Virginia Polyurethane Grouting

Virginia Tech

The Job

This Virginia polyurethane grouting project is located in Blacksburg, Virginia, at Virginia Tech. The work was done to support continued occupancy of the structure, after voids as deep as two feet were located below the floor slab.

The Challenge

A small area of the ground floor slab on grade settled, primarily adjacent to the basement, which is only under about 20% of the building footprint. The basement contains mechanical equipment, and ties to a large crawlspace used as a ventilation duct.

Upon initial discovery, the university’s on-call geotechnical and building envelope consultant performed exploratory drilling to determine the extent of voids. Several auger bores for exploration of the backfill material identified poor control during installation as the most probable cause of settlement.

The Solution

CJGeo was the most responsive bidder on the owner’s solicitation, which called for filling the voids below the floor with CJGrout 20SDB geotechnical polyurethane. 20SDB is specifically formulated for maximum expansion, high mobility, and very low exotherm.

One particular challenge was the amount of glass gravity drain piping below the floor. Because much of the building is lab space, when it was built, the most chemical-tolerant pipe available was glass. So, it was very important that the polyurethane grouting work not damage the relatively fragile pipes.

CJGeo timed its work around spring break to avoid any disruption to classes, research, and offices. The work took six days onsite, and a total of just under 10,000 pounds of CJGrout 20SDB.

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