Effect of high wollastonite fiber incorporation on metakaolin base geopolymers' properties and microstructure

In order to study the effect of high addition of wollastonite fiber on the mechanical properties and cracking characteristics of metakaolin/slag geopolymer, wollastonite-metakaolin-slag geopolymer was prepared with the substitution mass fraction of wollastonite fiber (up to 40wt%) as the experimental parameter. The properties related to the content of wollastonite (mechanical strength, porosity and crack) were evaluated, and the effect of wollastonite fiber on the microstructure of geopolymer was studied. The results show that the addition of wollastonite fiber has a positive effect on inhibiting the cracking behavior of the geopolymer in dry environment, and it is continuously improved when the substitution amount is less than 40wt%. At the same time, it is also observed that the addition of wollastonite fiber has a positive effect on the mechanical properties of the geopolymer. The 28 days strength of the geopolymer with the substitution amount of wollastonite fiber of 20wt% reaches 70.2 MPa, which is 36% higher than the original compressive strength of metakaolin-based geopolymer. However, the continuous increase of wollastonite fiber will lead to the decrease of the compressive strength of the geopolymer. In addition, zeolite was detected in the composite, and the addition of wollastonite was beneficial to the development of zeolite phase.