Inside the mass of concrete, some of it up to 14 feet thick, is about 1.25 miles of conduit, 100 tons of rebar and more than 100 mounting plates, supports and boxes that must be exactly placed and embedded. Combined, almost 50% of the construction cost of a proton therapy project is reflected in the cost of concrete and everything inside it. Below, we provide key best practices for concrete quality control in proton therapy construction and how it directly impacts project success.
Quality in Planning
Due to the significant investment in this early phase of the project, Gilbane has learned that developing comprehensive and detailed quality control plans is vital for project success and must be established early for all aspects of the project. Quality control must be closely monitored for the following key items:
- Identifying the specification of the concrete aggregate mix
- Planning of the mass concrete pour sequences
- Forming and placing of the concrete itself
- Coordinating of the embedded materials
The specification of the aggregate mix typically references a necessary dry density value to meet radiation shielding requirements. As important as the aggregate mix is, contractors must be equally concerned with additional components beyond the concrete basics, including:
- Wet density for pumping
- Controlling the positioning of all embedded items to ensure the position is maintained during concrete placement
- Off-temping characteristics to control temperatures of the mix for appropriate curing
Quality in Coordination
Once the details of the mix have been confirmed and ordered, it is essential to coordinate the accurate placement of forms, rebar, conduits and embeds all in a manner to ensure they fit and stay in place during concrete pours. During construction of a typical single room vault, a total of about 2,500 cubic yards of concrete is delivered to the job on 350 trucks. The delivery and planning of this massive amount of concrete is extremely complex and begins in preconstruction.
There is a limited amount of concrete that can be placed in one day. Therefore, it is essential to develop a detailed phasing plan and schedule for all concrete pours to understand key aspects of this process, including:
- Where the embedded conduits begin and end at each point
- How rebar is placed across each pour
- How much time is needed for interim curing of already-placed concrete
The conduits that need to be embedded often have constraints on bend radius, elevation angles and maximum lengths that must be adhered to because the vendor equipment interconnecting cables may have length limitations. Coordinating these complex elements in a relatively small amount of time and space takes extremely close coordination and planning.
Quality in Execution
Finally, quality control in the execution phase is critical to ensure the delivery of a state-of-the-art proton therapy center for exceptional patient care. There are several key stages of a concrete pour that are required to ensure the integrity of the structure and shield from radiation, including:
- Logistical planning to bring in over 350 cement delivery trucks
- Maintaining appropriate concrete mix temperatures
- Ensuring rebar and supports are in place to affix necessary conduits
This complex work culminates with equipment delivery, rigging of the equipment into the rooms and installation of the miles of interconnecting cabling in all the conduit.
Learn more about Gilbane’s approach to proton therapy construction and view success stories here.
