.026

2022-02-02

0950-0618

Construction and Building Materials, 158, 410-422

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2018 X. Ma, Oguzhan Copuroglu, E. Schlangen, Ningxu Han, Feng Xing