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Advanced Construction Materials and Technologies
MPa, but higher substitutions imply a decrease in mechanical strength: a 50 wt % substitution generates a value of 14.47 MPa, which means a fall of 17.5%.
The mechanical strength of these materials is closely related to the porosity generated during their aged and the amount of geopolymeric gel formed. It is observed that as the olive grow fly ash increases its percentage by weight more dense and, therefore, more compact materials are formed.
The replacement of olive grove fly ash by metakaolin generates a significant decrease in apparent porosity, 39.08% for pure MK geopolymers compared to 9.86% for a 25% OGFA wt% substitution, which represents a reduction of 74.77%, and 85.59% for geopolymers with 75% OGFA wt%. This reduction in porosity is also reflected in the reduction of water absorption: - 79.32% and in the increase of bulk density values, + 22% OGFA wt%. Subsequent increases of ash added causes the values of water absorption to decrease even more, so for a substitution of 75%, water absorption decreases by 88.31%, while the bulk density remains constant.
It can be established that up to 25 wt % of olive grove fly ash substitution by metakaolin generates denser materials, with less water absorption as a consequence of a lower porosity and, therefore, generates better mechanical benefits.
4. Acknowledgment
This work has been funded by the project Development and characterization of new geopolitical composites based on waste from the olive industry. Towards a sustainable construction (MAT2017-88097-R), FEDER/Ministry of Science, Innovation and Universities, State Research Agency.
5. References
Rakhimova N.R., Rakhimov, R.Z. (2019), Toward clean cement technologies: A review on alkali-activated fly-ash cements incorporated with supplementary materials. J Non-Cryst Solids. 509, pp 31-41.
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