Sulphoaluminate cement is a new type of cement composed of anhydrous sulphur (iron) calcium aluminate and dicalcium silicate as the main minerals. The sulphoaluminate cement series are used alone or in conjunction with ZB type sulphoaluminate cement special admixtures, and are widely used in emergency repairs and construction projects, prefabricated components, GRC products, low-temperature construction projects, seawater corrosion resistance projects, etc.
Sulphoaluminate cement raw materials: aluminum raw materials (mainly provide Al2O3, but also provide SiO2 and Fe2O3) lime raw materials (mainly provide CaO) sulfur-based raw materials (mainly provide SO3) fuel: bituminous coal. Raw material and fuel requirements: Bauxite: Al2O3>60%, SiO2<15% Limestone: CaO>50%, SiO2<3.5%. Dihydrate gypsum: SO3>38%. Anhydrite: SO3>38% industrial bituminous coal: calorific value>23826kJ/kg, ash content<3.5%, volatile content>25%. Total harmful ingredients of raw materials: R2O<0.5.
1. The relative density of sulphoaluminate cement clinker is lower than that of Portland cement clinker, and generally fluctuates between 2.87 and 2.92.
2. The hydration products of sulfoaluminate cement are mainly composed of ettringite, aluminum glue and iron glue.
3. The initial setting time of sulphoaluminate cement is much faster than Portland cement, generally fluctuates between 30 and 50 minutes, and the final setting fluctuates between 40 and 90 minutes.
4. The total heat of hydration of sulfoaluminate cement is not higher than the total heat of hydration of Portland cement, about 45 to 50 kJ/g, but it is released in 8 to 48 hours.
5. The pore structure of sulfoaluminate cement is significantly different from that of Portland cement: the total porosity is low <15%; the average pore size is small, and most of the pore size is less than 30nm. The most acceptable pore size (1:1 mortar) is less than 2.5nm, and pores around 1.8nm account for a large proportion; the shape of the holes is mostly ink bottle holes. Such a pore structure is the key to the formation of the excellent properties of sulfoaluminate cement such as impermeability, frost resistance, corrosion resistance, and dry shrinkage.
6. Compared with Portland cement, sulphoaluminate cement has low alkalinity in the hydration liquid phase. Therefore, the alkali-aggregate reaction that may occur due to the use of alkali-active aggregate can be suppressed.
Sulphoaluminate cement is characterized by fast setting, high strength, high frost resistance, corrosion resistance, high impermeability, expansion performance, and low alkalinity. At present, it is mainly used in: winter construction projects, emergency repair and construction projects, preparation of sprayed concrete, production of cement products and concrete prefabricated components, preparation of shrinkage-compensating concrete and impermeability projects, production of fiber-reinforced cement products, etc. Sulphoaluminate cement is a new series of varieties in the history of the world's cement development. It is still in the application and promotion period. However, it has shown very optimistic development prospects.
