May 10, 2023

Concrete Production Ramps Up for Busiest Year

With this being the busiest year of construction, it is no surprise that, in 2023, crews will place the largest amount of concrete in all four years of construction. In total, the project requires 35,000 cubic yards of concrete. From August 2021 through December 2022, crews placed about 10,000 cubic yards. In 2023, crews will place 20,000 cubic yards. Concrete is placed daily at locations including the saddle dam grout cap, Chimney Hollow conduit thrust blocks, spillway, valve house foundation, tunnel lining and the Carter Lake interconnect.  

Concrete is made of coarse aggregates (gravel), fine aggregates (sand), fly ash, water and Portland cement, which is the most common cement. The only materials that are imported to the site are Portland cement and fly ash. Everything else is sourced from the on-site quarry. The quarry is first mapped to find the best hard granite, which is then blasted and hauled to the aggregate processing plant. Both the coarse and fine aggregate go through three crushers, separately, followed by a wash plant to remove fine dust. After the materials go through the aggregate processing plant, they are hauled to the concrete batch plant where they are weighed into batches and mixed.  

Concrete placement on the left abutment April 2023

Next, each batch is tested for air content and consistency. The air content is tested to look for microscopic air bubbles so that when the concrete freezes and thaws, it can expand and contract. The consistency is tested to make sure it’s not too thin or too thick, both of which could cause issues during placement. Once a batch passes the tests, it is ready for placement. The mix then goes into concrete trucks, like you’d see on city roads, and is transported to various areas for placement on site. 

Prior to the concrete being mixed, crews prep for placement by completing the form work, which includes rebar, forms and water stops. Inspectors must approve and sign off on the form work before any concrete is placed.  

When it’s time to place the concrete at its appropriate location on site, a concrete pump truck pumps it into place. It is vibrated to consolidate and densify the concrete into the form before a roller smooths the top to finish it. Depending on the outside temperature, it is then either cured with insulated blankets or with shade and cold water.  

Batching the concrete on site not only minimizes disturbances to the community, but it also keeps trucks off the road. Additionally, the Portland cement is more environmentally friendly due to a minimal amount of processing that results in a 10 percent reduction in the overall carbon footprint.