Currently there are two manufacturers of calcium alumino silicate (CSA) cement products in the United States: CTS Rapid Set® Cement and Buzzi Unicem. Though they are both called CSA cement, the products are not the same, nor do they yield similar strength concrete for a given age.
CTS manufactures Rapid Set® brand cement, which is a CSA cement that is used alone and is not made with nor blended with Portland cement.
Buzzi Unicem USA makes a CSA cement additive simply called “CSA”, but on their website it’s clear that it should be used with Portland cement:
“CSA® is a hydraulic, cementitious binder (per ASTM C219), high in Calcium Aluminum Sulfate Crystals. When used with Portland cement concrete, CSA generates a strong cementitious matrix that enhances the physical and chemical properties of the mix.”
In this regard this “cement” is really a cement additive. It cannot be used at a 100% replacement for portland cement; the recommended replacement rate is 5% to 20%.
In April 2009, The Concrete Countertop Institute conducted standard concrete compression tests to compare the early compressive strength of concrete cylinders made using CTS Rapid Set® cement and Portland cement. Buzzi Unicem CSA was not tested, since it is a CSA additive, not CSA cement. At the time, another 100% CSA cement was available, Ultimax Gray cement. This product is no longer available.
Cylinders made using Rapid Set® and Ultimax Gray cement used only those products; cylinders made using ordinary Type 1 Portland cement used a blend of 90% (by weight) gray Portland cement and 10% VCAS pozzolan. All cylinders were prepared (C192) and tested (C39) in accordance with ASTM guidelines. All concrete cylinders used the same aggregate-based concrete mix design with water-to-cementitious ratios of 0.35 and a CSA retarder dose of 0.5%. (The retarder used was Ultimax Delay, which is no longer available. See this article on retarding CSA cements.) Concrete compression tests were performed at 1, 3 and 7 days after casting.
CCI compression strengths are similar to or even a bit higher than strengths advertised by Rapid Set and Ultimax on their websites. Data for Portland cement and VCAS are shown for comparison purposes.
Note that there used to be another CSA additive called Qwix. Buzzi Unicem CSA can be used exactly like Qwix.