Mechanical Concrete® Delivers Remarkable Strength, Savings and Simplicity
This environmentally compelling construction method creates a virtually indestructible engineered foundation for roads of all types. The key to this innovation is literally piling up around us: tires.
Mechanical Concrete is built with cylindrical tension bands created from used auto tires from which both sidewalls have been removed. These tire-derived cylinders are placed side-by-side on the ground covering the footprint of a road’s foundation, and nailed together into a grid. When appropriately sized stone aggregate is poured into the cylinders, the stones tightly lock together and behave as a solid, immovable mass: Mechanical Concrete. This construction method uses less stone, requires no compaction or curing, and is instantly ready to support construction loads.
Compared to the sophisticated techniques of modern road building, this technology seems almost primitively simple. Yet it’s proving a transformational success across the country.
Road projects using this green, sustainable construction technique have been completed or are under construction for 15 projects in five states – West Virginia, Ohio, Pennsylvania, Arizona and California. Customers include multiple public sector and commercial organizations.
An early adopter of this new technology is Laurita, Inc., a well-known northern West Virginia highway and heavy contractor and member of the American Road and Transportation Builders Association (ARTBA).
In 2010, Laurita constructed a 450-foot long coal haul road from the mouth of a coal mine to intersect with a West Virginia state highway. The new road replaced 36 inches of heavy asphalt road and base materials with an 8-inch Mechanical Concrete® base covered by a 10-inch reinforced concrete surface. It included two concrete abutment interfaces.
Workmen who had never used the technology quickly adapted to the disarmingly simple construction technique. The old rutted asphalt road was removed and the Mechanical Concrete base was completed in less than a week. The concrete pouring was completed in early December, during one of the coldest parts of the winter. The haul road went into service about 10 days later and now carries more than 200 coal trucks daily.
“This was our first and highly successful pilot of Mechanical Concrete,” said Tom Laurita, president of Laurita, Inc. “Coal haul roads take more wear and tear than almost any road. When a road product works in the mining industry it will work anywhere.”
He added, “We now have several other projects completed or underway using Mechanical Concrete supporting the coal industry.”
Another recently-completed Laurita project used a 9-inch Mechanical Concrete base for an access road at a Monongahela River coal barge loading facility in Morgantown, W.Va. The road was topped with an 8-inch crushed stoned wearing surface. In addition, the road incorporates two sections on either side of a commercial truck scale that are topped with concrete. Since June 20, the Mechanical Concrete road is successfully handling 300 trucks a day delivering coal to the river dock.
Because it’s virtually indestructible and economical, Mechanical Concrete can reduce low-volume road maintenance costs by 50 percent or more. Why? When vehicles roll along a road, about 30 percent of the vertical load is transmitted into the subsurface materials as horizontal (lateral) pressure. Over time, these lateral loads typically overcome the internal friction that holds the uncontained stone particles together in the subsurface of an ordinary road. Such a subsurface begins to spread apart, thus developing fissures, ruts and, finally, potholes. When a vehicle rolls over a Mechanical Concrete road surface, the tire-derived cylinders and the rigidly contained stone aggregate material efficiently absorb all lateral forces while remaining immobile.
“This is a strong, cost-effective, environmentally sensitive solution for our customer,” Laurita said. “Every day, this Mechanical Concrete road is proving to be a superb solution for this important commercial facility.”
Laurita, Inc., has a REAGCO license to construct with Mechanical Concrete in northern West Virginia and Southwestern Pennsylvania.
In a conventional road, rain also penetrates into the base materials, further reducing internal friction and stability. This causes surface cracks, potholes, ruts, shoulder failures and, potentially, washouts. Such base failures don’t occur with Mechanical Concrete because water doesn’t affect its strength or structural integrity. Because the Mechanical Concrete material is load bearing and porous, it works where conventional construction methods fail.
West Virginia was the first public sector entity to test Mechanical Concrete. In Doddridge County, residents along Morgan’s Run Road/Israel Fork had experienced three or four floods per year, which covered a state-owned roadway with 12 to 24 inches of flood water from an adjacent stream. In addition, the road is subject to regular traffic from timber trucks, oil and gas industry service vehicles, and occasionally by heavy construction vehicles.
In September 2006, the West Virginia Division of Highways installed a demonstration of Mechanical Concrete® consisting of 350 tire-derived cylinders placed adjacent to each other directly on the subgrade. They were filled with AASHTO #57 limestone and covered with a wearing topping of 6 inches of ¾-inch crusher-run limestone.
This 140-foot, one lane installation is now more than 5 years old. Mechanical Concrete was installed on the most flood-prone section of the road and has performed extraordinarily well. It has basically eliminated significant rutting wear and flood damage. No potholes or ditch damage erosion has occurred along the installation. The county road supervisor estimated that it reduced maintenance costs on that section of road by more than 50 percent.
Based on this successful pilot, West Virginia in October 2008 approved the use of Mechanical Concrete for road projects in the state.
Sundt Construction Projects
Sundt Construction is an Engineering News Record “Top 100” firm based in Tempe, Ariz. Sundt has now completed several road projects using Mechanical Concrete. Their initial project was built on a private ranch near the border in Arizona, which required building in high desert conditions that were subject to winter flooding.
Sundt has experimented with both a crushed stone surface and a natural resin spray-on topping that dries quickly to a hard and smooth road surface. It has produced Mechanical Concrete using a variety of aggregates and construction techniques. The company also has experimented with different soil conditions, placing the tire-derived cylinders directly on the soil and, where the subgrade was very soft, placing the cylinders on a woven separation fabric.
