Fig. 11. Corrosion resistance of polyvinyl alcohol fibers (a) erosion by Cl-;(b) erosion by SO42-; (c) coordination of polyvinyl alcohol fiber and Nano-sio2[18]
Reproduced from [18], with permission from [Publisher]
The mixture of mineral particles and fibers can effectively improve the resistance of geopolymers to chemical erosion. Wang et al.[18] proved that geopolymer mortars with a polyvinyl alcohol fiber content of 0.6 ~ 0.8 v% and a nano-sio2 content of 1.0 ~ 2.0wt % present better chemical resistance, as shown in Fig. 11. The incorporation of nano-sio2 and polyvinyl alcohol fiber has a synergistic effect on the durability of geopolymer mortar. The bridging effect of polyvinyl alcohol fibers limits the crack propagation, and nano-sio2 is found conducive to filling the micropores and improving the microstructure. The addition of wollastonite, tremolite and basalt fibers to metakaolin base polymers can also improve sulfate and chloride ion erosion. The mixture with a ratio of 5% wollastonite, 5% tremolite and 2% basalt fiber sample possesses the highest compressive strength and the strongest erosion resistance[72]. If the polymer is prepared using 0.2% polypropylene fiber and 3% nanoparticles, the durability of the polymer can be increased by 67%[73]. The addition of basalt fiber to geopolymer can reduce weight loss after acid erosion and maintain the compressive strength as much as possible, which indicates the good durability of basalt fiber reinforced geopolymer[74]. The combination of cellulose fiber and fly ash can improve the durability of composite materials under the sulfate dry-wet cycle. In the late cycle, the pore volume increases obviously, the proportion of small holes decreases, and the mesopores increase. In this case, the durability of concrete can be consequently improved by optimizing the ratio to increase the proportion of harmless holes such as micro holes and small holes[75].