Nuclear Station Lightweight Fill

cellular concrete for lightweight fill over underlying utilitiesChallenge:

Upgrade work to a nuclear plant in New England required installation of lightweight fill.  As part of flood damage prevention upgrades, load reduction was needed over three buried emergency cooling pipes.  The work area was located immediately adjacent to a reactor building, so all staff had to pass rigorous background checks, and any materials and vehicles coming onsite had to go through a thorough inspection.

Limits:

The primary requirement on the job was achieving 300PSF of load reduction in the 4 feet of cover over the pipes.  Additionally, the fill material had to tolerate near immediate asphalt overlay followed by heavy rigging equipment traffic.  As part of the flood control upgrade measures, the lightweight fill material had to tolerate construction of a temporary Hesco wall dam on top of the mass, without consolidation of the lightweight fill.

The Solution:

Given the need to be load reducing, but tolerable of heavy loads soon after placement, and a desire to avoid as much buoyancy as possible, cellular concrete was the most appropriate lightweight fill material.  

Geo grid was cast into the adjacent concrete, and then embedded into the cellular concrete to increase tensile strength of the mass.  The geogrid was cast into the adjacent flowable fill in order to ballast the buoyancy of the cellular concrete.

Result:

CJGeo placed 90 cubic yards of 30PCF wet cast density cellular concrete, with a dry density of approximately 26PCF.  CJGeo worked with multiple parties to design a slurry mix tolerable of long transport times to the facility and up to hour long waits to pass through security screening.

The 30PCF cellular concrete provided a bearing capacity exceeding 15,000PSF, ensuring adequate bearing capacity in case the flood protection measures needed to be implemented.  Due to the need to traverse the placement with equipment, test slabs were poured for load testing to assess loading tolerance without damaging the in-place mass.