Combining flexible application with structural rigidity, Concrete Cloth is developing a niche in the resource sector.
Though the name may sound like a contradiction in terms, Concrete Cloth is a cement-impregnated fabric that sets up in any shape or configuration defined by the user without the use of molds, mixing or specialized equipment. The product was developed in the UK in 2007, and although it officially launches in the U.S. market this month, it's already been successfully applied in numerous projects in the gas, oil and mining sectors.
Concrete Cloth was initially developed to create emergency shelters following such disasters as earthquakes and tsunamis. "The material was being applied by emergency response teams as cement cladding to inflatable structures to create a rigid shelter in a short time period," says Richard Pilston, manager of new business development with the Performance Products Division of North American distributor Milliken and Company in Spartanburg, S.C. "That quickly led to interest in a number of other applications, such as using the material as a liner in civil erosion control applications and then expanded to other markets as it is approved in various jurisdictions for new applications."
The product is essentially a waterproof PVC membrane fused to a fiber mesh cloth impregnated with cement particles. A woven geotextile material on the product's surface allows for the cloth to be hydrated with whatever source is available, usually a water hose.
Pilston says the product is unique, competing against functionally similar materials such as formed and poured concrete, shotcrete (blown concrete), or fabric-formed concrete systems, in which concrete is injected into cloth forms.
The product is delivered to the user site in large rolls up to 3.6 feet in width, in thicknesses of 5, 8 or 13 mm, and then cut to shape and size. The longest roll comprised of the thinnest profile fabric stretches out to about 650 feet.
"The packaged rolls can be easily transported on a pallet," says Pilston. "They can also be ordered in lighter man-portable rolls weighing from 135 to 145 pounds. You can run a steel bar through it and then pull the fabric off the roll, cutting it with a standard razor knife or chop saw. If you're cutting with a power tool, you should wear a dust mask since the product will release some cement powder."
The material is then pinned, nailed or screwed into place, or supported by a wooden frame structure to provide its final shape.
"At that point you hydrate the material with any source of water," says Pilston. "We typically recommend an excess of water be applied, because you can't over-hydrate the product—you can use Concrete Cloth in the rain. One of the core elements of the intellectual property is the method by which we achieve the correct water-to-cement ratio. You can even apply water and then follow it up later with an additional application."
Once hydrated, the product begins to cure in about two hours. It achieves 80 percent strength after 24 hours, as it hardens into the shape specified by the user.
"The fabric also reinforces the concrete and reduces cracking in the final product, while using up to 95 percent less concrete than conventional methods, such as form construction and shotcrete," says Pilston.
In the gas, oil and mining sector, Concrete Cloth has been demonstrated in numerous projects. In underground mining applications, it's been used to quickly seal off unused mine tunnels to assist in airflow control. Maintenance crews build a frame in the open space and then fix the Concrete Cloth onto the frame and hydrate it. Within a day, the product acts as an effective air barrier.
Concrete Cloth has also been used underground to shore up tunnel walls and to prevent loose debris from falling.
"It's been used as a walkway material for mine workers, with sheets of cloth pinned to the ground underneath," says Pilston. "Research is also being conducted to see if a thicker material can withstand the traffic of light-duty equipment."
The cloth has been approved for mine use overseas, and in Ontario, Canada. In the U.S., it's currently passed Mine Safety and Health Administration fire testing and is awaiting approval for underground use.
Aboveground, the product has been used in a number of applications, from concrete maintenance and construction to a liner in pits, tailing ponds and spillways, often as secondary containment with the use of a geomembrane liner.
"In either gas, oil or mining environments, concrete takes a beating and may deteriorate due to exposure to a variety of different materials," says Pilston. "Concrete Cloth can provide a solution to a lot of maintenance issues. The cloth can be used to either repair a concrete surface, or it can be used as a sacrificial concrete layer to protect the infrastructure underneath."
In oil and gas, it's used as a pipe wrapping material. Applications include welded pipe joint protection, secondary containment, additional resistance to abrasion and sags, and chemical and corrosion protection. The product also provides extra weight to help pipes bed more effectively in wet soils where they might float. It's usable in marine applications because it can be hydrated
"We've successfully demonstrated its use as a temporary pipe repair material at a refinery in the western U.S.," says Pilston. "We've seen it applied to protect a conveyance line at a refinery between a stack and a storage unit. It's also been used as a protection layer for a variety of environmental impacts, particularly where the pipe runs aboveground and is accessible to people
A project planned for a western U.S. refinery will use Concrete Cloth to prevent erosion at a large settling pond.
"That refinery has a series of very large settling ponds," says Pilston. "The interesting thing about that area is that winds passing through the valleys can create waves as significant as a foot in height, which beat at the separation berms between the ponds and cause erosion. By placing concrete cloth at the boundaries of the wastewater ponds, we believe the erosion can be prevented."
For erosion prevention applications, surfaces should be relatively smooth with large chunks of rubble removed and large voids filled in to ensure an even application of the cloth.
Concrete Cloth can be applied in a wide range of temperatures, but is not recommended when nighttime temperatures will reach -25 degrees F. Structures should not be erected using the material when the ground underneath is frozen, since the soil will expand underneath the concrete structure when weather is warmer.
"Under durability testing we've performed, however, the concrete shows little loss of strength over more than 200 freeze-thaw cycles," says Pilston. "It appears to have a durability similar to traditionally applied concrete."
While Concrete Cloth is currently imported from European manufacturers, Milliken is establishing a manufacturing facility in Georgia, scheduled to open in early 2013.
"What's fascinating about working with this product is that it seems to drive people to devise project ideas in the sectors to which we introduce it," says Pilston. "Every time we demonstrate it in the gas, oil and mining sector, someone suggests an application we've never considered before."