Can the slump of concrete be adjusted by secondary addition of concrete admixtures?

Can the slump of concrete be adjusted by the secondary addition of concrete admixtures? The slump of commercial concrete is small after it is transported to the site. It can be adjusted by adding about 20 kilograms of water. The strength will not be affected much. If you want to add admixtures, you must add There are only water-reducing admixtures, but the amount cannot exceed the total amount of admixtures in the entire vehicle.

You can do a test in the laboratory by adding water on site. After the trial mixing, leave it for 2 hours, and then add water to the initial slump to do a comparative strength test. In this way, the laboratory will have confidence. Any operation in the laboratory must be based on testing. Others can only be a reference.

For concrete with rapid slump loss over time, adding the same water-reducing agent twice is actually a commonly used method. Relevant standards and specifications also allow it, because the water-cement ratio is not changed and has no significant impact on strength.

The concrete tank truck should have a corresponding water-reducing agent adding device, which is specially used for the secondary addition of water-reducing agent. The amount of the same water-reducing agent added for the second time must be controlled. After addition, the tanker must be rotated rapidly for a period of time to ensure that the water-reducing agent is evenly mixed.

Concrete slump can be measured visually if you have experience. It depends on where the concrete is used. For example, if pumping is used to build a building, the slump should be larger. If dumping is used to pave the road, the slump should be smaller.

Concrete admixtures depend on the season. In winter, because the temperature is low, early strength additives must be used. In summer, the temperature is high and water evaporates quickly, so retarder must be used to reduce slump loss.

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If there are anti-abrasion requirements, you need to add fiber and other anti-abrasion materials

A small amount of antifreeze should be added during winter construction

A small slump indicates that your Concrete has poor fluidity. To determine whether to add water or concrete admixtures to concrete, it depends on your concrete mix ratio. If the water consumption is large, the only way to ensure the strength of the concrete is to increase the amount of admixtures. If the water-cement ratio is relatively small, you can increase the water consumption appropriately. If you add 40Kg more fly ash, it will be more viscous, so you should be able to increase the water consumption

If the concrete is too thin, adjust the water first to reduce the water consumption, which can improve the strength of the concrete. If the concrete is thin and there is a phenomenon of bottoming out, you can reduce the admixtures, or you can also slightly reduce the water and admixtures. The key is to adjust the concrete to have good workability and fluidity. If the concrete is dry, the amount of admixture should be increased and the amount of water should not be increased as much as possible to ensure the strength of the concrete.

If the water consumption is too small, causing the concrete to dry out, just adding admixtures will not achieve a good-looking effect?

When the concrete is too thin and the slurry has poor viscosity, In this case, reduce water consumption first. But don't drop it too much. You can first drop the water cement by 1 point and mix it. If the concrete is too thin and there is a phenomenon of bottoming out, you can reduce the admixture by 1 point. This is to solve the problem of too thin concrete. When the concrete is dry, adding water depends on whether the water-cement ratio of the concrete mix is ​​too high. If it is not too high, you can increase the water-cement ratio. If the water-cement ratio is large, the amount of concrete admixtures should be increased to achieve the fluidity and workability of concrete, which can ensure the strength of concrete. The concrete made with additives does not look good. The problem may be in your mix ratio. You can increase the sand rate by 1 point and try mixing it. Do not increase water consumption.

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