The second advance is calcium sulfo-aluminate (CSA) cements. Developed in China in the 1970s for the rapid fabrication of concrete pipe, CSA cements surpass ordinary portland cement in many categories.
Portland cement is the usual binder in concrete. Most of the problems and challenges with concrete come from the portland cement. Portland cement gains strength slowly, has a tendency to shrink (and therefore cause cracking or curling of the countertops), and has a significant carbon footprint.
A well-designed portland cement-based concrete countertop mix might achieve a compressive strength of around 4,000 to 5,000 psi in four to seven days. CSA cements often achieve this strength in less than 24 hours. Some mixes can achieve this in a mere four hours. CSA cements also have a lower porosity than ordinary portland cement, so they are more shrink-resistant.
This means concrete tops made with CSA reach production strength in hours rather than days and turnaround time can typically be cut in half. The higher cost of the cement is offset by a more efficient and rapid production schedule.
Finally, CSA cements are “greener” than portland cement, meaning they have a much smaller carbon footprint, generating 62 percent less greenhouse emissions during production.
The third advantage addresses the key weakness of concrete: It needs to be sealed in order to be resistant to common household spills and stains. The difficulty with sealers for concrete countertops stems from the fact that they completely define the look, feel and long term performance of the countertop. Sealers determine how stain-resistant a countertop will be. They dictate the sheen, scratch resistance, heat resistance and ability to repair of the finished countertops. Finding a sealer that looks and feels good; provides good stain, scratch and heat resistance; is easy to apply; is quick to cure; and can be easily repaired has been the goal of concrete countertop fabricators for years.
Sealing is important and can be time-consuming. This step can take a day or two to complete and some finishes aren’t fully cured for a week or more, leaving the countertop vulnerable.
Sealer application can be by rolling, spraying or wiping on, depending upon the type of finish. Most sealers suffer from one factor: The final look is dependent upon how the finish was applied. Spraying yields nearly flawless finishes. But spraying requires sprayers, a clean area to spray and skill and willingness to do so. Rolling always leaves some marks, and thicker finishes can’t be wiped on with a microfiber cloth. No one wants a high-performance finish that looks like it was put on like house paint. The new ultraviolet light (UV) cured finish eliminates nearly all these compromises.
The finish itself is a single part, zero VOC finish. It provides excellent stain and acid resistance. Acid from lemon juice, vinegar or even straight muriatic acid will not damage it. For a coating, it has very good scratch and heat resistance. The finish can be dead matte, high gloss or anything in between.