In this paper, preparation and mechanical properties of Alite-C(2.75)B(1.25)A(3) (S) over bar cement concrete was studied. The result showed the concrete had properties of higher early-age strength and more steady late-age strength than Portland cement concrete. In the experiment higher workability concrete was produced through experimental method. Compared with Portland cement concrete, the compressive strength of the concrete was investigated. The result showed that the compressive strength of the two concretes decreased with the increase of the water-cement ratio(W/C), but the compressive strength of Alite-C(2.75)B(1.25)A(3) (S) over bar cement concrete was much higher than that of Portland cement concrete, especially the early-age compressive strength. The compressive strength of Alite-C(2.75)B(1.25)A(3) S cement concrete at an early age of 24 hours could reach 22.81MPa for w/c=0.45, 17.29MPa for w/c=0.50 and 17.04MPa for w/c=0.55 respectively, and they were about 50 to 65 percent higher than those of Portland cement concrete. The compressive strength of 7 days could reach about 80 to 90 percent of 28-day strength in Alite-C(2.75)B(1.25)A(3) (S) over bar cement concrete. Although the mechanical properties of Alite-C(2.75)B(1.25)A(3) (S) over bar cement were lower than that of Portland cement after 28 days curing in the experiment, the compressive strength of the concrete was higher than that of Portland cement concrete.. The compressive strength of Alite-C(2.75)B(1.25)A(3) (S) over bar cement concrete at an age of 28 days could reach 55.85MPa for w/c=0.45, 48.01MPa for w/c=0.50 and 44.21MPa for w/c=0.55 respectively, and the compressive strength of Portland cement concrete reached 54.34MPa, 47.52MPa and 43.89MPa at the same water-cement ratio(W/C). The microstructure and the interface of cement-aggregate was investigated by Scanning Electron Microscope(SEM). The result showed that the interface of cement and aggregate was more close-grained of Alite-C(2.75)B(1.25)A(3) (S) over bar cement concrete than that of Portland cement concrete. Distributing of particulate bulk was more uniformity and a majority of clinker was wrapped by hydrated gel in Alite-C(2.75)B(1.25)A(3) (S) over bar concrete. The structure of Alite-C(2.75)B(1.25)A(3) (S) over bar cement concrete was much more compact than that of Portland cement concrete.
