Experimental investigation on the durability of geopolymer repaired mortar based on metakaolin and blast furnace slag
Metakaolin (MK) and blast furnace slag (GGBS) are commonly used solid raw materials for the preparation of geopolymers. Geopolymers prepared by the combination of the two have the advantages of room temperature curing,high bond strength,fast hardening,and early strength,and can be used as repair materials. However,the change of durability of repair materials caused by the change of the ratio of the two has not been fully understood. Therefore,this article set different GGBS/(MK+GGBS) values (mass ratio:0,20％,40％,60％,80％,and 100％),tested the water absorption of geopolymer repair mortar and contact angle,visually observed the degree of caustic penetration of geopolymer,and tested the changes in mechanical properties of geopolymer before and after caustic penetration to compare the resistance to caustic penetration of geopolymer. In this paper,geopolymer was immersed in 0.5M (mol/L) HCl solution for 1,3,and 5 days,and the acid resistance of geopolymer was evaluated by visual observation and testing of the mass and strength loss of geopolymer. Thermogravimetric (TG),Fourier infrared spectroscopy (FTIR),and X-ray diffraction (XRD) were used to discuss the acid-resistance mechanisms of high and low Ca systems. In addition,considering that the compatibility of the repair material with the matrix is also critical,the cement was used as a control variable in the dry shrinkage test,the bond specimens were used as the object in the acidification test,and the thermal deformation of the geopolymer and the cement was tested to assess the compatibility of the two. The results show that when the ratio of MK and GGBS is appropriate,the geopolymer has a denser structure,showing a lower water absorption and caustic penetration degree. When the content of MK is high,the geopolymer gel produced has a stronger acid resistance. Appropriate increase of GGBS can improve the durability of the repair material by improving the density of the structure. The research results can provide technical reference for the fast repair materials with high performance and durability for rigid pavement.
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