The American Concrete Institute (ACI) has released a paper called Delayed Ettringite Formation in Concrete Containing Limestone Filler.
The study investigated the influence of cement and limestone filler (LF) particle size on self-consolidating concrete expansion due to delayed ettringite formation.
ACI says: “LF was used to replace 15% of the cement. All concrete mixtures had 5% silica fume and a water-cement ratio (w/c) of 0.34. The concrete mixtures were steam-cured at a maximum temperature of 55, 70, and 82°C (131, 158, and 180°F).”
Results showed that LF increases the 16-hour compressive strength when concrete was steam-cured at 55°C (131°F). In addition, LF did not have a significant adverse effect on the later-age (28- to 300-day) compressive strength, regardless of steam-curing temperature. The permeability of concrete at 28 and 300 days was reduced in the presence of LF.
According to ACI: “Steam-cured concrete mixtures at 82°C (180°F) expanded and developed microcracks after 300 days. This expansion and cracking caused a significant reduction in the freezing-and-thawing resistance compared to steam-cured concrete mixtures at 55°C (131°F).”
The report reveals concrete mixtures made with LF and steam-cured at 70 and 82°C (158 and 180°F) showed lower expansion due to delayed ettringite formation after 300 days compared to concrete mixtures made without LF. This was caused by a reduction in cement content and in concrete permeability when LF was used.
