for Concrete Admixture Formulations
Defoamers are crucial components in the formulation of polycarboxylate ether (PCE) superplasticizers. One side-effect of using a PCE superplasticizer is that they pull an excess of air into the concrete slurry. Conventional defoamers, such as non-ionic surfactants with low HLB values, silicon derivatives, dibutyl phosphates and alkyl phtalates are generally added to reduce the amount of air in the concrete. These defoamers may not be compatible with the polycarboxylate ether solution and this can lead to the formation of a hazy product which can then separate, usually on top of the PCE superplasticizer solution.
As a result of this insolubility, the concrete industry has been forced to use separate tanks to store the PCE superplasticizer solution and the conventional defoamer. The two components are only mixed immediately before they are incorporated into the concrete slurry. An alternative to separate storage would be to premix the PCE superplasticizer solution and the conventional defoamer in a tank that is stirred continuously to prevent the base separation of the two components.
Included in our range is a speciality defoamer for use in conjunction with PCE superplasticizers called DEHSCOFIX® WL660.
Unlike conventional defoamers, it can be mixed with PCE superplasticizers in the desired ratios in advance. The result is a crystal clear, isotropic solution that has the required shelf life. It is recommended that the amount of DEHSCOFIX® WL660 is from 5wt% to about 10wt% based on the active weight of the PCE superplasticizer solution.