In the process of concrete pouring, often leave expansion joints to cope with the thermal expansion and contraction of concrete, the setting of expansion joints is related to the concrete pouring process, expansion joints are usually set between blocks for concrete poured in pieces, expansion joints are usually cut according to a certain area (such as 6 meters X 6 meters, etc.) for concrete poured in whole blocks, and expansion joints may not be set for concrete of special structure or set for larger areas, such as elastic anti-cracking concrete structure, reinforced concrete structure, etc. For rigid floor coating, such as the substrate concrete cracks due to thermal expansion and contraction, the floor coating is usually cut according to a certain area (such as 6 meters X 6 meters, etc.).
For the rigid floor coating, such as the substrate concrete due to thermal expansion and cold shrinkage cracking, due to the limited elasticity of the floor coating, usually the floor coating is easy to crack, and easy to appear in the cracking of the shell delamination phenomenon, for the concrete has been set expansion joints, although can not completely exclude the possibility of other parts of the cracking, but most of the cracking occurs in the original expansion joints. Therefore, when applying the floor coating, the flooring construction unit should negotiate with the owner to properly treat the concrete expansion joints in order to achieve the expected and acceptable effect for both parties to avoid quality disputes.
There are several treatments for concrete expansion joints when floor coating, each with its own advantages and disadvantages.
- When the flooring is coated, the expansion joints are filled with rigid substances such as epoxy resin mortar (which should be a solvent-free product), and then the whole flooring coating process is carried out according to the flooring, and the expansion joints are not visible on the flooring coating before cracking occurs after the coating is completed.
This method does not guarantee that the floor coating at or near the expansion joints will not crack or crust. Since this type of steel material is not elastic and cannot resist the stresses of concrete shrinkage and cracking, cracking cannot be avoided.
If the owner allows the ground to have uniform and straight expansion joints, it is possible to use a cutting machine to cut 2-5 mm wide expansion joints in the original location of the expansion joints after the floor coating is completed, leaving space for the concrete to expand and contract, which can avoid uneven cracks in the future and reduce the phenomenon of crusting along the cracks in the floor coating.
Usually only in the ground decoration requirements are not high occasions, this way can be accepted by the owners.
- in the flooring coating, the elastic material (such as polyurethane elastomers) will be used to fill the expansion joints, and then painted in the middle coating and topcoat.
This treatment and the first way compared, because the elastomer disperses the stress formed by concrete shrinkage, the possibility of cracking the coating on the expansion joints is greatly reduced, the ground overall color is consistent, but because the coating on the elastomer is still rigid, when the concrete shrinkage is more violent, the floor coating on the elastomer (mid-coat and topcoat) may still crack, but the cracks will not be very large.
When the floor coating is applied, the expansion joints are left as long as possible, and then the polyurethane elastomer is used to fill the joints until they are straight.
- This treatment method in the cleanliness and aesthetic requirements of high degree of electronics factories, pharmaceutical plants, precision instrument manufacturing plant is often used, can basically avoid expansion joints at the floor coating cracking phenomenon, but also more beautiful, the disadvantage is that due to the current polyurethane elastomeric glue color is relatively small (generally grass green and iron red), not easy to achieve and the overall color of the floor coating, at the same time, with the thermal expansion and contraction of concrete, polyurethane elastomeric glue will also appear convex and concave phenomenon.
- local ground expansion joints, but also often used to lay paste glass fiber cloth to enhance the anti-cracking method.
This method can ensure the overall color of the ground, also can resist the cracking caused by the contraction of the concrete is not big, but if the design thickness of the floor coating is too thin, it is not easy to operate, easy to appear patch the ground at the phenomenon of higher than other places.
The above treatment measures are usually only for the expansion joints of the concrete under normal conditions, if the ground settlement and other factors cause a large width of the concrete cracks, the above measures may fail.
In short, in the floor coating coating, the expansion joints should be paid attention to the treatment, as to what kind of treatment, the communication between the construction unit and the owner is necessary, should be carried out after the consensus of both parties.