Experimental Research on New Sustainable Geopolymer Mortars Reinforced and Not Reinforced with Natural Fibers

The paper describes experimental research voted to verify the mechanical characteristics of very sustainable geopolymer mortars and to try to improve their mechanical characteristic using natural fibers. Particularly, there were used and tested geopolymer mortars using a geopolymer matrix obtained from very cheap and sustainable fly ashes (as they come from the waste recycling). About the natural fibers, they were used hemp short fibers as they are very durable and sustainable. It was designed and performed a bending test program for twelve reference samples of geopolymer mortar beams (without fibers) divided into two group of six samples with different proportions between fly ashes and sand. Then, it was designed and performed the bending test program for the geopolymer mortars with the addition of hemp short fibers: twelve samples with a lower percentage of fiber and twelve samples with a higher percentage of fibers. Each group of twelve samples was divided into two group of six samples with different proportions between fly ashes and sand. Then it was designed and performed a compression test program: there were used the same beams, after their cracking in the bending tests, to obtain cubic samples (after a regularization of the faces). Thus, there were twenty-four reference cubic samples without fibers and forty-eight cubic samples with fibers for the compression tests.