What is the correct way to use expander?

Many people may not know about expansion agents, let alone have used them. In fact, expansion agents are widely used. For example, they are widely used in the production of materials or in the field of silent explosions. The most common ones are concrete expansion agents, and there are also refractory expansion agents and so on. When using expansion agents, you must be particularly careful and master the relevant technical essentials, especially the following usage methods.

First, the use of expansion agent

1. Scientifically and reasonably select the dosage of expansion agent. The selected expansion agent must be adapted in the corresponding concrete mixing station. The main purpose of adaptation is to determine the reasonable dosage and incorporation method based on the design expansion rate index. There are usually two methods of incorporation: external incorporation and internal incorporation to replace part of the mineral admixtures.

2. Control the temperature of concrete when pouring into the mold. Generally, it is more reasonable to keep it in the range of 30±5℃.

3. Strengthen the vibration of concrete, making it denser than ordinary concrete.

4. Scientific and reasonable maintenance methods: Strengthen maintenance 7 days before pouring. Watering should be done at least 5 times between 10 am and 4 pm every day. Maintenance should be carried out once in the morning and once in the afternoon on the 8th to 14th days. It is not advisable to carry out watering maintenance at night, and it is not advisable to carry out excessive maintenance in winter. It is very important to strictly combine temperature monitoring with maintenance, and keep in mind the temperature control principle of "cooling down during the heating up stage and keeping warm during the cooling stage".

5. It is not advisable to use sand and gravel with too high mud content to produce concrete, and it is not advisable to load the concrete too early.

Second, the type of expansion agent

1. Calcium sulphoaluminate

This type of expansion agent includes: alunite expansion agent (the main components are alunite and anhydrous gypsum or dihydrate gypsum); CSA expansion agent (the main component is anhydrous calcium sulfoaluminate); U-type expansion agent (the main components are anhydrous calcium sulfoaluminate, alunite, gypsum), etc.

2. Calcium oxide expansion agent

There are many methods for preparing this type of expansion agent, such as adding an appropriate amount of gypsum and water-quenched slag to lime calcined at a certain temperature; mixing quicklime with stearic acid; grinding limestone, clay, and gypsum into clinker powder at a certain temperature and then mixing it with finely ground gypsum calcined at a certain temperature, etc.

3. Metal expansion agent

Commonly used iron chip expansion agents are prepared by adding an appropriate amount of oxidant (such as perchromate, permanganate, etc.) to iron powder.

Third, the role of expansion agent

1. Underground buildings: such as subways, underground parking lots, underground warehouses, tunnels, mines, civil air defense projects, foundation pits, mixing stations, etc.

2. Pools, swimming pools, water towers, storage tanks, large containers, granaries, oil tanks, cave warehouses, etc.

3. High-strength highway pavement, bridge concrete surface, culverts, etc.

4. Anchoring of prefabricated components, frame structure joints, pipe joints, grouting materials for post-tensioned prefabricated components, backfilling of post-cast joints, and magma grouting materials

5. Cement products: self-stressed, prestressed and steel-jacketed prestressed concrete water pipes, floor slabs, columns, beams and columns, waterproof roof panels, etc.