The Highly Effective Technology To Active Steel Slag And Its Application In Green Construct Materials

Steel slag is the byproducts from the iron and steel manufacturing process, which is widespread all over the world. It can pollute the environment and affect the sustainable development of the iron and steel industry and bring the huge pressure and burden to national economic sustainable development. Along with implementation of national related policy, the cycle using of the steel slag will become an important measurement for energy conversation and environment protection. Since the steel slag has similar mineral constituent with the cement clinker, it has a great important meaning for researching and application as a mineral additive in the field of cement.In this paper, the steel slag provided by Hunan Lianyuan Iron & Steel Group is used as the raw material in the experiments. Mechanical grinding and different chemical activators are applied on activate the steel slag. And the ultra fine particles of Beta-dicalcium silicate (β-C₂S) have been successfully synthesized via decomposition-reorganization method. This main work and achievements will be introduced in the following paragraphs.Composition and the structure feature of steel slag powders are investigated systematically. The effect of mechanical grinding on the size distribution, the Blaine specific surface value and phase-transition is also discussed in the thesis. Several factors such as different ball, different milling time and so on have great effect on the size distribution and Blaine specific surface value. Results show that C ball, the mass ratio of ball to raw materials(5/1) and 5h is the optimum condition for mechanical grinding. Under the optimum condition for mechanical grinding, the Blaine specific surface value is 5846 cm²/g and the percentage of fine size powders passing through standard sieve (0.09 mm) is the most.The activators such as CaSO₄, Na₂SO₄ and liquid Na₂SiO₄ added in steel slag which can damage the surface structure of steel slag is to active the powders for improving the hydration property. That the expanded intensity of Si-0 stretching band appearing at 972 cm^-1 and a weak Si-O bending band at about 459 cm^-1 proves that the activators play a significant role in activating steel slag. It has been found that the type of activators and its dosage have a very important effect on hydration process. The mechanism of that the maximum of compressive strength shifts from high dosage of CaSO₄ or liquid Na₂SiO₄ to the low dosage with different hydration time is studied in the series of experiments.Thermodynamic data of the relationship between the temperature and -ΔG_R⁰(kJ/mol) in CaO-SiO₂ system and others are calculated to get the optimum conditions to prepareβ-C₂S. Different thermal treatments are also considered in this thesis.The ultra fine steel slag powders are applied in cement and concrete industry. As a mineral additive in the concrete, it can replace 30% cement (grade 32.5) for preparing C30 concrete. The steel slag-silicate cement (grade 42.5) can be obtained when 5%-15% clinker is replaced by ultra fine steel slag. If ultra fine steel slag and blast furnace slag simultaneously used as additive to replace clinker, the steel slag-silicate cement (grade 32.5) can be obtained when 20%-30% clinker is replaced by ultra fine steel slag, which propeties can meet the national standard of GB13590-2006.