ASK SAM
Sam Bonasso, the civil engineer and inventor of Mechanical Concrete® takes questions from people in the construction world including owners, engineers and architects, and everyone on the contractor’s team. He also shares what’s current in the world of Mechanical Concrete®.
If you’ve got a question you’d like to Ask Sam, contact us today, and visit us here for the answer!
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Construction
How many tire-derived-cylinders does it take to build a road?
Approximately 12,000 tire-derived-cylinders derived cylinders cover one 12 foot wide lane one mile long. This assumes a standard 28 inch diameter tire-derived-cylinder 8 inches wide. About 8000 cover an acre of ground.
What kind of sub-base soils have been successfully used to construct Mechanical Concrete® road bases?
Mechanical Concrete® road bases have been on constructed on soft Appalachian clays and soft southwest US desert sands and a wide range of soils in between. On the soft clay and sand, woven separation fabric was laid and then the tire-derived-cylinders were placed and filled. Our research shows that confining the aggregate in the tire-derived-cylinders actually improves its load bearing capacity by double or more.
What is the preferred stone gradation?
AASHTO # 57 is the recommended gradation for most uses. Other larger, same-size stone gradations, i.e. AASHTO #3, may be used depending on the application
How much stone is consumed by Mechanical Concrete®?
Tire-derived-cylinders widths vary. For an 8 inch wide cylinder a 12 foot wide lane mile uses approximately 2300 tons. That’s approximately 290 tons per inch of thickness at a stone density of 110 lbs. /cf.
Why should a builder consider using Mechanical Concrete®?
Besides being green, which is a major concern, and being economical, Mechanical Concrete® is faster to build and it’s easier and safer to use than conventional concrete. It requires no forms or special finishing. It solidifies instantly to support loads, so it requires no curing time. It requires no reinforcing steel to perform its function. It uses less energy and smaller equipment. Finally it is considerably less expensive than conventional concrete. Mechanical Concrete® is Faster, Easier and More Economical.
Engineering
Just what is Mechanical Concrete®?
Mechanical Concrete® is a way of binding crushed stone aggregates together into a load bearing cellular building unit. The Mechanical Concrete® unit can support compressive loads and resist lateral soil pressure. It is basically a compressive material. Mechanical Concrete® confines the stone within a Mechanical Cement®, stay-in-place, cylinder. This tire-derived-cylinder performs functions similar to the cement / water mixture, the rebar and the formwork in hydraulic cement concrete. It actually improves the load bearing capacity of the aggregate material be it sand, stone or sandy clay.
What is a Mechanical Cement® cylinder?
A Mechanical Cement® cylinder is a thin-walled cylinder. It can be designed and made from any suitable material of adequate size and tensile strength to resist the lateral pressure generated when the crushed stone is placed under load. This lateral pressure can be calculated using established engineering formulae. It is the tensile strength of the Mechanical Cement® cylinder that generally defines the overall strength of Mechanical Concrete® and not the crushed stone. A Mechanical Cement® thin-walled, cylinder can be made of single material or of composite materials. For example, the cylinder can be made of steel or plastic. The preferred cylinder is made from a recycled auto or truck tire with both sidewalls removed. The tire-tread cylinder is no longer a tire but through remanufacturing becomes a tire-derived-cylinder, TDC.
What is the load capacity of a Mechanical Concrete® cell?
The tire-derived-cylinders are used at maximum operating pressures of approximately 45psi plus a design factor. When used at low pressures as in Mechanical Concrete®, i.e. around 12 psi for an AASHTO Truck Wheel Loading, it can be used effectively and economically in nearly all construction, on-road or off-road applications for a maximum wheel loading of 50,000lbs. The results of Mechanical Concrete® 50,000 lbs. column lab load tests are available on this website.
This basically means that the Mechanical Concrete® process improves the load carrying capacity of the earthen materials that make up a road. In fact it more than triples the usual maximum load carrying capacity of sandy, granular, and graded stone materials.
Have any public roads agencies approved Mechanical Concrete® for use?
Yes, the West Virginia Division of Highways, Materials Division has approved Mechanical Concrete®. A copy of the approval letter is available on this website.
How are the low-cost economies of Mechanical Concrete® achieved?
First, Mechanical Concrete® uses less general labor and less skilled labor. Next, it consumes less energy in its construction process since it can use smaller equipment. Then, it requires no compaction, vibration, forms or rebar. Also, it reuses a ready-made cylinder that is a low cost, combination stay-in-place form and reinforcing element. It uses the compressive load bearing capacity of low-cost stone aggregates or other recycled or earthen aggregate materials. It is simple to understand and use so it improves construction worker productivity. Because of these characteristics Mechanical Concrete® simplifies, speeds-up and facilitates the construction process.
