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Expansion and degradation of cement paste in sodium sulfate solutions
- Source :
- Construction and Building Materials, 158
- Publication Year :
- 2018
- Publisher :
- Elsevier BV, 2018.
-
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.
- Subjects :
- Expansion
Materials science
Gypsum
Sulfur distribution
0211 other engineering and technologies
chemistry.chemical_element
02 engineering and technology
engineering.material
Stress
law.invention
chemistry.chemical_compound
law
021105 building & construction
Sodium sulfate
Free expansion
General Materials Science
Crystallization
Composite material
Sulfate
Civil and Structural Engineering
Building and Construction
Pore size distribution
021001 nanoscience & nanotechnology
Crack pattern
Sulfur
Cracking
chemistry
engineering
External sulfate attack
Cementitious
0210 nano-technology
Subjects
Details
- ISSN :
- 09500618
- Volume :
- 158
- Database :
- OpenAIRE
- Journal :
- Construction and Building Materials
- Accession number :
- edsair.doi.dedup.....5cff1e4c2c00dba5da0a29fc0c5af6a2