Expansion and degradation of cement paste in sodium sulfate solutions

Xu Ma, Oguzhan Copuroglu, Erik Schlangen, Ningxu Han, Feng Xing

Research output: Contribution to journalArticleScientificpeer-review

12 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)410-422
Number of pages13
JournalConstruction and Building Materials
Volume158
DOIs
Publication statusPublished - 2018

Keywords

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

Fingerprint Dive into the research topics of 'Expansion and degradation of cement paste in sodium sulfate solutions'. Together they form a unique fingerprint.

  • Cite this