What kind of savings can be expected from using Mechanical Concrete®?
As with most construction the answer is, ‘It depends on the particular application.’ When compared to the cost of retaining walls, bearing walls and foundations, roads and site stabilization made of conventional concrete or compacted stone; Mechanical Concrete® can deliver a minimum 25% savings. In many cases this savings can be as high as 50%. In road construction the savings can be 25 to 30% or more depending on the aggregate used.
What kind of real dollars can Mechanical Concrete® deliver in the way of savings?
On our first project in Morgantown, WV, (The Greater Pittsburgh Market); Mechanical Concrete® showed it could produce the wall for a mechanically stabilized earth, (MSE) retaining wall system for about $12 per square foot of wall area. Compare this with a $22 to $30 per square foot cost for segmented block wall in the same application. This MSE wall experience translates into a cost for Mechanical Concrete® used in a foundation application in the same location of $90 per cubic yard in place ready to support loads. Compare this to $150 to $200+ per cubic yard for conventional concrete foundations.
When compared to gabion wall retaining wall systems Mechanical Concrete® using truck tires reduces construction costs by over 50%.
Sustainability
Why do recycled vehicle tires work as a Mechanical Cement® cylinder?
Tires treads which interface with the roadway have a composite structure of woven steel belts and polyester chord reinforcing, all of which is embedded in a rubber matrix. Auto tires are designed to withstand road hazards and operate at a maximum air pressure of approximately 44 psi. And on top of this manufactured products usually have a design factor for an ultimate stress. Because of these engineering material characteristics the tire-tread cylinder has the necessary circumferential tensile strength to support the lateral pressures generated in the aggregate material by civil engineering dead and live loads.
How green is Mechanical Concrete®?
Mechanical Concrete® is one of the first green construction products to be highly durable, technically appropriate and economical as well as green and sustainable. This is because it actually reuses a manufactured product. Its use reduces greenhouse gases, reduces construction site energy consumption, reuses manufactured materials, improves air and water quality, reduces cement use with a pound for pound reduction in greenhouse gases, and generates no construction material single-use waste. Further green information may be requested at sam@reagco.com.
Mechanical Concrete® as with most new technology can be expected to achieve even greater efficiencies as it continues to develop.
How many scrap tires are generated annually and how does this relate to the conventional concrete market?
The United States generates approximately one tire for each person every year. That’s about 300 million scrap tires annually. Currently 80 to 90% of these scrap tires are recycled by grinding them up and placing them in landfills and about half of these are burned as fuel for power and other uses and thus generating greenhouse gases.
On average 10 to 12 typical size auto tires can create one cubic yard of Mechanical Concrete®. This means that 300 million tires could generate between 25 and 30 million cubic yards of Mechanical Concrete® or about 6% of the conventional concrete market. Tire tread cylinders will be used as Mechanical Cement® primarily in the heavy and highway construction market. Other Mechanical Cement® cylinder materials products will serve the commercial and residential construction market.
For example, 9 tire-derived-cylinders filled with about one ton of AASHTO #57 limestone generates one cubic yard of Mechanical Concrete®. Compared to hydraulic cement concrete this eliminates 6 bags (564lbs) of cement, about 45 gallons of water, and 3 / 4 ton of sand and all the mixing energy and forming costs.
Business Issues
Aren’t you afraid someone will copy Mechanical Concrete®?
As with any technology, if it works and saves money, someone is likely to try to copy it or knock it off. REAGCO has a US patent and a lot of unique know-how. This tells any potential copiers that they could be in federal court at some future date if they attempt to copy the technology.
We also have registered US trademarks for Mechanical Concrete® and Mechanical Cement®. This means we have a brand name that is ours and no one can steal or copy it without serious legal and financial consequences.
But REAGCO also has something no one else we are engineers and construction people. That means we have know-how that we have developed and continue to develop. Every construction project is a challenging environment. It requires that work be performed in a proper sequence and timely manner and that work be done safely. REAGCO has created the specifications and basic details for the proper applications and use of Mechanical Concrete® and these are all copyrighted documents. This offers additional protection from would-be copiers.
Finally, and this is very important, it will be much easier and less expensive for a would-be copier to work within REAGCO‘s system than to reinvent our knowledge and experience. It will be more economical and beneficial for anyone to purchase their Mechanical Cement® cylinders from one of our dealers than to do it themselves or acquire a project license and the technical support it offers. There are also numerous other reasons why a copier would have a much tougher job doing it himself than just working with REAGCO.
