Characteristics of cement pastes containing sulphoaluminate and belite prepared from nano-materials

The sulphoaluminate phase C(4)A(3)(S) over bar as well as beta-C2S represent an important factor for the preparation of rapid hardened sulphoaluminate-belite cement. The hydration of C(4)A(3)(S) over bar forms ettringite and monosulphate hydrates in addition to the liberation of aluminium hydroxide. The hydration rate of belite is much slower than that of C(4)A(3)(S) over bar, but becomes significant at later ages. Two mixes containing sulphoaluminate (C(4)A(3)(S) over bar) and monosulphate mix (C(4)A(3)(S) over bar, with 8C (S) over bar + 6C) in addition to belite (beta-C2S) were synthesized from nano-materials after firing at 1250 degrees C. The hydration characteristics of 10\% C(4)A(3)(S) over bar or 10\% C(4)A (S) over bar in addition to 10\% beta-C2S on the expanse of OPC were studied. The results revealed that the substitution of OPC with sulphoaluminate mixes as well as belite shortens the setting times. The rate of hydration of OPC with sulphoaluminate-belite phases is increased from the formation of more sulphoaluminate hydrates and the consumption of protlandite. Also, these mixes give higher chemically combined water contents. The monosulphate hydrate is deposited in some of open pores in the dormant period of hydration that tends to increase the compressive strength of sulphoaluminate-belite cement pastes. (C) 2012 Elsevier Ltd. All rights reserved.