Backfilling With Lightweight Aggregate

Contractors enjoy practical experience of a different application with TXI's rotary-kiln lightweight aggregate.

In late summer 2001, Brent Vilhauer, vice president of operations at TRI DAL Utilities Limited, was awarded a project with underground tanks requiring pea gravel at the Dallas/Fort Worth International Airport. He needed an alternate granular bedding and backfill material that was cost effective and available in large quantities as an alternative to pea gravel and was impressed with what he learned about TXI's rotary-kiln lightweight aggregate. During the process of seeking engineering and budget approval for the use and purchase of the lightweight aggregate, two planes flew into the World Trade Center in New York City and all work on the DFW project was abruptly halted.

Fast forward to the following summer in Waxahachie where TRI DAL was a subcontractor working on the Cardinal Glass Manufacturing Plant, the leading manufacturer of residential coated glass. The facility consists of a 19,509.64-square-meter plant on a 121406.2-sq-meter site where workers add Lo?² coatings to raw glass used in residential windows. Vilhauer remembered TXI's rotary-kiln lightweight aggregate and ordered 382.28 cubic meter for use as embedment for utilities.

"This is an alternate product that's cost effective for trucking due to its weight and will eventually, in my opinion, take the place of pea gravel," said Vilhauer.

Other contractors on the job site (SME Electrical, TD Mechanical and Hidalgo Industries) noticed the aggregate's superior qualities in terms of reduced labor and material cost and inquired about using it in their own project applications. Product orders snowballed and more than 1758.48 cubic meter total was eventually used in approximately nine miles of underground electrical and mechanical work, including embedment for buried electrical cables, water and sewer lines; and backfill for grade beams. Of particular note, the aggregate was used to backfill large underground electrical duct banks, measuring 60.96 cm to 213.36 cm wide by 121.92 cm to 213.36 cm deep, that run electrical conduit under the building's foundation.

"TXI lightweight aggregate is a wonderful material," said Richard Kampen, project manager and supervisor with Design Structures LLC of Prairie du Sac, Wisconsin, which was the general contractor on the Cardinal Glass project. "The ease of use and the simple compaction effort of the aggregate made the installation process faster and thereby saved time and money."

Kampen explained that his work crew didn't need to bring in compacting equipment and was able to make backfill in 60.962-cm increments, instead of the standard 20.32-cm lifts that required compacting before placing additional layers. This dramatically reduced the amount to time required to make backfill.

Cost-Effective Choice

Kampen says an added bonus with lightweight aggregate was the cost savings on the price of the material compared to pea gravel, which has been historically used as a backfill and embedment material in Texas utility construction. Combine the purchase savings with the reduced labor and equipment costs and contractors familiar with lightweight aggregate are quick to mention that cost effectiveness is a big factor in their decision to use lightweight aggregate.

"Not only is the lightweight aggregate cheaper and easier to install, it's a quality product that performs as well or better for bedding and backfill than materials presently being used," said Larry Lyon, foreman with the MEP Projects Division of TD Industries. Lyon estimates that his company has used about 1529.11 cubic meter of the material in the past three years as backfill and embedment on various construction projects.

To date, engineers and superintendents on more than 20 utility construction projects in Texas have successfully used lightweight aggregate as an embedment, drain field and backfill material. Some of these completed projects include Lowe's Hardware Center in Marshall; John Eagle Toyota in Lewisville; Mims Creek Wastewater Plant in Fairfield; and Sonoma Basin Utilities in Ennis.

Produced from natural shale and clay, TXI rotary-kiln lightweight aggregate offers strength and long-term performance for a variety of construction uses. For more than 20 years, rotary-kiln lightweight aggregate has been used in the petrochemical industry as insulation under hot asphalt tanks to prevent the surrounding soil from moving due to temperature extremes.

Article provided by Pierpont Communications for TXI ESC division.