| INORGANIC MATERIALS AND CERAMIC MATRIX COMPOSITES |
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| Pore Structure and Compressive Strength of Fly Ash-Metakaolin Based Geopolymer |
| WANG Shunfeng1, MA Xue1, ZHANG Zuhua2, WANG Aiguo3, LI Yalin4
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1 College of Material Science and Engineering, Southwest University of Science and Technology, Mianyang 621010;
2 College of Civil Engineering, Hunan University, Changsha 410012;
3 Anhui Key Laboratory of Advance Building Materials, Anhui University of Architecture, Hefei 230022;
4 Sichuan Tianfu Fire Material Co., Ltd., Chengdu 610031 |
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Abstract The great advantages of geopolymers, such as excellent mechanical property, chemical stability, high temperature resistance properties and so on, have been attracted much attention in recent years. They are gradually deemed to be potentially revolutionary materials in the field of building, fire resistance and stabilization radioactive and toxic wastes. This study was aimed to investigate the structure and compressive strength of geopolymer with high content of metakaolin and the metakaolin dosage affecting them. The pore structure (including pore diameter distribution and porosity), reaction products structure and fracture behavior of geopolymers, were characterized respectively by MIP, FT-IR and SEM. The pore diameter distribution was influenced obviously by the water to binder mass ratio, the diameter of the most probable pore was dispersedly distributed in the region of several nm to one hundred nm. As water/binder ratio was constant and metakaolin dosage increases from 25%(mass fraction) to 60%(mass fraction), abundant gel pores were detected in all samples, whereas the diameter of the most probable pore was diminished from 40 nm to 26 nm. In addition, although the total porosity was not much different, the porosity of harmful pore decreased from 3.6% to 0.09%. An increase in the metakaolin content promoted the number of [AlO4] in a ring of aluminasilicate gel, which resulted in the structure more denser and more homogenous, especially improved the interface bonding performance between unreacted fly ash particles and the gels. The substitution of 60% fly ash by metakaolin, the crack propagation around the pore or weak interface of fly ash particles was effectively controlled, thus significantly improving the compressive strength and at 75.5 MPa after 7 d curing.
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Published: 18 September 2018
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2018, Vol. 32 
