High tensile strength fly ash based geopolymer composite using copper coated micro steel fiber

[Display omitted] •Incorporation of MSF controls the shrinkage of fly ash based geopolymer composite and minimizes it at 2% fiber content.•The MSF geopolymer composites shows a significant improvement in flexural strength and energy absorption.•Addition of MSF into geopolymer did not have an adverse effect on the compressive strength of the composite. As a ceramic-like material, geopolymers show a high quasi-brittle behavior and relatively low fracture energy. To overcome this, the addition of fibers to a brittle matrix is a well-known method to improve the flexural strength. Moreover, the success of the reinforcements is dependent on the fiber-matrix interaction. In this present study, effects of micro steel fibers (MSF) incorporation on mechanical properties of fly ash based geopolymer was investigated at different volume ratio of matrix. Various properties of the composite were compared in terms of fresh state by flow measurement and hardened state by variation of shrinkage over time to assess performance of the composites subjected to flexural and compressive load. The fiber-matrix interface, fiber surface and toughening mechanisms were assessed using field emission scan electron microscopy (FESEM) and atomic force microscopy (AFM) through a period of 56days. Test results confirmed that MSF additions could significantly improve both ultimate flexural capacity and ductility of fly ash based geopolymer, especially at early ages without an adverse effect on ultimate compressive strength.