Film-forming curing agent refers to a product that can form an impermeable film on the concrete surface after application, so as to avoid evaporation of water from the concrete surface and keep the concrete moist. Model curing agent can effectively reduce the plastic shrinkage and cracking degree of concrete, and it has obvious technical and economic advantages for concrete curing in arid and windy sand areas.
(1) water glass curing agent:
Sodium silicate (nNa2O? SiO2) or potassium silicate (nK2O? SiO2) is the main component and is a transparent viscous liquid. Sodium silicate curing agent is cheap, and it can react with calcium hydroxide (surface 1mm~3mm) produced by cement hydration after spraying on the concrete surface, forming colloidal silicate to fill the pores on the concrete surface, making the concrete surface dense, preventing the evaporation of water inside the concrete, and playing a role in moisturizing the concrete. The disadvantage of sodium silicate curing agent is that it is difficult to form a waterproof film with ideal integrity. Some data show that when this curing agent is used in the arid area of 30℃, the concrete surface is prone to fish-net cracking or looseness.
(2) Polymer film-forming curing agent:
Polymer film-forming curing agent is a widely used water-retaining curing agent, including emulsion and solution. After concrete is poured and molded, it is smeared on the surface of concrete, and polymer particles gather to form a waterproof film, which not only has a good moisturizing and curing effect, but also can effectively prevent capillary channels formed when water evaporates, thus improving the strength of concrete. Emulsion curing agents mainly include paraffin emulsion and asphalt emulsion, which have some problems such as unstable performance, easy to leave traces and poor curing effect. The solutions are neoprene, acrylic resin, vinyl resin and ethylene peroxide, which will pollute the environment.
Introducing superhydrophobic monomer into the synthesis of polymer emulsion curing agent can effectively reduce the hydrophilicity of the membrane, thus reducing the dissolution and diffusion speed of water molecules in the membrane and greatly improving the curing effect.
(3) Polymer water-absorbent resin curing agent:
Polymer water-absorbent resin is a new type of polymer material, which can absorb water several times or even hundreds times heavier than itself. Once swollen to form hydrogel, it is difficult to separate water even under pressure, and its water retention is excellent. On the one hand, it is difficult for polymer water-absorbent resin curing agent to evaporate water into air, on the other hand, it transfers water into concrete according to capillary principle. Therefore, as long as water is poured once and fixed on the surface of water-absorbent resin, solidified water can be provided through slow and uninterrupted release.
From this point of view, different from the water-retaining function of polymer emulsion curing agent, polymer water-absorbent resin has the function of water absorption and curing. Water-absorbent resin curing agent is mainly suitable for desert and other areas with large temperature difference between day and night, so as to keep concrete in high humidity environment.
(4) Inorganic and polymer composite curing agent:
This kind of curing agent makes full use of the permeability of inorganic substances and the water retention of organic polymers, and has become a hot spot in research and application in recent years.
Osmotic curing agent, also known as film-free curing agent, is mainly composed of polyhydroxy aliphatic hydrocarbon derivatives. Although this curing agent can't form a film after spraying on the concrete surface, it can penetrate into the concrete because of its low surface tension, preventing the evaporation and loss of water inside. The main feature of osmotic curing agent is that it does not react chemically with concrete surface and does not affect the later decoration and protection of concrete.