To explore the possibility of using solid waste instead of cement as the cementitious material for bases, the 28 d compressive tests on the mortar specimens with different mix proportions of three admixtures (slag powder (SP), fly ash (FA), and desulfurization gypsum (FDG)) and four admixtures (SP,FA,FDG, and steel slag powder) were conducted, and the mechanism of each component in the hydration reaction in three admixture and four admixture cementitious material were analyzed. Then an 28 d compressive strength R28 prediction model was proposed, and based on the optimal mix proportion, sand specimens and slurry specimens were made and tested. The results show that the significant effects of single factor in three admixture system is ranked as FA>SP, there is an interaction between FA and SP, and the optimal mix proportion is w(SP）∶w(FA）∶w(FGD）=35∶5∶10[BFQB]; The significant effects of single factor in four admixture system is ranked as SP>SS>FA, the order of significant interaction is(SP+FA)>(FA+SS)>(SP+SS), and the optimal mix proportion is w(SP）∶w(FA）∶w(SS）∶w(FGD）=438∶241∶225∶96[BFQB]. The R28 of mortar specimens made of three admixtures according to the optimal mix proportion do not meet the specification requirements. All indicators of specimens in four admixture meet the specification requirements, and are superior to P·S·A 325 grade cement. The four admixture cementitious materials can replace cement for bases.