THE JOB
A utility contractor installing 500LF of 48″ HDPE reline pipe through a 63″ CMP culvert required annular space grouting done at very low installation pressure yet able to ensure complete filling of the washouts outside of the CMP. This HDPE reline annular space grouting project is located in Baltimore, Maryland.
THE CHALLENGE
Due to traffic control limitations, only one end of the pipe was accessible for grouting. Therefore, all grout installation was done with up to 200LF of pumping to get to the bulkhead and then up to 500 feet of travel through the annulus via sacrificial grout tubes. Bulkhead leaks usually result from extensive voids outside of the host pipe. This pipe’s invert corrosion posed unique challenges for containing the annular space grout. CJGeo proposed cellular concrete for the annular space grouting. Cellular concrete is highly flowable. High flowability ensures low installation pressure, reduces flotation of lightweight carrier pipes, and ensures complete void filling outside of the host pipe. Using cellular concrete for annular space grouting was specified by the HDPE slip lining pipe manufacturer.
THE SOLUTION
CJGeo successfully performed this HDPE reline annular space grouting project over two days, in two lifts. Multiple lifts reduce the heat of hydration and carrier buoyancy. The cellular concrete-filled all of the voids outside of the host pipe. The peak pressure at the pump did not exceed 15PSI throughout the project. Therefore, the project was successfully completed without floating, deflecting, or damaging the HDPE slip line pipe.
CJGeo placed 30PCF wet cast density CJFill-Ultra Lightweight, with a 125psi compressive strength for this project. With a 24 hour penetration exceeding 50psi, 30PCF cellular concrete reduces buoyancy with its low unit weight, provides adequate strength, and rapid stability.
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