Shrinkage Behavior of Composite Geopolymer Mortar Cured at Different Relative Humidities

Abstract:

In this study, the slag and metakaolin which contain rich elements of silica and aluminium were used to manufacture three types of composite geopolymer mortar: Type A (100% slag), Type B(70% slagand 30% metakaolin) and Type C(30% slag and70% metakaolin). Both the sodium hydroxide and sodium silicate solution were used as the activators. Experimental parameters included three ratios of SiO₂/Na₂O of 0.6, 0.7 and 0.8, three concentrations of alkali activator (7, 9 and 15%) and three water-to-solid ratios (0.33, 0.45 and 0.55), and four volumetric ratios of fine aggregate to whole mortar of 0, 10, 30, 50%, respectively. Two curing conditions of 50% relative humidity (RH), 25±2°C and 75% RH, 25±2°C were used for the dry shrinkage test. The results of study show that, at age of 28 days, the Type Bgeopolymer had the lowest drying shrinkage in the range between 450 and 760microstrains at 50%RH, and decreased to values between 270 and 340microstrainsat 70% RH.The average compressive strength of 89.3 MPa at age of 28 days for geopolymer mortar without metakaolin decreases to 74.7 MPa and 49.6 MPafor those with added metakaolin by 30 wt% to 70 wt%, respectively.

• Periodical: Advanced Materials Research (Volume 1064)
• Pages: 95-100
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.1064.95
• Online since: December 2014
• Authors: Ta Peng Chang, Zih Cian Chen, Tzong Ruey Yang
• Keywords: Dry Shrinkage, Geopolymer, Metakaolin, Relative Humidity, Slag

References

[1] J. Davidovits, J., Geopolymers: Inorganic Polymeric New Materials, Journal of Thermal Analysis, 37, 1633–1656 (1991).

DOI: 10.1007/bf01912193

[2] E. NajafiKani and A. Allahverdi, Investing shrinkage changes of natural pozzolan based geopolymer cement paste, Iranian Journal of Materials Science &Engineering, Vol. 8, No. 3, pp.50-60. (2011).

[3] N.K. Lee, J.G. Jang and H.K. Lee, Shrinkage characteristics of alkali-activated fly ash/slag paste and mortar at early ages, Cement & Concrete Composites 53, p.239–248(2014).

DOI: 10.1016/j.cemconcomp.2014.07.007

[4] X. -H. Yuan, W. Chen, Z. -A. Lu and H. Chen, Shrinkage compensation of alkali-activated slag concrete and microstructural analysis, Construction and Building Materials, 66, p.422–428 (2014).

DOI: 10.1016/j.conbuildmat.2014.05.085

[5] A. A. M. Neto, M. A. Cincotto and W. Repette, Drying and autogenous shrinkage of pastes and mortars with activated slag cement, Cement and Concrete Research, Vol. 38, 4, pp.565-574 (2008).

DOI: 10.1016/j.cemconres.2007.11.002

[6] S. A. Bernal, E. D. Rodrı´guez, R. Mejı´a de Gutie´rrez, M. Gordillo and J. L. Provis, Mechanical and thermal characterisation of geopolymers based on silicate-activated metakaolin/slag blends, Journal of Materials Science, Vol. 46, No. 16, pp.5477-5486 (2011).

DOI: 10.1007/s10853-011-5490-z