Abstract
The surface structures of entrained air voids in hardened cement paste were examined by means of an environmental scanning electron microscope (ESEM). Three different pure anionic surfactants were used: sodium dodecyl sulfonate (SDS), sodium dodecyl-benzene sulfonate (SDBS), and sodium oleate (SO). It was observed that a distinct shell forms around most of the entrained air voids regardless of the surfactant used. It was also shown that some hydration products can grow into the air voids at very early ages and may fill considerable amount of the void volume. In addition to the microscopic evaluation, a modified foam index test and surface tension measurements were also conducted on the solutions with different mixtures. It was determined that since oleate molecules coming from SO were precipitated in the mix as calcium oleate, exiguous amount of air bubbles were stabilized in the paste; however, when SDS and SDBS were used, an acceptable amount of air bubbles were stabilized.
| Original language | English |
|---|---|
| Pages (from-to) | 566-575 |
| Number of pages | 10 |
| Journal | Cement and Concrete Composites |
| Volume | 30 |
| Issue number | 7 |
| DOIs | |
| Publication status | Published - Aug 2008 |
Funding
The authors would like to recognize the National Science Foundation (NSF Grant 10143-23750-44) for their support of this research. The first author would like to recognize the Istanbul Technical University for their financial support during his stay in UC Berkeley. The authors would also like to thank Professor John A. Clements and Professor Jon Goerke of UC San Francisco for their assistance and discussions on surfactants, and Gordon Vrololjak of the Electron Microscope Laboratory (EML) for his assistance with the ESEM.
| Funders | Funder number |
|---|---|
| National Science Foundation | 10143-23750-44 |
| Istanbul Teknik Üniversitesi |
Keywords
- Air shell
- Anionic surfactant
- Cement paste
- ESEM
- Entrained air
- Foam index
- Microstructure
- Surface tension