Concrete itself is a porous structure. In order to ensure the pumpability and durability of pumped concrete, concrete defoaming agents are often added during construction to improve this feature. There are often "honeycomb pits" in concrete. ". Some of its formations are bubbles and some are blisters. Concrete defoamer can solve this problem to a certain extent. The holes formed by water bubbles are oval-shaped, and the holes formed by bubbles are mostly irregular. Concrete must be vibrated during the pouring process. Local liquefaction will cause water to precipitate and gas to float. When the water and bubbles are enriched in the accumulation area or upper part, the water and bubbles precipitated during the concrete solidification process will form defects.
When the bubbles appearing on the concrete surface are larger than the specification requirements, it will have the following effects on the concrete:
1. Reduce the strength of the concrete structure: Due to the larger bubbles, the strength of the concrete is reduced. The cross-sectional volume causes the inside of the concrete to be less dense, thereby reducing the strength of the concrete.
2. Reduce the corrosion resistance of the concrete structure: Due to the large number of bubbles appearing on the surface of the concrete defoaming agent, the effective thickness of the steel protective layer is reduced and the process of carbonization of the concrete surface is accelerated.
3. It seriously affects the appearance of concrete.
Since the polycarboxylic acid mother liquor itself has a large gas content, bubbles will occur in the concrete. If the defoaming agent is combined with the polycarboxylate water-reducing agent, many large bubbles in the concrete will be eliminated, effectively alleviating the adverse effects of foam on concrete and improving production efficiency. These are issues of considerable concern
The following points should be noted when using concrete:
1. When the defoaming agent is used in the production of concrete with polycarboxylate series water-reducing agents, it will reduce the air content of the polycarboxylate water-reducing agent and the concrete slurry. It feels sticky. It is recommended to add air-entraining agent after adding defoaming agent to eliminate the uneven large bubbles in the polycarboxylic acid and introduce uniform small bubbles, which can increase the ease of concrete.
2. The defoaming agent has strong dispersion with water and additives, and is prone to separation after being left for a long time. It is recommended to stir continuously during this period.
3. The performance of defoaming agents may be reduced due to alkalinity. Please avoid using it when the pH value is above 10.
Defoaming mechanism of concrete defoaming agent
Adding defoaming agent to concrete can prevent the generation of bubbles in the concrete mixture or reduce the original bubbles. The defoaming agent added in the experiment is a surfactant that can reduce the surface tension of the liquid phase. When the wetting angle is reduced to a certain extent, the bubbles will break away from the adsorption on the solid surface and escape or burst, so defoaming is added. The agent can eliminate bubbles in concrete to a certain extent, effectively prevent or eliminate honeycombs and pitting on the surface of concrete, make the surface of concrete have higher flatness and gloss, and improve surface properties.
Defoaming has two main meanings. One is "breaking foam", which is to eliminate the foam that has been generated; the other is "suppressing foam", which is to prevent the regeneration of foam. Defoaming agents with excellent performance often have both excellent foam-breaking and foam-suppressing abilities.
The above is the relevant knowledge about concrete defoaming agents. I hope it will be helpful to you.
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