Views: 32 Author: Site Editor Publish Time: 2020-01-09 Origin: Site
Concrete has many characteristics, including low price, high wear resistance and durability, and multiple sources of materials. The application of construction engineering to it is very extensive, but during the construction of concrete pavement, because of various reasons, the peeling phenomenon of concrete pavement often occurs, then what is the cause of the peeling problem of concrete pavement?
The main causes of peeling problems on concrete pavement include two aspects: concrete material factors and construction factors.
1.Concrete material factors
(1) The particle size of the sand is too small, and the mud content is too large
Because fine sand has large shrinkage and close water demand, it also has poor water retention performance. Therefore, during the solidification of concrete, it is difficult for cement and fine sand to bond, which seriously reduces the strength of the concrete surface. In addition, the degree of bleeding of concrete will become more and more serious as the particle size of the sand becomes smaller. When there is too much mud content in the concrete, there will be cement particles in the concrete, the concrete setting time and cement hydration time will delay the serious reduction of the strength of the concrete surface, and then cause the phenomenon of peeling of the concrete pavement.
(2) Use agglomerated, damp, expired cement or low strength cement
The strength of concrete is determined by the strength of cement. If effective preservation measures are not taken, or the cement used is too inferior, it will severely reduce the strength of the cement, which in turn will cause the strength of the concrete to decrease and cause peeling. When the cement is agglomerated, damp and other bad phenomena, it is very easy to appear uneven concrete mixing phenomenon, local agglomeration phenomenon, uneven concrete setting time, resulting in decreased concrete abrasion resistance, hardness, strength, and then cause peeling phenomenon .
(3) High water-cement ratio of concrete
Due to the effect of gravity, particles with a relatively large diameter in the concrete will sink to the bottom of the concrete under its own gravity, and particles with a relatively small diameter will be suspended in the upper part of the concrete. The surface of concrete is mainly water, and the above phenomenon is the so-called bleeding phenomenon. The bleeding phenomenon can only be reduced, it cannot be completely eliminated. The bleeding phenomenon becomes more serious with the increase of the concrete water-cement ratio, and more and more water will accumulate on the concrete surface layer, and eventually a floating layer will be generated on the concrete surface. The amount of water in the slurry layer is relatively large, the strength is relatively low, and the abrasion resistance is poor, which may cause peeling.
(4) The proportion of concrete does not meet the requirements
Before mixing the concrete, the weight of the concrete raw materials was not accurately weighed, which caused the concrete ratio to be inconsistent with the specified requirements. In order to facilitate the transportation of commercial concrete in the pipeline, water was added to the mixing truck to dilute it, thereby increasing the water-cement ratio, resulting in The change of the concrete proportion causes the phenomenon of peeling on the concrete surface.
(5) Segregation of concrete occurs during transportation
After the commercial concrete is transported to the construction site, the slump of the commercial concrete should be tested. When segregation occurs during the transportation of the concrete and the concrete slump does not meet the specified requirements, it should be stirred once before pouring the concrete. After mixing the concrete, the slump of the concrete is still not up to the standard, and the peeling of the concrete surface will occur.
2. Construction factors
(1) Calendering is not performed before initial setting
According to the requirements of relevant technical regulations, before placing the concrete, it should be smoothed with a trowel, and before the concrete is initially set and final set, it should be wiped again. After vibrating, concrete will appear on the surface of the concrete. Because the strength is too small, the concrete and the concrete layer will separate, and peeling will occur. If calendering is performed prematurely, the bleeding channel will be blocked, and a bleeding layer will be generated below the surface layer, causing the epidermis to fall off. Because the water evaporation rate of the surface of the concrete is much higher than the rate of bleeding, if there is no rubbing during initial and final setting, the surface of the concrete will shrink due to excessive water loss, resulting in dry cracking and peeling. If it is too late, When the plastering is carried out, the concrete has finally settled. If the plastering is excessive, the concrete structure will be severely disturbed, which will greatly reduce the strength of the concrete surface and cause peeling.
(2) Excessive vibration of local concrete
In order to make the concrete compactness higher, the mixing more uniform, and the bleeding phenomenon to be effectively alleviated, it is often necessary to vibrate the concrete. When the concrete surface is flat and scum appears, the vibration of the concrete can be stopped. During the construction process, the construction personnel often leave the vibrating rod in the vibrating place for a long time, and the phenomenon of excessive vibrating will occur, which will cause the phenomenon of bleeding and segregation of the concrete, and eventually the peeling of the concrete pavement.
(3) Water accumulated on the concrete pavement foundation, and excessive watering
When there is a lot of accumulated water in the foundation of the concrete pavement, when the concrete is vibrated, the bleeding phenomenon is extremely easy to occur. The water-cement ratio of the surface concrete is greatly increased, and the concrete pavement will appear peeling. In order to facilitate the smoothing and calendering of the concrete pavement, the construction workers often sprinkle a lot of water on the concrete surface, thereby increasing the water-cement ratio of the concrete surface, reducing the strength of the concrete, and causing skinning. In order to facilitate the paving of concrete, construction workers often add a large amount of water to the concrete, resulting in a decrease in the strength of the concrete, a very serious bleeding phenomenon, and a peeling phenomenon.
(4) Failure to perform maintenance of concrete pavement
To create an environment with suitable humidity and temperature to prevent premature freezing and evaporation of water in the concrete, which is the purpose of concrete pavement maintenance. Within 12 hours after the concrete is finally set, effective maintenance measures should be taken on the concrete pavement, such as sprinkler measures, pavement cover measures, etc. In the early stage of concrete pavement maintenance, the concrete hydration rate is relatively fast, requiring more water demand and watering times. When the external environment temperature is relatively high, the watering times should be increased to ensure that the concrete road surface is wet. Because the concrete surface hydration speed is very fast, once the timely watering is not carried out and the water is not replenished in time, the concrete pavement is very prone to dry cracking and shrinkage, which eventually causes the pavement of the concrete pavement. In addition, premature watering will not work. If the concrete surface has not yet completely solidified, the concrete pavement will be watered and cured, which will cause the concrete's water-cement ratio to increase and cause peeling.
(5) Open before the concrete pavement strength reaches the standard
Before the strength of the concrete pavement is not up to standard, especially when the brittleness of the concrete surface is very high and the degree of internal adhesion of the concrete is relatively poor, once the heavy-duty vehicle passes through the concrete pavement, the concrete surface is extremely likely to be damaged, causing peeling. If the car tire contains some hard materials, such as stones, the concrete pavement will be crushed.
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