Calcium Sulfo Aluminate Cement (CSA)
The “CSA SYSTEM” is based on incorporation of Calcium Sulf Aluminate Cement in a variety of mix designs. CSA can be used on its own (with a Lithium accelerator), or with an Anhydrite, ordinary portland cement, metakaolin or a combination of these. The CSA system has the benefit of being readily adaptable to suit many different applications where both rapid set and / or high early strength gain are required.
CSA makes a composite cement which exhibits controllable rapid setting and high early strength development ( with little or no loss of late strength). Within CSA systems ettringite formation is typical. Ettringite is an expansive crystalline substance formed when sulfate reacts with tri-calcium aluminate (C3A) and calcium hydroxide (CaOH2). It occupies roughly twice the volume of the original compounds so a controlled expansion occurs. In the CSA system, 85% of the ettringite is developed at a very early stage in the process, before the aluminates and silicates start to hydrate. The risk of late ettringite formation is very limited. Therefore the ettringite which is formed is very stable over time, resulting in reduced cracking and higher strengths.
Depending on the level of addition of calcium sulfate, either shrinkage compensation or positive expansion can be achieved in mortars and concretes. Further potential advantages of CSA systems are improved sulfate resistance, low permeability, enhanced durability and good workability at low temperatures.