How big is the market for Mechanical Concrete®?
The annual conventional concrete market according to 2005 Concrete Construction Magazine is estimated at 484 million cubic yards, annually, approximately $110 billion. The concrete market is distributed as follows:
• Residential 199M cubic yards
• Pavement 145M cubic yards
• Commercial 32M cubic yards
• Other 108M cubic yards
Currently with scrap tires and other types of Mechanical Cement® cylinders, Mechanical Concrete® can economically compete and pursue applications in about 25% of the conventional concrete market. So our target is a $30B market.
The US road building and road maintenance market is even bigger. So there are a lot of economic opportunities for this product and for the people who supply and construct with it.
What is the REAGCO business model for selling Mechanical Concrete®?
Mechanical Concrete® is sold through a network of licensed regional Mechanical Cement® dealers. It also offers construction project Mechanical Concrete® patent licenses to highway and heavy contractors and project owners. This business model generally conforms with the used tire market and can efficiently serve the heavy and highway construction market segment and the commercial and residential construction market. REAGCO supports its dealers with R & D, national and regional marketing and technical know-how from the royalties it receives in technology license fees from its dealers and contractors.
The commercial and residential construction market may be served in the future through Mechanical Cement® products sold by retail construction supply organizations.
Which businesses are best suited to become local Mechanical Cement® dealers?
Regional tire companies who want to expand their business model are well suited. Most of these businesses now work with the construction industry. Each outlet can become a Mechanical Cement® dealer and serve the local community. Next tire recyclers can become dealers who want to go beyond grind-up tire products to a more profitable, remanufactured, tire derived product.
What kind of investment does it take to become a dealer?
The dealer package includes tire cylinder making equipment, business plan and an accounting and a marketing processes. If the interested dealer owns an existing building and storage yard facility the dealership investment is approximately $50,000 per community of 50 to 100 thousand people plus annual minimums. The cost of dealerships in larger cities or regions is based on the potential of the applicant to service the market and produce the products.
Projects
How are the demonstration projects working out?
Our three early West Virginia demonstration projects, a unpaved test road way, a gas well service pad and a 190 foot MSE, mechanically stabilized earth, retaining wall supporting a commercial office, hill side, parking lot. These demonstration projects are over 5 year’s old and exceeding all expectations for durability to loadings and weather conditions. This means they are functioning better than predicted and have had no unexpected behavior. The retaining wall is stable and performing to eliminate active soil pressure. The gas well service pad is provided a solid ‘parking lot’ type foundation for well service vehicles.
The roadway has been the most promising. It has experienced 2 or 3 floods each year and has retained its stability and not lost its Mechanical Concrete® base. This means that the flood waters have not easily displaced the cylinders and the base stone. Repair after flooding has been limited to resurfacing with a wearing course. Further deterioration of the roadway base due to flooding has basically been eliminated.
In 2009, 1400 feet length of 12 foot wide road way was constructed on a ranch in the high desert of SE Arizona. This road is also subject to seasonal flooding. Road placement productivity rates of 200 linear feet per hour were achieved with two men and one 3 cubic yard front end loader. This means that two such crews could stabilize about one acre of site per day.
What are some of the best uses for Mechanical Concrete®?
The following is a partial list of current practical economical and beneficial construction uses of Mechanical Concrete®:
• Highway bases and shoulders for concrete and asphalt paved roads and stone surface rural roads of all climates subject to the range of loading from low volume to heavy industrial loadings
• Retaining Walls and Bearing Walls including low volume roads bridge piers
• Drainage and erosion control structures to reduce water runoff velocity
• High wear highway intersections, pothole and rut repairs and utility maintenance repairs
• Temporary and permanent Bridge Abutments and Foundations for structures and buildings
• Storm water retention structures
• Energy Absorbing Highway and Transportation Crash Barriers
• Residential and commercial building walls and foundations
• Bridge pier scour protection
• Earthquake energy absorbing base isolation
• Park trails & golf cart paths with structural French drain characteristics
• Permeable retaining walls for repair and reconstruction
• Railway ballast reinforcing and stabilization
• Foundations for modular housing
• Soft subgrade stabilization for roads, railroads, sites and structures
• Industrial off-road construction, drainage control and stabilization
• Dams, levees, embankments
• Mining facility structures & conveyor foundations
• Water, other liquids and gases filtration systems
• Permeable surface and base for residential and commercial permeable driveways
• Security walls and sound walls
• Military force and facility protection
• Facility security walls and barriers