If it is mixed in too much, it will affect the setting and hardening of the cement, thereby affecting the strength of the concrete
Adding water-reducing agent will increase the slump of the concrete, and excessive addition will cause the concrete to bleed and even segregate.
Theoretically speaking, adding a small amount of water reducing agent will only increase the slump without affecting the water-cement ratio, and the strength of concrete will not be affected. But if it is not handled properly, it will definitely affect the intensity.
The influence on strength can be considered from the following aspects:
1) Test block production. The water reducing agent increases the slump of the concrete, and the concrete is likely to cause segregation and bleeding. This requires very high test block production. If the test block is not made properly, the strength will be reduced.
2) Concrete slump. If the slump of the prepared concrete is less than 200mm, adding less admixture has little effect; if the slump is relatively large, above 220mm, the effect of adding admixtures twice will be greater.
3) Adjust the concrete. If the concrete slump is too small after being transported to the construction site, it is necessary to add admixtures for adjustment. It is stronger than adding water. But it should be noted that the pouring should be completed quickly, otherwise problems such as pump blockage will occur.
Water reducer is a concrete admixture that can reduce the water consumption for mixing while maintaining the slump of concrete basically unchanged.
According to chemical composition, it is usually divided into: lignosulfonate superplasticizer, naphthalene superplasticizer, melamine superplasticizer, sulfamate superplasticizer, fatty acid superplasticizer Water agent, polycarboxylate superplasticizer. What I am talking about here is the type of polycarboxylic acid.
We know that the main factors affecting the strength of concrete are the water-cement ratio and water consumption. Small water-cement ratio (less water consumption)>large water-cement ratio (more water consumption); high strength>low strength This is a corresponding relationship.
In the case of a certain amount of cement, concrete mixed with water-reducing agent is stronger than concrete without water-reducing agent (less water consumption). Water-reducing agent has a positive effect on the strength of concrete. The optimal dosage is too little or too much, which will affect the strength of concrete.
The optimal dosage is based on the manufacturer’s recommended dosage (usually 0.8% to 1.3%). It is necessary to test and mix to actually know how much water-reducing agent affects the concrete strength. The main reason is that the early strength is greatly increased, and the 28d late strength is slow. .