Concrete inFocus - Spring 2014 - (Page oc1)

infocus online connections: corporate suite www.nrmca.org/news/connections Mileage Myths Putting common sense to work when debating the fuel-saving advantages of rigid pavement Jon Hansen I bought a new bicycle last fall. No, not one of those bent-over narrow-seat jobs that I rode in my youth. This one's called a "comfort bike" and is designed for the "mature rider," with high handlebars, peddles forward and a wide seat with a backrest. Not a true recumbent style, but a very comfortable bike you can ride for hours without feeling you need to stop at the chiropractor on the way home. As every semi-serious bike rider will tell you, one of the final steps before every ride is topping off your tires. A tire inflated to its maximum pounds per square inch, or PSI, has less rolling resistance and makes peddling easier. Whether it's related to human power or horsepower, reducing rolling resistance is the key element to making things move. If you reduce the rolling resistance on a bike, you travel farther on roll out (that section of flat land that requires no peddling), burning less energy in the form of calories. If you reduce the amount of horsepower it takes to travel a section of road, you reduce the amount of energy generated to create horsepower, thus reducing the amount of fuel. Until someone perfects a perpetual motion machine, those facts cannot be changed: It takes energy to move an object and it takes fuel to create energy. It is this simple rule as to why better fuel mileage is realized on rigid pavements than on flexible pavements. Still not convinced about the effect of rolling resistance? Is your thinking being influenced by reading what some people say about smoothness of a flexible pavement being more important than the stiffness of a rigid pavement? Try this little experiment. Roll a marble across a table. The hard marble and rigid tabletop has very little rolling resistance so the marble will roll until it falls off the table. Even rolling over a crack where the table halves come together may cause a bump, but the marble continues to roll. Now cover the table with a cloth. Take the marble and roll it on the surface the same as you did before. Even though the cloth provides a smooth surface and removes the bump at the crack, the marble will soon stop rolling because of the resistance caused by the cloth. Need another example? Next time you're at your favorite store pushing a shopping cart, notice how much harder it is to push the cart when you go from a hard floor surface to a carpeted floor surface. Same cart, both floor surfaces considered to be smooth, but the more rigid the interface at the cart wheels to the floor, the less rolling resistance. The concrete industry along with various universities and the Concrete Sustainability Hub at MIT have all published research that support an improvement in fuel mileage when traveling on a rigid pavement compared with a flexible pavement. A Florida International University study found a 3.8 percent increase in miles per gallon (MPG) when traveling on rigid instead of flexible pavement. A University of Texas-Arlington study determined a range of 3 to 17 percent improvement, and an Arizona State University report states that 18-wheelers could improve MPG by as much as 20 percent on rigid pavement. MIT converts the numbers into gallons by stating that in the United States, "approximately 740 million gallons of excess fuel is consumed per year due to the use of flexible type pavements." How do you use these numbers to effect change where you live? Here is a grassroots' exercise that will help you show how everyone in your community can keep more money in their pocket by just changing the road surface material they drive on daily. First, select a section of flexible pavement roadway that is commonly known to everyone in the area. Next, find out what the annual average daily traffic (AADT) is for that section of road. It does not matter if you live in a big city, a small town or in the country: someone knows what the AADT count is on every road. You might have to go to the city engineer, public works department, county engineer or state Department of Transportation, but first check the Web as some cities and states now list the information online. The AADT information will normally tell you what percentage are trucks and what percentage are cars or it will show it in actual numbers of trucks and cars. Next, make a reasonable assumption of the average MPG for trucks and the same for cars. My suggestion would be to use 5 MPG for trucks and 15 MPG for cars. The actual MPG numbers you use should be reasonable and consistent. Next, take the number of trucks and multiply by the length of miles traveled on the road, then divide by the MPG to determine the number of gallons of fuel used every day to travel that section of road. Do the same for the cars. Then apply one of the fuel-saving percentages mentioned above to determine the estimated gallons that would be saved. Finally, multiply the gallons saved by the prevailing cost per gallon and you have the potential cost saved per day by the commuting public on that section of roadway. To give the numbers more impact, multiply it out to a year of savings or the years of service. Then multiply it by similar roads or total flexible roads in the area. The numbers will be big and big can get attention. An example from Florida revealed, "If all pavements in Florida were rigid, this could amount to an annual fuel savings of over concrete INFOCUS ı OC1 http://www.nrmca.org/news/connections

Table of Contents for the Digital Edition of Concrete inFocus - Spring 2014

Emergence of Compressed Natural Gas
MMC Materials Converts to Compressed Natural Gas
Fuel Saving Tips from Coast to Coast
Responsible Sourcing for Concrete
NRMCA Services and Tools
Index of Advertisers
Corporate Suite
Concrete Mixer Trucks and the Environment: Get the Connection?
Pavement Roughness and Fuel Consumption
CEMEX ‘Job-Safe’ Program Wins NRMCA 2013 Innovation in Training Award

Concrete inFocus - Spring 2014

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