Causes and control methods of pores on concrete surface
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Update time : 2023-08-23 17:03:41
In the process of concrete forming, due to the constraints of technology, material, environment, and other conditions, it is easy to lead to bubbles on the surface of concrete. Too many bubbles will bring a series of problems.
Reduce the strength of concrete structure: due to the large air bubbles, the cross-section volume of concrete is reduced so that the interior of the concrete is not dense, thus reducing the strength of concrete.
Reduce the corrosion resistance of concrete structure: due to the appearance of a large number of air bubbles on the concrete surface, the effective thickness of the steel bar cover is reduced, and the carbonization process of the concrete surface is accelerated.
Seriously affect the appearance of concrete
The source of stomata 1.From the concrete itself
The air content of concrete is high, so the bubbles carried by itself migrate to the surface of the member.
From the vibration of the formwork
When pouring concrete, bubbles are produced due to the high-frequency vibration of the formwork. 2.Derived from water
Blisters produced by undispersed free water.
Control the amount of air bubbles inside the concrete.
When fresh concrete is mixed, a large amount of air will be introduced, forming pores of different sizes inside the concrete. 1. Use concrete with a reasonable distribution
The voids of concrete can be reduced by selecting gradation with reasonable sand, stone, rubber, and other raw materials to form a close accumulation. Thus the production of air bubbles in concrete can be reduced.
In addition, the ambient temperature also influences the quality of the surface layer of the concrete structure.
For example, if too many admixtures are added in winter construction, it can easily cause bubbles not to be discharged. 2. Optimization of air entraining agent and defoamer
The air-entraining agent + defoaming agent in the water reducer is optimized to control the number and diameter of air bubbles in concrete to reduce the influence of internal air bubbles on the surface appearance of concrete.
The air-entraining agent + defoaming agent in the water reducer is optimized to control the number and diameter of air bubbles in concrete to reduce the influence of internal air bubbles on the surface appearance of concrete. 3. Optimize the water reducer to control fluidity and workability
Select the appropriate concrete superplasticizer to control the fluidity and workability of concrete into the mold so that the internal pores of concrete can be discharged effectively during vibration.
Control the generation of pores on the surface of the concrete.
Prevent all kinds of holes from showing on the concrete surface. 1. Clean up the template
Clean the formwork according to the construction code to avoid stagnant water and other impurities and ensure the cleanliness of the formwork surface. 2. Reasonable vibration
When pouring concrete, select the appropriate vibration equipment, control the vibration time, vibration radius, vibration frequency, and rod lifting speed, and vibrate orderly and regularly according to the correct operation process.
As far as possible, the air bubbles inside the concrete are discharged by vibration, but the vibration produces new bubbles. 3. Suitable release agent
Select the concrete release agent that matches the concrete, and spray according to the correct operation mode:
A suitable water-based release agent is selected, and using an oily release agent can easily lead to the accumulation and enlargement of pores on the surface of the template and make it difficult to discharge.
It is recommended to use softened or tap water with low electrical conductivity to avoid the inactivation of water-based release agents caused by metal ions such as calcium and magnesium.
Fully stir after mixing with water so that the components of the release agent are fully dispersed evenly, and the proportion of water should not be too high or too low according to the proportion recommended by the manufacturer.
Spray evenly, avoid leakage, and avoid spraying too thick.
After spraying the release agent, the concrete can not be poured until the white fades away.
Avoid Rain Water rushing after spraying and try to pour concrete within 24 hours after spraying.
Control the production of blisters.
Prevent all kinds of holes from showing on the concrete surface 1. Control water consumption of fresh concrete
The water consumption of fresh concrete is strictly controlled, and the material can be discharged only after mixing evenly in the mixer. 2. Control the use of water during pouring
In the process of concrete from machine to pouring, mixing external water into concrete caused by various factors such as Rain Water, spraying water, artificial water, and so on should be strictly controlled.
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