Characterization and compressive strength of fly ash based-geopolymer paste Ari Widayanti, Ria Asih Aryani Soemitro, Hitapriya Suprayitno and Januarti Jaya Ekaputri MATEC Web Conf., 195 (2018) 01023 Published online: 22 August 2018 DOI: 10.1051/matecconf/201819501023