TY JOUR TI EFFECT OF VARIATIONS IN VITREOUS PHASE OF LOW-CALCIUM ALUMINOSILICATES ON STRENGTH PROPERTIES OF GEOPOLYMER SYSTEMS KW low-calcium aluminosilicates KW geopolymerization KW degree of SiO2-connectivity JO Bulletin of Belgorod State Technological University named after. V. G. Shukhov AU Kozhuhova, N.I. AU Zhernovskiy, I.V. AU Sobolev, K.G. PY 2018 IS 3 PB Belgorod State Technological University named after V.G. Shukhov