Due to the explosive growth of the world's population, the demand for resources in every country has increased. Among them, cement-based materials have become important materials to adapt to the urbanization process. Currently, cement-based materials account for more than one-third of the total amount of materials extracted from the earth each year, and the increase in cement production and use has led to an increase in carbon dioxide emissions in current technology.
Among them, the manufacturing industry of silicate cement is one of the main industries that cause global warming, and its carbon emissions account for 10% of the total human activity emissions. Pollutants generated during the production process of silicate cement include carbon dioxide, dust, nitrogen oxides, sulfur oxides, etc. In comparison, non-Portland cement not only has excellent mechanical performance and high corrosion resistance to media performance but also has environmental and economic applicability. Therefore, calcium aluminate cement is a substitute for traditional cement.
Calcium aluminate cement is a cement with one or two main mineral components of calcium aluminate. It is made by mixing natural bauxite or industrial alumina with calcium carbonate (limestone) in a certain proportion and then calcining or electric melting. It can also be made by melting iron bauxite and limestone. The coagulation and hardening speed of calcium aluminate cement are also related to the curing temperature. With the increase of the curing temperature, the CA2 mineral speeds up the coagulation and hardening speed, while the CA mineral is a little anomalous, faster at around 20 degrees Celsius and slower at 30 degrees Celsius, and faster again above 30 degrees Celsius. Choosing the appropriate curing conditions is crucial based on the phase change during the heating process of the aluminum sulfate hydrate. Because the hydrated products generated during the hydration of calcium aluminate cement vary with different curing conditions.
When used in practice, many different grades of calcium aluminate cement can be seen, and these grades represent the strength of the cement after a certain period of curing. For example, calcium aluminate cement with CA as the main mineral component is generally labeled with the strength reached after curing for 3 days. And, calcium aluminate cement with CA2 as the main mineral component is labeled with the strength reached after curing for 7 days. It should be noted that additives play an important role: hindering the formation of unnecessary metastable phases such as CA, CAH10, C2AH8, thereby forming stable hydration products C3AH6 and AH3 directly. In addition, additives shorten the induction period, thereby changing the heat flow curve, leading to the appearance of the thermal peak earlier.