Concrete is the most widely used construction material in the world. Concrete mixed and cast according to standards has good strength, use function and durability. However, in actual use, concrete will be exposed to various conditions, which is prone to cracking problems. This is why almost all commercial concrete projects need to be waterproof.

The traditional concrete waterproofing practice is to spray waterproof paint on the surface or apply self-adhesive waterproofing membrane. In the past few decades, the waterproof technology has continuously developed, and a technology called concrete self-waterproof has appeared, which can make the concrete itself impervious to water. This concrete self-waterproof product can be used on the existing concrete surface, or it can be directly added to the concrete mixture to make it a component of concrete. Using concrete self-waterproof technology, not only the concrete can be better protected, but also the extra waterproof construction time and labor are saved after the concrete is poured.

1. Mechanism

Concrete self-waterproof products are sold by many companies, and the product formulas are also different. However, the working mechanism of concrete self-waterproof products is based on one of the following three types: as a compacting agent, filled in the micropores of the concrete matrix to make it impervious to water; as a water-repellent agent, making concrete hydrophobic; Water can form tiny water-blocking crystals, sealing micropores and hair-like cracks in concrete.

The compacting agent uses volcanic ash as a raw material, usually silicon powder or other silicates, which can be filled in the micropores of the concrete matrix. Silica fume is an industrial by-product, very small, about the size of cigarette dust particles. As a way to control pollution, these particles can be collected and concentrated as a concrete admixture. The density of silica in the compacting agent is relatively high, and it is easy to react with water. Filling the concrete micropores can increase the strength of the concrete. Generally, the compressive strength can be greater than 100 MPa. When concrete strength is required or the concrete needs to be exposed to deicing salt conditions, compact concrete self-waterproof products are the best choice.

The water repellent can make water condense on the concrete surface, because of the surface tension of the water, it cannot penetrate into the concrete. The main ingredients of such admixtures are usually stearates or petroleum-based oils. This type of concrete self-waterproof products is very common in ground works, such as prefabricated enclosure panels. Hycrete is a concrete admixture of this type. It can combine with metal ions in the cement slurry to form a water-insoluble polymer. It blocks the micropores in the concrete, preventing water from penetrating into the concrete. Plays an anti-rust role.

Crystal waterproof products are the third type of concrete self-waterproof admixtures. Different brands of crystalline waterproof products have different chemical compositions, but the basic principle is the same, that is, in the presence of water, crystalline waterproof products react with cement hydrated calcium hydroxide and other by-products to produce crystal-filled concrete. Micropores and hairline cracks. This reaction occurs throughout the entire life of the concrete, giving it the ability to self-seal.

2. Advantage

Compared with coatings and coils, self-waterproof technology for concrete has many advantages. For example, self-waterproofing of concrete during backfilling will not wear or damage, nor will it delaminate, which will greatly reduce the maintenance cost of the building throughout its life. If there are large cracks, the crystalline waterproof product can be easily repaired from the inside of the structure. Because it can provide comprehensive and long-term protection, the crystalline waterproof product is very suitable for high-corrosion environments or situations with high requirements on the project. It can reduce the construction volume, improve the reuse performance of concrete, and can be used in some green evaluation systems Score.

3. Application

Concrete self-waterproof products can be applied in various ways. Most products are powdery, some are paste coatings, and some are liquid. They can be sprayed, but the most widely used is to add them to the concrete mixture at the mixing station. In particular, crystalline waterproof products should be used as much as possible in the initial stage of construction.