TY JOUR TI EXPRESS-METHOD FOR DETERMINATION OF COMPRESSIVE STRENGTH OF GEOPOLYMER BASED ON LOW-CALCIUM FLY ASH KW low-calcium fly ash KW reactivity estimation KW calculated express-method KW compressive strength of geopolymer paste JO Bulletin of Belgorod State Technological University named after. V. G. Shukhov AU Shehovcova, Y.A. AU Zhernovskiy, I.V. AU Kozhuhova, N.I. AU Kovtun, M.N. AU Kersli, E.. AU Zhernovskaya, I.V. PY 2018 IS 3 PB Belgorod State Technological University named after V.G. Shukhov