In a previous article, I explained basic principles of concrete countertop mix design, such as the role of sand, cement, water, water-cement ratio and aggregate gradation. Click here to read that article and view the videos.
In this article, I provide details about two important specialty admixtures for concrete countertop mixes: superplasticizer and viscosity modifier. These admixtures work hand in hand to create the right mix consistency without compromising strength by adding water.
Polycarboxylate superplasticizers are a very powerful type of high range water reducer. This video shows how adding a small amount of a powerful water reducer, instead of water, can take a concrete mix from dry and crumbly to flowable.
Here is a video that demonstrates the dramatic effect superplasticizer has on mix consistency, then explains the science behind how it works.
The video uses a powdered superplasticizer, BASF’s Melflux 2651, in order to demonstrate that it is not the liquid in the superplasticizer that causes the increase in slump. Melflux 2651 is very difficult to find in reasonable quantities for a concrete countertop maker. Buddy Rhodes Concrete Products offers a similar powdered superplasticizer. However, powdered superplasticizers are extremely powerful and very easy to overdose. For that reason, we recommend and sell a liquid superplasticizer, ADVA Cast 555.
ADVA Cast 555, manufactured by Grace and packaged by Buddy Rhodes Concrete Products, is a powerful high-range water-reducing admixture (superplasticizer) based on the next generation of polycarboxylate technology. ADVA Cast 555 is designed for use in precast, ready-mix and self-consolidating concrete (SCC) applications, and it is excellent for use in GFRC.ADVA Cast 555 provides excellent early compressive strength, faster setting strengths and fluidity in mix designs with substantially reduced water content.
The following seminar excerpt explains what viscosity modifying admixtures do. VMAs are used to reduce the slump of concrete, essentially performing the opposite of a high range water reducer (superplasticizer). They also help prevent segregation in aggregate-based mixes.
Fritz-Pak’s Super Slump Buster is an easy to use, powdered viscosity modifying admixture (VMA).It is available in 8-oz bags, which is enough for dozens of average concrete countertop projects. VMA should not need to be used for every project, as explained below.
The manufacturer sells Super Slump Buster only in cases of 60 bags. We sell it by the bag.