Tips of application of polycarboxylate high-performance water reducer(IV)： Issue of Sand Content with Clay & Air-Entraining Properties
1.On Sand Content with Clay
When the sand content contains a high amount of clay, the water reduction rate of Polycarboxylate Superplasticizer will significantly decrease. The solution for using naphthalene-based superplasticizers is often to increase the dosage, whereas for Polycarboxylate Superplasticizer , the change is not significant when the dosage is increased. In many cases, when the fluidity has not yet reached the requirements, the concrete has already started to bleed. At this time, adjusting the sand ratio, increasing the air content, or adding thickeners will not be very effective. The best solution is to reduce the clay content.
2. On Air-Entraining Properties
During the production process of Polycarboxylate Superplasticizer , some surface-active ingredients that reduce surface tension are often retained, making it have a certain air-entraining property. These active ingredients are different from traditional air-entraining agents. In the production process of air-entraining agents, certain necessary conditions for producing stable, small, and closed bubbles are considered, and these effective ingredients are added to the air-entraining agents, so that the bubbles brought into the concrete can meet the requirements of air content and will not have adverse effects on strength and other properties.
The air content in Polycarboxylate Superplasticizer during production can sometimes be as high as about 8%. If used directly, it will have a negative effect on strength, so the current practice is to first defoam and then introduce air. Defoaming agents are often provided by the manufacturers, while air-entraining agents sometimes need to be selected by the users themselves.
