Drying shrinkage of fly ash geopolymeric mortars reinforced with polymer hybrid fibres

Abstract

Drying shrinkage performance is a very important factor for reinforced concrete composites because a high shrinkage performance is associated with a high cracking tendency, which leads to future durability problems. Geopolymeric mortars show much higher drying shrinkage than Portland cement-based composites because they use a low amount of structural water and thus have a higher pore content than ordinary Portland cement composites. Therefore, the use of fibres is especially interesting to counteract the drying shrinkage tendency of geopolymeric mortars. This paper provides results on the restrained and unrestrained shrinkage performance of fly ash-based geopolymeric mortars reinforced with short polymer hybrid fibres (SPHF). The results show that SPHF reduces the shrinkage cracking tendency. A content of SPHF as low as 0·08% was able to reduce the average crack width by four times when compared with non-reinforced mortars. Increasing the content of SPHF from 0·08 to 0·8% reduces the time of appearance of the first crack by 25 h and reduces the average crack width by two times.