Internally Cured Concrete Steals the Show in Denver
Denver Water Department’s three successful water tank projects drive an ongoing demand for internally cured concrete across multiple districts.
Since 2010, Denver Water Department has been spearheading the construction of enormous water tanks at three different sites within its district. In Lone Tree, the region’s pump station and water tank play an integral part in supplying water to the Southgate Water District, which supplies the City of Lone Tree and surrounding areas. There, the department built a new, 10-million-gallon underground water tank that is now providing a reliable water supply and also meeting fire response needs.
In Ashland, Denver Water’s $40 million project involved replacing two 20-million gallon tanks that previously sat on the 120-year-old site. Click here to view a related video. And in Highlands, the department built a new, 7-million-gallon circular post-tensioned concrete water storage tank, installed yard piping, and made other site improvements.
All of these successful projects had at least one thing in common: they all utilized internal curing of concrete in one way or another. Often referred to as “curing concrete from the inside out,” and known for its ability to reduce cracking and shrinkage, internal curing is a practical way of supplying additional curing water throughout the concrete mixture. This is done by using water absorbed in expanded shale, clay, or slate (ESCS) lightweight aggregate, which replaces some of the conventional aggregate in the mixture.
According to ASTM C1761, Standard Specification for Lightweight Aggregate for Internal Curing of Concrete, internal curing provides an additional source of water to sustain hydration and substantially reduce the early-age autogenous shrinkage and self-desiccation that can be significant contributors to early-age cracking.
Clint Chapman, Technical Sales Manager for Trinity Lightweight, said that over the last six years his firm supplied the lightweight aggregate used for internal curing of the concrete used to build the Long Tree and Highlands tanks. It also supplied the lightweight aggregate for the Ashland tank, for which internally cured concrete was used for the floor and the roof slab.
Chapman said the only challenging aspect of these three projects was getting everyone onboard with the idea that internal curing was the best option for the construction of the huge water tanks.
“Internally cured concrete ‘acts’ just like ordinary concrete, but because it is relatively new, and uses an additional ingredient in the concrete mixture, people tend to be apprehensive about using it,” said Chapman, whose firm used an educational process and a test site to prove the value of internal curing. “Once we broke through that barrier, the projects were pretty straightforward.”
According to Chapman, Denver Water is pleased with the project results. “Denver Water is pushing to use this process across all of its water tanks now,” said Chapman, “due to the dramatic decrease in cracking and leakage that they’ve seen on the tanks that are already done. It’s worked out very well.”