Various CSA cement brands and manufacturers

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.

csa_compressive_graph

Note that there used to be another CSA additive called Qwix. Buzzi Unicem CSA can be used exactly like Qwix.

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