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Prince George project pours cost-effective concrete

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by Warren Frey last update:Sep 15, 2006

Innovative use of self-compacting concrete promises savings in time and labour costs on a major construction project underway in Prince George, British Columbia.

Northern Sports Centre using self-compacting concrete to save money and time

VANCOUVER

Innovative use of self-compacting concrete promises savings in time and labour costs on a major construction project underway in Prince George, British Columbia.

The material was chosen over conventional concrete by Western Industrial Contractors Ltd., (WIC), the general contractor working on the $30.5 million Charles Jago Northern Sports Centre at the University of Northern British Columbia (UNBC).

The self-compacting concrete mix is being used in the construction of 42 load-bearing pillars, each one 40 feet high that support the centre’s curved roof structure. Seventeen of the columns feature cantilevered arms to support interior running tracks.

Experience with the first 15 pillars erected indicates using the self-compacting concrete is about four times faster than a conventional mix, says Keith Hillen, Western Industrial’s site superintendent. And the concrete reaches its designed compressive strength in seven days compared with the usual 28 days for conventional concrete. The speed of pour and elimination of vibration compacting contributes further to labour savings, he adds.

The self-compacting concrete is poured from a conventional pump truck, supplied by Inland Concrete Ltd., in Prince George. The mix is less conventional being more fluid in character and pumped from the bottom up. A 20 foot column section can be poured in less than 15 minutes. In fact, points out Hillen, the pump truck needs to be idled down during concrete delivery.

Another different factor on the UNBC job is that wooden formwork is employed. The clamped, rectangular forms are made of plywood and 4x4 fir and have worked well, withstanding pressures and sustaining less wear and tear, continues Hillen. “The concrete finish is smooth like glass with no remedial work needed later on,” he adds. And another advantage:

“Crews love working with it because it’s easier.

The self-compacting concrete costs 15-20 per cent more than conventional concrete and the formwork is relatively labour intensive, concedes Hillen. But that’s offset quickly by the time savings and other advantages of the self-compacting mix, he notes.

Hillen says he believes this is the first time in Canada self-compacting concrete has been used in this type of application. The material has been used successfully in the United States and Europe.

It was Hillen, a 15-year employee, who suggested WIC use self-compacting concrete on the sports centre job. “I stuck my neck on the line and put the bug in their ear,” he recalls. Hillen was aware of the concept and researched the process and checked it out on the Internet.

WIC sent local sand, aggregate and cement powder for testing to Lehigh Cement Company in Seattle. After passing muster there, WIC erected a small test column using the material at UNBC.

Since then, it’s been a case of so far, so good, says Hillen. Indeed, the compressive strengths achieved in the self-compacting concrete in the field has exceeded the test design results in the lab. WIC continues a rigorous testing process. “We’re very precise in our testing,” he reports.

The Northern Sports Centre is on a very tight construction schedule, point out Hillen. Anything that can save time without compromising the integrity of the job is a welcome benefit to the contractor.

The sports centre is slated for substantial completion in August 2007.

The 320 foot long, 210 foot wide structure will include two indoor soccer fields; a three court gymnasium with seating for 2,000 spectators; a fitness centre; training and preparation facilities; offices and administration spaces. The centre will be connected with UNBC’s cross-country skiing and biathlon trail network adjacent to the hilltop campus.

last update:Sep 15, 2006

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