Heidelberg Materials North America has detailed the concrete behind the hardest piece of Houston Methodist’s $1.4 billion Centennial Tower: a post-tensioned transfer girder 27 feet deep that cantilevers 53 feet over the ambulance drive. It took about 1,800 cubic yards of 8,000-psi concrete placed as a single mass pour, and the supplier is pitching it as a low-carbon mix without saying how low.
Heidelberg published the project write-up Oct. 14. The 26-story tower in the Texas Medical Center tops 1 million square feet and holds nearly 400 beds. Vaughn Construction is the general contractor, Walter P Moore is structural engineer and Page, now part of Stantec, is the architect. Keystone Structural Concrete placed the superstructure concrete, all of it supplied by Heidelberg.
Why the transfer girder needed mass concrete
The girder sits on a mechanical floor above grade so columns don’t land in the ambulance drive below. To balance the 53-foot cantilever and limit uplift, the design adds a 68-foot backspan. About 300 post-tensioning tendons run through it.
That geometry pushed the pour into mass concrete territory. A member this thick generates heat at its core faster than the surfaces can shed it, and a big temperature differential cracks the section. So the team specified a low heat of hydration and treated the cantilever and backspan as one mass placement. Keystone built mock-ups before construction to test the placement plan.
The low-carbon concrete claim
The mix was Heidelberg’s EvoBuild Silver at 8,000 psi. The company says it has lower embodied carbon than a conventional alternative. It doesn’t give a percentage, a baseline mix, a cement type or a slag or fly ash content, and it doesn’t cite a product EPD in the write-up.
That’s a gap worth noticing. Low heat and low carbon often come from the same place, since replacing portland cement with supplementary materials cuts both. But 8,000 psi with tight thermal limits is a demanding spec, and without the replacement rate or an EPD number, an owner can’t compare it with a competing mix. Industry averages exist for that kind of check. NRMCA’s updated industry-wide EPD covers 120 mixes, and slag supply in the region is growing as new mills open.
What it means for hospital builders
Hospitals are where this detail keeps showing up. Ambulance bays, imaging suites and mechanical floors all push designers toward long transfers that leave structure off the ground floor, and high-strength mass pours come with them. Contractors bidding those jobs should get thermal control plans, mock-up requirements and the supplier’s carbon number into the submittal, not the marketing.
The tower’s phased opening is set to start in 2027, five years after construction began. If Heidelberg publishes the EPD for this mix, it’ll be one of the few public data points on low-carbon concrete at 8,000 psi in a mass pour.