“Mechanical Concrete is an exciting breakthrough. It offers an environmentally responsible, sustainable and economical method for building rugged and cost-effective roads and other structures,” said Mike Hoover, senior vice president at Sundt. “Sundt looks forward to offering this transformational technology for other projects for public sector and commercial clients.”
Sundt has a REAGCO license to construct with Mechanical Concrete in California and Arizona.
Over several year cycles, pilot projects show that initial road construction costs using Mechanical Concrete are reduced by 30 to 50 percent compared with traditional road building techniques. Using Mechanical Concrete also reduces the volume (vertical height) of stone needed in the road cross-section to support truck traffic loads. This yields a lower cost to build and a solid base that delivers longer road life.
Lab tests show Mechanical Concrete to be at least twice as strong as necessary. The tires on a passenger car are usually inflated to 35 pounds of pressure per square inch, and impose roughly 12 pounds per square inch of lateral pressure on the Mechanical Concrete inner cylinder surface. Tractor-trailer trucks at maximum legal weight generate 100 pounds per square inch of vertical pressure. Each Mechanical Concrete cylinder is easily capable of sustaining 200 pounds per square inch of vertical pressure over it stone surface.
The natural gas exploration industry working in the Marcellus Shale fields of Pennsylvania, Ohio, New York and West Virginia places high-volume, heavy industrial loads on rural farm-to-market roads. After 18 months of failed road repairs in Wetzel County, West Virginia, Chesapeake Appalachia (a subsidiary of Chesapeake Energy) decided in August 2010 to try Mechanical Concrete®.
Chesapeake installed Mechanical Concrete on several sections of road, over a 2.5 mile stretch, and found the technology much easier to implement and significantly stronger than conventional roadwork.
“The foundation or the subgrade of the original road was soft — it was never constructed to handle the weight of the traffic that we were putting on it,” said Steven Mossor, former construction superintendent for Chesapeake Appalachia’s Central District of northern West Virginia and southwest Pennsylvania. “You could actually see the road surface rolling as trucks went by.”
He added, “We put Mechanical Concrete in our heaviest traveled area and it’s holding up well. It’s a lot easier and faster to build, offering much less interruption to the traffic flow.“
Since summer 2010, Chesapeake Energy also has been using Mechanical Concrete to repair public and private roads near the Ohio River in northern West Virginia.
The Reinforced Aggregates Company
The inventor of Mechanical Concrete is Samuel G. Bonasso, a civil engineer and former West Virginia Transportation Secretary. Bonasso received a U.S. patent for the technology in December 2008 and formed Reinforced Aggregates Company (REAGCO) to develop product applications and license Mechanical Concrete construction rights to construction firms, state and federal users and others who can profit from the technology.
“Engineers would never design something from scratch for road construction as strong and rugged as used auto tire-derived cylinders,” Bonasso said. “We are rescuing the tread portion of the tire after it has served its original purpose. By giving old tires a new life as tire-derived cylinders, we can use this waste material very inexpensively to make a virtually indestructible road base.”
Michael P. Jackson, former Deputy Secretary of the U.S. Department of Transportation and of the U.S. Department of Homeland Security, serves on the REAGCO board of advisors.
“I am confident that Mechanical Concrete will become a widely-adopted and routine method of building stronger, better roads – while also enabling a significantly reduced carbon footprint for the construction industry,” he said.
“In short, Mechanical Concrete offers transformational change to improve vital infrastructure.”
Further Information about Mechanical Concrete
Mechanical Concrete road bases deliver successful operating results with surface toppings of all types: crushed stone, asphalt, resin or concrete. Depending on sub-grade soil and surface load conditions, Mechanical Concrete may be placed directly on the soil subsurface or it may be used with geo-synthetics or fabric underlayment materials. The road segments of Sundt’s pilot projects, for example, were built in diverse subgrade conditions, which included the granular soils of Southeastern Arizona’s high desert, and powder-fine sand that had severely restricted constructing and maintaining conventional roads.
Mechanical Concrete® is built from scratch at the construction site. Unskilled construction laborers can transform stone aggregates into a new, solid, load-supporting building material much faster than conventional concrete construction materials, means and methods.
On average, 10 to 12 typical-size auto tires can create one cubic yard of Mechanical Concrete and 12,000 tire-derived-cylinders create one 12-foot-wide lane for one mile. Each year, the United States generates about 300 million waste auto tires – roughly one tire per person per year. Currently, about 89 percent of used scrap tires are recycled in some form, mostly for tire-derived fuel used for power generation. Still, some 128 million waste tires are stacked high in unhealthy and dangerous piles across the nation. Burying tire derived material is a preferred method by environmental agencies of using and disposing of waste tires. When a tire-derived cylinder is placed in the ground it is inert and poses no negative environmental threat. In the U.S. Environmental Protection Agency’s formal hierarchy of solid waste management, reuse of materials has greater environmental value than recycling the same product. In other words, reusing tires delivers greater environmental benefit than recycling tires.
Mechanical Concrete is field and lab tested. Six years of research and development has proven it to be the greenest and most economical method available for building a rugged, permeable and cost-effective road base. It can also be used to build foundations, walls, dams, revetments, fills, storm water retention and erosion control structures and other bearing type load supporting structures in architectural and civil engineering.
About REAGCO. Reinforced Aggregates Company (REAGCO), located in Morgantown, W.Va., has developed, patented (U.S. Patent 7,470,092 B2) and now licenses the Mechanical Concrete® technology. License applications and technical specifics for Mechanical Concrete® are described in more detail at www.reagco.com or visit REAGCO at the 10th International Low Volume Roads Conference sponsored by the Transportation Research Board on July 24-27 in Lake Buena Vista, Fla.