Turner Construction and AECOM are lowering costs without compromising safety as they build a new home for the Los Angeles Rams and Los Angeles Chargers. One way is by using special aggregate to build suspended slabs in the $2.6-billion stadium. (For more about elevated slabs, click here.)
The slabs are cast-in-place panels made with HydroLite, Trinity Concrete's brand of expanded clay aggregate. Expanded clay aggregate was developed by Stephen Hayde, "the father of the lightweight concrete industry," in 1918. It absorbs water, which stays in the aggregate's pores until the concrete sets. As the mixing water begins to be used up and evaporate, the absorbed water is drawn out of the pores and continues the hydration process. This internal curing adds strength and reduces shrinkage cracking.
“The material sucks that water in and stays wet, so that's where the name Hydrolite comes from," says Trinity Lightweight's Charles Kersic. "We soak the material at our plant during the processing time and keep it wet in the stockpile.” This is important because ready-mix plants in California don't have room to store material long enough to prewet it sufficiently.
Expanded clay lightweight aggregate is more expensive than normal-weight concrete because of processing costs, but saves money on the structure by reducing dead loads. Lightweight concrete placed at 120 pounds per cubic inch has an equilibrium density -- the density reached by structural lightweight concrete after exposure in a relative humidity -- of 110 compared to 145 for normal-weight concrete. Expanded Shale, Clay, and Slate Institute members sell more than 6 million cubic yards per year.
CalPortland is at the L.A. Stadium with a portable plant producing the estimated 40,000 cubic yards of lightweight concrete the suspended slabs are expected to consume. The stadium is scheduled to host Super Bowl LVI in February 2022, College Football Playoff National Championship in January 2023, and the 2028 Summer Olympics opening ceremony.