Concrete surface retarder is a brushing paste surface retarder. It is an environment-friendly aqueous product prepared by a variety of cement retarding active components. It can be directly painted on the formwork to greatly delay the setting of concrete surface. When the internal concrete reaches sufficient strength, the concrete surface can be easily washed off with water due to the delay of setting, so as to expose the internal aggregate.
GENERAL
Concrete surface retarder is a brushing paste surface retarder. It is an environment-friendly aqueous product prepared by a variety of cement retarding active components. It can be directly painted on the formwork to greatly delay the setting of concrete surface. When the internal concrete reaches sufficient strength, the concrete surface can be easily washed off with water due to the delay of setting, so as to expose the internal aggregate.
Scope of application
◆Concrete surface with exposed aggregate is required for the 
connection surface of prefabricated components in the field of prefabricated buildings;
◆Connecting surfaces of precast concrete panels such as bridges;
◆Exposed aggregate permeable pavement.
FEATURE
Product features
◆Water based products, safe and environment-friendly, easy to operate.
◆Applicable to different site conditions and formwork surfaces, including steel formwork, bamboo plywood and wood formwork. It is unnecessary to roughen the concrete surface by mechanical methods such as iron cone or chisel, so as to greatly reduce the labor intensity and save the construction cost.
◆The thickness / etching depth of retarding concrete (which can be adjusted as required) can be up to more than 10mm.
◆Do not reduce the strength of the concrete body and the holding force to the reinforcement.
◆No corrosion to steel formwork and reinforcement.
◆Good surface retarding effect can also be achieved for steam cured concrete.
PERFORMANCE
Performance metrics
| Testing items | Technical index | |
| Appearance | Homogeneous milky paste | |
| PH | 6~8 | |
| Open working hours (h) | ≥10 | |
| Etching depth | 1~10mm | |
| Final strength of concrete | No effect | |
| Storage stability | No delamination and caking during storage | |
| Retarding time (h) | Normal temperature | Not less than 72h |
| 60℃ | Not less than 12h |
Construction process
◆On the concrete formwork with rough surface, brush a layer of surface retarder with a brush.
◆Pour the concrete and vibrate it tightly. At this time, the surface retarder will be immersed into the concrete on the contact surface.
◆Remove the formwork after the concrete strength reaches the strength required for formwork removal, and the formwork removal time shall not be longer than 7 days.
◆Wash the non coagulated concrete surface with high-pressure water gun to expose the aggregate and reach the designed etching depth.
◆The dosage under normal temperature is generally 0.2 ~ 0.5kg/m2, and the specific dosage shall be determined through tests according to factors such as concrete strength grade, curing temperature, etching depth, formwork removal time and construction temperature.
Notes:
1. The mold surface must be cleaned before application, and there shall be no oil stain on the mold surface and release agent can not be applied. The oil stain needs to be completely cleaned and it can be coated with plain cement slurry for several times on site until the it is completely cleaned.
2. The depth of exposed material (etching depth) is related to many factors, such as the amount of retarder used on the concrete surface (coating thickness), the length of concrete curing time, the curing temperature, the strength of concrete, the variety and dosage of cement, the variety of concrete admixture and so on. The specific data need to be determined through experiments to achieve the best effect.
3. Under the same conditions, the thicker the surface retarder is applied and the deeper the etching is and the more exposed the aggregate is.
4. After formwork removal, it shall be washed with high-pressure water gun as soon as possible and cleaned to ensure that there is no residual retarder on the surface of prefabricated components.
5. It is recommended that the pressure of the water gun should be 6 ~ 8Mpa, the water gun should be flush against the component surface, and the distance between the water gun and the component surface to be flushed should not be greater than 50cm.
6. Avoid flushing after the components are placed for several days after the formwork is removed, otherwise, the flushing efficiency will be reduced and even the etching depth will be affected.
Packaging and storage
Packed in barrels, 10kg per barrel. This product should be kept away from light at - 5 ~ 30 ℃, and the shelf life is 6 months. If the storage time is long, it shall be mixed evenly before use.
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