The waterproofing agent is an admixture formulated from chemical raw materials that can improve cement concrete and mortar’s water impermeability. When the waterproofing agent is used, it is usually mixed into cement concrete or cement mortar proportionally (sometimes painted on the surface and penetrates the cement concrete or cement mortar) to form waterproof concrete or waterproof mortar, thereby playing a waterproof role.

After the concrete is hardened, there are usually capillaries and gaps inside it so that water will pass through it; that is, concrete has permeability. If you use a waterproofing agent, you can significantly reduce this gap and improve the compactness of the concrete, thereby improving its density. Improve the impermeability of concrete.

Waterproofing agent is a type of waterproofing agent with waterproofing as its primary function. Although other admixtures, such as air-entraining and expanding agents, can also improve the impermeability of concrete, their respective waterproofing mechanisms are different, and they also have main functions: air entrainment and expansion, so they belong to different categories.

(1) Classification, waterproofing mechanism, and performance of waterproofing agents

1. Classification of waterproofing agents and waterproofing mechanism

The form of the waterproofing agents can be divided into liquid and solid waterproofing agents. According to the chemical composition of waterproofing agents, they can be divided into three categories: inorganic, organic, and composite systems. Inorganic waterproofing agents mainly include chloride metal salt waterproofing agents, inorganic aluminum salt waterproofing agents, sodium silicate waterproofing agents, concrete sealants, and silicate powders; organic waterproofing agents are also called polymer waterproofing agents, mainly in the form of compounds, generally refer to redispersible polymer powder, resin-emulsion, or water-soluble polymers, such as silicone waterproofing agents, cationic chloroprene latex, styrene-butadiene latex, organic matter waterproofing agents and metal soap waterproofing agents, fatty acid series, paraffin and asphalt emulsion and other varieties. A composite system refers to a type of waterproofing agent composed of inorganic mixtures, organic matter mixtures, or mixtures of inorganic matter and organic matter.

According to the waterproofing mechanism of waterproofing machines, waterproofing agents can be divided into two categories: permeability-reducing waterproofing agents and hydrophobic waterproofing agents.

A permeability-reducing waterproofing agent is a type of waterproofing agent that reduces the voids in concrete and improves the density of the material to achieve the purpose of impermeability. This type of waterproofing agent accounts for most waterproofing agents, mostly inorganic compounds. They or the compounds formed by their reaction with the products generated during cement’s hydration process can fill the concrete’s capillary channels and reduce the voids, such as iron oxide. A waterproofing agent generates calcium chloroaluminate, ferric hydroxide, and aluminum hydroxide colloids during the hydration process of cement to fill the gaps in the concrete and improve its compactness. Another example is silicate powder waterproofing agents. On the one hand, they are very fine and can fill gaps; on the other hand, because they have a particular activity, they can react with calcium hydroxide formed during the hydration process of cement to form colloidal hydrated silicon. Acid fills the gaps to improve water resistance.

Hydrophobic waterproofing agents differ from the previous types, characterized by sealing treatment. This type of waterproofing agent is primarily an organic substance characterized by hydrophobic treatment. They can change the capillary wall in concrete from hydrophilic to hydrophilic. To be hydrophobic, the surface of concrete becomes a hydrophobic surface, thereby reducing water seepage caused by capillary action and improving the water resistance of concrete. Silicone waterproofing agent represents this type of waterproofing agent.

The waterproofing mechanism of waterproofing agents to improve the water tightness of concrete and mortar can be divided into the following aspects:

a. Promote the hydration reaction of cement, generate hydration gel, and fill early gaps;

b. Add fine substances to fill the gaps in the concrete and block water seepage channels;

c. Incorporate hydrophobic substances or react with ingredients in cement to form hydrophobic ingredients;

d. Form a dense film in the gaps of concrete (mortar);

e. Coating or penetrating soluble components and combining with the soluble components produced during the cement hydration reaction to form insoluble crystals.