Concrete inFocus - Spring 2014 - (Page oc1)
infocus online connections: corporate suite
Putting common sense to work when
debating the fuel-saving advantages of
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
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
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