Workability and Strength Properties of Class C Fly Ash-Based Geopolymer Mortar Remigildus Cornelis, Henricus Priyosulistyo, Iman Satyarno and Rochmadi MATEC Web Conf., 258 (2019) 01009 Published online: 25 January 2019 DOI: 10.1051/matecconf/201925801009