Brief Discussion on Construction Points of Compensating Shrinkage Concrete

The mix proportion of shrinkage-compensating concrete must be determined by test. 525# Portland cement is generally used, and U E A expansive agent is added according to 8% of cement dosage. When the shrinkage-compensating concrete is mixed, the water-cement ratio of 30% to 50 mm is 0.49, the sand ratio is 32%, and the expansion rate of the concrete is controlled between 0.02% and 0.05%. Reinforced crack-resistant fibers

2. Mixing of Shrinkage Compensation Concrete

Shrinkage compensating concrete should be stirred on site by a forced mixer, and the amount of UEA expansion agent added should be responsible by a special person, the error should not exceed 0.5%. The metering device of UEA expander should be checked regularly and adjusted regularly. The mixing time of concrete is 40 to 50 seconds longer than that of ordinary concrete, and the mixing uniformity is the criterion, that is to say, the material can be discharged only when the mixing uniformity is reached.

3. Setting of Expansion Reinforcement Zone for Shrinkage Compensation Concrete

Expansion reinforcing belt is mainly used to compensate the shrinkage deformation of early concrete. It is required to be set at the place where the deformation stress of concrete is the greatest. Generally, one is set at 60m. Practice: Expansion enhances the bandwidth of 2-3 m, with dense wire mesh arranged on both sides of the belt, and separates the concrete in and out of the belt. The amount of expansive agent added in the reinforcing belt is 10%-12% of the cement content. At the same time, 10% horizontal reinforcing bars are added. They are arranged vertically along the direction of the expansive belt. The two ends of the expansive belt extend 2 m and are connected with the upper and lower (inner and outer) reinforcing bars

4. Treatment of Construction Joints

Horizontal construction joints of civil air defense projects are generally located at 500 on the bottom of the wall and 500 under the roof. A 50 *50 mm groove is reserved in the middle of the wall. The groove should be washed clean, the appendages removed, and no clear water should be allowed. Then the rubber water stop strip should be put in. The rubber water stop strip should be placed straight and evenly, and the overlap length should not be less than 50 mm. After removing the moulds, 200 mm gross is cut up and down along the construction joints, and UEA waterproof mortar is used for four layers of finish.

5. Maintenance and Repair of Shrinkage Compensation Concrete

Compensating shrinkage concrete should be compacted, not leak, poured concrete can not be directly exposed to sunlight, after the initial setting of concrete, it should be maintained by a special person, and the maintenance time should not be less than 14 days.

After removing the formwork, the exposed surface of concrete, especially the outer wall, dries quickly. It must be covered with wet straw mat. If honeycomb linen surface appears, the loose part should be removed, and then the cement mortar with 10% UEA expansive agent 1:2 is used to mend it. For larger honeycombs, exposed stones and exposed bars, weak concrete surface and individual prominent aggregate particles must be chiseled out, washed with pressurized water, and filled with beanstone concrete with 10%-12% UEA expansion agent. Beanstone concrete is one step higher than the original label.

1. Mix ratio of shrinkage compensating concrete

The mix proportion of shrinkage-compensating concrete must be determined by test. 525# Portland cement is generally used, and U E A expansive agent is added according to 8% of cement dosage. When the shrinkage-compensating concrete is mixed, the water-cement ratio of 30% to 50 mm is 0.49, the sand ratio is 32%, and the expansion rate of the concrete is controlled between 0.02% and 0.05%.

2. Mixing of Shrinkage Compensation Concrete

Shrinkage compensating concrete should be stirred on site by a forced mixer, and the amount of UEA expansion agent added should be responsible by a special person, the error should not exceed 0.5%. The metering device of UEA expander should be checked regularly and adjusted regularly. The mixing time of concrete is 40 to 50 seconds longer than that of ordinary concrete, and the mixing uniformity is the criterion, that is to say, the material can be discharged only when the mixing uniformity is reached.

3. Setting of Expansion Reinforcement Zone for Shrinkage Compensation Concrete

Expansion reinforcing belt is mainly used to compensate the shrinkage deformation of early concrete. It is required to be set at the place where the deformation stress of concrete is the greatest. Generally, one is set at 60m. Practice: Expansion enhances the bandwidth of 2-3 m, with dense wire mesh arranged on both sides of the belt, and separates the concrete in and out of the belt. The amount of expansive agent added in the reinforcing belt is 10%-12% of the cement content. At the same time, 10% horizontal reinforcing bars are added. They are arranged vertically along the direction of the expansive belt. The two ends of the expansive belt extend 2 m and are connected with the upper and lower (inner and outer) reinforcing bars.

4. Treatment of Construction Joints

Horizontal construction joints of civil air defense projects are generally located at 500 on the bottom of the wall and 500 under the roof. A 50 *50 mm groove is reserved in the middle of the wall. The groove should be washed clean, the appendages removed, and no clear water should be allowed. Then the rubber water stop strip should be put in. The rubber water stop strip should be placed straight and evenly, and the overlap length should not be less than 50 mm. After removing the moulds, 200 mm gross is cut up and down along the construction joints, and UEA waterproof mortar is used for four layers of finish.

5. Maintenance and Repair of Shrinkage Compensation Concrete

Compensating shrinkage concrete should be compacted, not leak, poured concrete can not be directly exposed to sunlight, after the initial setting of concrete, it should be maintained by a special person, and the maintenance time should not be less than 14 days.

After removing the formwork, the exposed surface of concrete, especially the outer wall, dries quickly. It must be covered with wet straw mat. If honeycomb linen surface appears, the loose part should be removed, and then the cement mortar with 10% UEA expansive agent 1:2 is used to mend it. For larger honeycombs, exposed stones and exposed bars, weak concrete surface and individual prominent aggregate particles must be chiseled out, washed with pressurized water, and filled with beanstone concrete with 10%-12% UEA expansion agent. Beanstone concrete is one step higher than the original label.