The alkaline-slag cement (ASC) cementing material has been widely used in engineering projects in many countries. It has excellent performance in terms of corrosion resistance and durability, low heat of hydration, and also has the advantages of high adaptability and construction process. However, the main disadvantage is that the strength and water resistance of ASC are weaker than ordinary Portland cement (OPC). In order to overcome this defect and improve the performance of ASC, many researchers have conducted research and obtained some encouraging results.
The alkaline-slag cement (ASC) cementing material is prepared by mixing slag and alkaline materials, such as fly ash and lime, with a certain amount of Portland cement clinker and gypsum, and then heat treating and grinding the cement paste. In terms of alkaline materials, fly ash has better reactivity than other alkaline materials, and therefore has become a commonly used material for the preparation of ASC. In terms of slag, slag from steel plants is the most commonly used material, which contains more alkaline substances, and thus has better reactivity, which increases the strength and water resistance of ASC significantly.
In the preparation process of ASC, there are two decisive factors, namely, the amount and type of alkaline material and slag, and the heat treatment process. Studies have shown that when the amount of alkaline material and slag is greater than 15% and 4.5%, respectively, the strength and water resistance of ASC will be significantly improved. The heat treatment process mainly includes acid decomposition and ph value adjustment. With regard to the preparation of ASC, acid decomposition can be used to reduce the hydration energy of ASC by decomposing the hydrophobic surface of the slag particles, and thus reduce the degree of hydration retrogressive development. At the same time, the ph value adjustment can also be used to suppress the leaching of certain components at low temperatures.
The strength and water resistance of ASC can also be improved by adding some mineral admixtures, such as silica fume, metakaolin and iron powder, which can promote micro-crystalline growth and reduce the hydration retrogressive development of ASC. In addition, some pozzolanic material and high fineness cement can also be added to improve the performance of ASC cement.
In conclusion, the alkaline-slag cement has become an important cementing material due to its excellent corrosion resistance and durability, low heat of hydration, and high adaptability and convenience. However, its strength and water resistance are weaker than ordinary Portland cement. To improve its performance, some measures should be taken such as the selection of proper alkaline materials and slags, the optimization of heat treatment process, and the addition of mineral admixtures. With these measures taken, the strength and water resistance of ASC can be enhanced, thus improving its engineering performance.
