Amorphous Calcium Aluminate (ACA) cement accelerants provide advantages to producers such as very fast setting, notable early and late strength gain, and a white color making them ideal for light castings. The main phase is C12A7 (mayenite) and increased sulfate leads to early ettringite crystal formation in a Portland cement matrix, resulting in extremely high early strengths. ACA cements develop strength similarly to Calcium Sulfoaluminate cements through early ettringite formation. Depending on the loading amount, ACA cements provide faster setting, rapid hardening, drying, and high early and late strength gains even in colder weather.

1. Amorphous Calcium Aluminate
or ACA cement accelerants present unique advantages to the producer:
Very fast setting, notable strength gain both early and late, and by being almost white in
color, they are ideal for light castings.
Main phase is C12A7 (mayenite) and by increased amount of sulphate the formation of
early ettringite crystals in a matrix with Portlandcement leads to extreme high early
strengths.
The mechanism of strength development is through the early formation of ettringite in a
similar way as Calcium Sulfoaluminate cements work.
Depending on the loading on cement (typically 5% to 20%) faster setting , rapid
hardening , rapid drying , Hugh early and late strength gain , even in colder weather.
CALTRA US offers two types of ACA , SC-A and XT-20.
SC-A sets much faster and it is recommended for very fast turn around situations.
XT-20 provides a longer pot life and can be customized from fairly fast setting to as long
as one hour after mixing.
Advantages:
• Faster Setting
• High early strength
• No loss of strength in time but progressive strength development
• Compensation of shrinkage through positive expansion
• Rapid drying
• Lower Efflorescence
• Denser Matrix
• Faster de-molding
SC-A and XT-20 are manufactured by Caltra NL, and distributed exclusively in North
America by CALTRA US Atlanta GA.