We have demolished two radioactively contaminated buildings down to their concrete slabs. One of the slabs has a concrete pit that is 26 ft (8 m) deep. The slabs have not been removed because the soil beneath the slabs is contaminated and we’re using the slabs as a cover to protect the spread of contamination in the soil until the soil remediation begins. We’d like to use shotcrete to temporarily (up to 5 years) fix the contamination on the slabs and the 5 ft (1.5 m) area surrounding them. The questions we have are: 1) Will shotcrete adhere to the concrete slabs and pit walls for up to 5 years without special preparations? (Portions of the radioactively contaminated concrete are painted and it is dirty from demolition activities); and 2) What is the minimum thickness of shotcrete needed to last for 5 years in this type of application? We do not want to use any wire or fabric mesh as it would require personnel to work in a radiologically controlled environment to install the material.
Shotcrete, like concrete, likely will not adhere to surfaces that are painted and dirty from the demolition activities. There should be no issue to the time durability. Shotcrete is pneumatically placed concrete and has great long-term durability characteristics if placed properly.Shotcrete has been installed in many adverse environments at a thickness of 2 in. (50 mm) with fibrous reinforcement and provided a long service life. Many irrigation districts line their canals with shotcrete and it has provided decades of great service in freeze-thaw exposures.
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