The EPA states that free liquids can be placed in a landfill if all of it has been “solidified so that free-standing liquid is no longer observed or has been otherwise eliminated.”1 Some landfills might question the disposal of the solidified slurry because of their unfamiliarity with the material; however, EPA documentation states that is perfectly acceptable for landfills once it is completely solidified.
Furthermore, only certain slurry solidifying brands (such as GelMaxx) are acceptable for landfills because of the Toxicity Characteristic Leaching Procedure (TCLP). This is a sample method for chemical analysis used to simulate leaching in a landfill. In other words, the TCLP determines whether the liquid that excretes from the solids will carry any environmentally harmful substances. Make sure to get a product that encapsulates the heavy metals and keeps the slurry from emulsifying and leeching into the landfill. However, please keep in mind that if the concrete slurry has harmful toxins before solidification, it will still be considered hazardous after solidification.
Now is it legally safe for contractors to dispose solidified concrete slurry directly in the dumpster? Yes, because it abides by all the EPA standards for proper liquid waste disposal.
 Authenticated US Government Information, p. 473. http://www.gpo.gov/fdsys/pkg/CFR-2010-title40-vol25/pdf/CFR-2010-title40-vol25-sec264-314.pdf
Paul Nguyen, Marketing & Sales Associate with GelMaxx Slurry Solutions www.gelmaxxusa.com
Q: What can be done to take away discoloration from screed lines, disparate aggregate sizes, and rust or tile stains when grinding to prepare for polished concrete on a new or existing slab?
A: Unfortunately there is no guarantee that grinding can remove any difference in concrete coloring. The contractor/owner must be aware of this from the onset of any project.
Common causes of color variation can be rust stains or VCT stains that leave a grid-like pattern in the concrete after the contractor removes the old tile. Other variations may be exposure of aggregates and sands in the concrete slabs that are unfavorable to the owner or architect. Also, though considered very hard, concrete is actually like a sponge. Stains like rust and oil-based contaminants can seep into concrete 14 inch or more. A 14 inch of concrete would be an expensive amount of concrete to remove if a customer is only budgeting for a “sand” type polish, possibly making the project uneconomical to achieve. Inequalities in aggregate sizes and concentration would, for the same reason, be uneconomical and still not achieve the desired result.
The only way to determine that a satisfactory result can be reached is to perform a mock-up, which is doing the proposed process on a given slab that will be a representation of the area to be ground and polished. This will give the applicator and owner the best guide of what can be achieved with the in-place slab, thereby dictating the process that must be used, and also, that the customer’s expectations can be met before any further work is done. This is the surest way to meet the customer’s expectations after the sales process is complete but before the expensive phase of installation begins.
Josh Jones, President Substrate Technology, Inc. www.substratetechnology.com
Q: I followed your data page exactly. Why isn’t your densifier working?
A: As a manufacturer of products for the finished concrete industry, this question hits my desk at least three to four times a week. When we (manufacturers) develop a product, we go through a very long and lengthy process before introducing it to the market. We hold weeks and months of testing, not only in our lab but also in field trials with applicators. When we launch a product that has passed all of these steps, we take great pride in the fact that it has been “field tested, with laboratory results backing it.” But like all products in all industries, we cannot count on everything to be perfect all the time.
When I receive this distress call, the first step in solving this is to gather information from you, the contractor. Since each jobsite is different and since we have different climates and conditions throughout the country and the world, here are a couple of suggestions and tips to go over.