When the Ministry of Transportation of Ontario (MTO) issued new requirements for curing precast concrete in Spring 2009, Windsor-based Prestressed Systems Inc. (PSI) found a solution in Chamtech Systems' Rollcov-R retractable curing enclosure. The Montreal manufacturer collaborated with PSI in achieving regulatory compliance over the past year by placement of curing enclosures on five production beds for year-round fabrication of variously sized I-girders, box beams, and deck slab. In addition, two Rollcov-Rs have been installed for post-production curing, required by MTO for three to six days (depending on ambient temperatures) to ensure that product reaches its highest possible strength before storage outdoors.
MTO directives stress the need to pour and cover rapidly, as well as maintain a controlled and monitored environment to ensure that each precast component meets given standards. Mel C. Marshall, principal of Delta, B.C.-based Mel C. Marshall Industrial Consultants Inc., now represents Chamtech's Rollcov-R, having found it equal to achieving MTO-mandated practice and guidelines, including (but not limited to):
- Placing a moisture vapor barrier within six to 13 feet upon finishing the product
- Providing free air circulation around forms without forcing air directly onto the form
- Ensuring that no ice or snow is present on the forms before placement
- Accelerated curing via live steam, radiant or electric heat, or forced air within an enclosure able to effect even heat distribution
- Use of burlap or water spray throughout the accelerated curing cycle to protect the concrete surface from moisture loss; or, provision of 100 percent relative humidity throughout the curing enclosure. (The Chamtech Retractable curing enclosure protects concrete surfaces from moisture loss, alleviating the need to provide these measures.)
- Even heating of each member
- Continuation of accelerated curing until the specified transfer strength has been reached
- Control of ambient air temperature adjacent to concrete or formwork within the enclosure to ensure it does not vary by more than 14_F
- Application of protective measures, e.g., insulated tarps, when the temperature drops below 41_F, unless a housing and heating solution satisfies the above-referenced requirements
Efficient design and utilization of curing cells is imperative, particularly with energy costs rising so rapidly, says Marshall. MTO and others recognize the importance of designing effective curing enclosures Û a prime example being Chamtech's RollCov-R Û capable of ensuring against evaporation of moisture from concrete products, while maintaining a suitable ambient temperature.
Although most North American transportation agencies have not yet adopted similar curing standards, benefits of the Retractable enclosure extend beyond regulatory compliance, notes Chamtech Systems Project Manager Geordan Gay. When we first began supplying retractables to precast producers, we were soon advised that our systems were providing a quick ROI due to labor and energy savings, he recalls. One of our first customers claimed to have paid off an entire retractable in 14 months due to energy savings alone.
Echoing that statement, PSI Production Manager Chris Davidson calculated quick ROI due to labor savings. We have realized a significant savings from our loading crews, he asserts. They are no longer required to stay and wait until we finish pouring to tarp or come early to untarp.
Significant time savings constitute an added advantage of retractable curing enclosures at PSI. Davidson reports that crews are now able to continue working in rain and snow Û as we were not able to prior to installing these tarps Û and [since then] have not missed any production days due to weather. Besides protecting production schedules and precast from the elements, he observes that the appearance of product has improved slightly, as the enclosures help to maintain reasonable form temperatures.
Chamtech Systems emphasizes that its team of technical representatives aims to determine the most economical and effective solution for a producer by assessing the demands of a particular operation and environment. PSI Project Manager Randy Primeau affirms that Chamtech worked closely with us during concept and design phases and, during installation, provided knowledgeable, hands-on site assistance. Adds Prestressed Group CEO Loris Collavino, The quality of the covered system, the support from Chamtech Systems staff, and the ease of use these systems provide have made them a tremendous asset to our operations.
PSI is a member of the Precast/Prestressed Concrete Institute, Central Chapter, and the Canadian Precast/Prestressed Concrete Institute (CPCI), which also counts Chamtech among its members.
Information and testimonials were provided by Chamtech Systems, which will exhibit (Booth #618) at the PCI Annual Convention & National Bridge Conference in Washington, D.C., May 29 through June 1. Û www.chamtechsystems.com