What are the effects of calcium hydroxide on concrete

　　Calcium hydroxide also plays a big role in our common construction. Adding it to cement concrete can effectively improve the performance of all aspects. It has many positive effects on concrete when used well. So, what are the specific effects of calcium hydroxide on concrete?

　　 1. Calcium hydroxide can improve the long-term stability of concrete

Part of the alkaline environment in the cement stone pore solution comes from the hydroxides of alkali metals (such as K, Na, etc.) in the pore solution, but more comes from the presence of calcium hydroxide, Ca2+ and OH- in the pore solution. It ensures the continuous formation and stable existence of various hydration products, and provides the necessary media conditions for their mutual transformation. For example, when the concentration of lime in the solution is high, the hydration products mainly exist in the form of type I CSH gel. When the concentration of lime in the solution becomes lower, the type I CSH gel will be converted into type II CSH gel, etc. It can be seen that the presence of calcium hydroxide solution and calcium hydroxide crystals in cement stone is the basis for cement concrete to have certain mechanical strength and durability.

　　 2. Calcium hydroxide can increase the adhesion of concrete

The fineness of calcium hydroxide has a certain influence on the working performance of concrete, and the slump increases as the fineness of the mixed stone powder decreases. This situation can be analyzed from two aspects. The activity of calcium hydroxide is compared with cement. Clinker is much weaker. After calcium hydroxide partially replaces the cement, the initial cement clinker involved in hydration decreases, the water-binder ratio increases, the slump increases, and the smaller fineness stone powder calcium hydroxide has a greater filling effect. Well, the free water content of the system is relatively more, which can effectively increase the adhesion performance of concrete.

　　3. Calcium hydroxide gives concrete reinforcement

　　 The reinforcement of concrete is the prerequisite for the wide application of reinforced concrete. The passivation film can inhibit the anode reaction, thereby preventing the corrosion of the steel bar from occurring. The reason why the pH value of the liquid phase of concrete pores can reach 13. is because there is a large amount of calcium hydroxide alkaline solution in the liquid phase. When concrete is exposed to the atmosphere, carbon dioxide and water in the air can penetrate into the concrete along the capillary channels, and dissolve in the liquid phase of the capillary pores, and hydrate with calcium hydroxide, hydrated calcium silicate, etc. The product interacts to form calcium carbonate. Because the calcium carbonate formed by the reaction is an insoluble calcium salt, its volume is about 17% larger than the volume of the original reactant, which can block part of the capillary pores, which improves the chemical resistance of concrete. And impermeability properties are beneficial. The presence of calcium hydroxide is an important foundation for concrete to have reinforcement properties.