Durability performances of wollastonite, tremolite and basalt fiber-reinforced metakaolin geopolymer composites under sulfate and chloride attack

- A geopolymer was proposed based on metakaolin blended with mineral particles and fiber.
- The mineral particles and fiber play a reinforced role.
- The resistance to the sulfate and chloride attack was enhanced.
- MK blended with 5% WS, 5% TR and 2% SBF exhibits the optimal strength.

This paper aims to investigate the durability related performances of geopolymer composite materials that synthesized by alkali activation of metakaolin (MK) with reinforcement of wollastonite (WS), tremolite (TR) and short basalt fiber (SBF). The resulting geopolymer composites were exposed to sodium sulfate (Na2SO4) solutions (concentration 5-20%) and sodium chloride (NaCl) solution (concentration 5-20%). The compressive strengths, morphological evolution, microstructure and pore structure of the geopolymer composite specimens were examined to evaluate their durability performance. The result showed that the mix of a MK with addition of 5% WS, 5% TR, and 2% SBF exhibits the highest compressive strength in the studied range of mixture design. The compressive strength of geopolymer composites decreased with increasing of the concentration of Na2SO4 and NaCl solutions, and with the extension of exposure period as well. The average pores size of geopolymer shifted from 22 nm to 92 nm after the sulfate exposure, and the total porosity also increased. This is in agreement with the compressive strength development. The findings of this study suggest that reinforcement by mineral particles and fibers is an effective approach to increase the compressive strength of geopolymer; and it is also beneficial to the enhancement of the resistance to sulfate and chloride attack.