Details
| Original language | English |
|---|---|
| Pages (from-to) | 2585-2590 |
| Number of pages | 6 |
| Journal | Journal of the American Ceramic Society |
| Volume | 93 |
| Issue number | 9 |
| Early online date | 15 Apr 2010 |
| Publication status | Published - Sept 2010 |
Abstract
Aluminosilicate gels were synthesized by mixing metakaolin with potassium water glass solution. Mechanical strength values showed a strong increase between 25 and 100 h but decreased again above 200 h for aging at 25°C. A similar curve was observed during aging at 50°C but the maximum strength shifted to shorter time. Aging at 90°and 130°C revealed only the decreasing wing in mechanical strength. The strengthening and weakening during aging at 25°C were further investigated by the molybdate method and infrared absorption spectroscopy. The results indicate basically that different time-dependent formations of two structural units dominate the mechanical properties: (i) A fast formation of longer (polymeric) silicate chains is enforced by the consumption of hydroxide in the solution of metakaolin up to about 25 h of aging. (ii) An aluminosilicate network grows slowly and encloses the chain-like units giving rise to an initial increase in strength within 100 h. During further aging the destruction of the polysilicate chains weakens the geopolymer. The destruction of the chain-like units is explained by the increasing amount of hydroxide produced during network condensation. The results imply that the same reactions occur for aging at a higher temperature but on faster time scales.
ASJC Scopus subject areas
- Materials Science(all)
- Ceramics and Composites
- Materials Science(all)
- Materials Chemistry
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In: Journal of the American Ceramic Society, Vol. 93, No. 9, 09.2010, p. 2585-2590.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Weakening of alkali-activated metakaolin during aging investigated by the molybdate method and infrared absorption spectroscopy
AU - Rüscher, Claus H.
AU - Mielcarek, Elzbieta
AU - Lutz, Wolfgang
AU - Ritzmann, Attila
AU - Kriven, Waltraud M.
PY - 2010/9
Y1 - 2010/9
N2 - Aluminosilicate gels were synthesized by mixing metakaolin with potassium water glass solution. Mechanical strength values showed a strong increase between 25 and 100 h but decreased again above 200 h for aging at 25°C. A similar curve was observed during aging at 50°C but the maximum strength shifted to shorter time. Aging at 90°and 130°C revealed only the decreasing wing in mechanical strength. The strengthening and weakening during aging at 25°C were further investigated by the molybdate method and infrared absorption spectroscopy. The results indicate basically that different time-dependent formations of two structural units dominate the mechanical properties: (i) A fast formation of longer (polymeric) silicate chains is enforced by the consumption of hydroxide in the solution of metakaolin up to about 25 h of aging. (ii) An aluminosilicate network grows slowly and encloses the chain-like units giving rise to an initial increase in strength within 100 h. During further aging the destruction of the polysilicate chains weakens the geopolymer. The destruction of the chain-like units is explained by the increasing amount of hydroxide produced during network condensation. The results imply that the same reactions occur for aging at a higher temperature but on faster time scales.
AB - Aluminosilicate gels were synthesized by mixing metakaolin with potassium water glass solution. Mechanical strength values showed a strong increase between 25 and 100 h but decreased again above 200 h for aging at 25°C. A similar curve was observed during aging at 50°C but the maximum strength shifted to shorter time. Aging at 90°and 130°C revealed only the decreasing wing in mechanical strength. The strengthening and weakening during aging at 25°C were further investigated by the molybdate method and infrared absorption spectroscopy. The results indicate basically that different time-dependent formations of two structural units dominate the mechanical properties: (i) A fast formation of longer (polymeric) silicate chains is enforced by the consumption of hydroxide in the solution of metakaolin up to about 25 h of aging. (ii) An aluminosilicate network grows slowly and encloses the chain-like units giving rise to an initial increase in strength within 100 h. During further aging the destruction of the polysilicate chains weakens the geopolymer. The destruction of the chain-like units is explained by the increasing amount of hydroxide produced during network condensation. The results imply that the same reactions occur for aging at a higher temperature but on faster time scales.
UR - http://www.scopus.com/inward/record.url?scp=77956370855&partnerID=8YFLogxK
U2 - 10.1111/j.1551-2916.2010.03773.x
DO - 10.1111/j.1551-2916.2010.03773.x
M3 - Article
AN - SCOPUS:77956370855
VL - 93
SP - 2585
EP - 2590
JO - Journal of the American Ceramic Society
JF - Journal of the American Ceramic Society
SN - 0002-7820
IS - 9
ER -