Mathematical model for predicting stress-strain behavior of low calcium fly-ash based geopolymer concreteNutakki Sai Ketana, V Srinivasa Reddy, M V Seshagiri Rao and S ShrihariE3S Web Conf., 309 (2021) 01103DOI: https://doi.org/10.1051/e3sconf/202130901103