In this paper, the effects of waste glass powder on reaction kinetics, gel characteristics, as well as workability and mechanical property of two typical binding systems: Portland cement system and alkali activation system, are investigated. The commercial silica fume was used as a comparative supplementary cementitious material. The results show that waste glass incorporation improves the workability, while silica fume presents an obvious negative effect. Both waste glass powder and silica fume delay the early age reaction to some degree, but the reduction is less significant for waste glass. The addition of waste glass shows limited effect on the typical gel structure in Portland cement system; while in alkali activated system, silica fume incorporation results in more polymerized Si–O structure than waste glass. Thermal analysis indicates that waste glass powder exhibits relatively lower reactivity than silica fume in Portland cement system, but very similar reactivity in alkali activated system. Mixes containing waste glass show comparable but slightly lower compressive strength than the ones with silica fume addition, but a better balance between performance and cost is achieved. The microstructure characterizations further confirm the beneficial effect of waste glass powder in producing cementitious binding materials.