PPC cement, coarse aggregate ( mixture of 3/4 th inch & 1/2 inch downgraded stone chips), fine aggregate (coarse sand), and admixture (MasterPolyheed) is used for this construction.
Fresh density is kept above 2.4 gm per cc. The hardened density requirement is above 2.35 gm per cc.
Ice is being used to decrease the mixing water temperature. (To avoid hairline crack in the future)
Key concern is to avoid radiation leakage.
The rooms are being constructed in the basement with wall thickness of 5 to 8 feet and slab thickness of 4 to 8.5 feet. Rooms will be used for Oncology treatment and/or Tomotherapy.
make sure the concrete is mixed and poured properly, then vibrated (to get the bubbles out). During pouring, have some samples poured into small plastic containers for laboratory analysis for elemental composition and mass density. Of course, the shielding survey measurements will be very important ...
In addition to Dr Newhauser's comments, here are some other considerations:
Use high density coarse aggregates, for eg, granite in place of limestone
High workability of concrete and sufficiently spaced reinforcement
Monitoring and controlling heat of hydration during casting and subsequently. Cement replacement materials like fly ash and silica fume are good choices as they not only decrease the rate of hydration, but have filler properties resulting in fewer pores in the matrix.
Sufficient shrinkage reinforcement
Substantial and sustained curing
Hi,
I cannot stress the importance of vibration enough! We had a contractor who didn't, this resulted in visible honeycombing and a huge mess to fix...
Additional to these recommendations, you must consider that this is a massive pour. ACI has these documents:
ACI-207-2.R-95 Effect of Restraint, Volume Change, and Reinforcement on Cracking of Massive Concrete
ACI-207.1R-05-2012-Guide to Mass Concrete
ACI 349_06_Code Requirements for Nuclear Safety-related Concrete Structures
It is very important to maintain the maximum temperature and the differential of temperature (inside-and-surface) inside the range recommended by ACI. Ice will help but additionally you may need insulate the pour and/or circulate cold water to drop the inside temperature.
Texas DOT has a public software to estimate the temperature of massive concrete pours:
http://www.txdot.gov/inside-txdot/division/information-technology/engineering-software.external.html
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