An Artificial EarthCache EarthCache
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An Artificial EarthCache-Artificial Stone
Pavement
Street Sign at the EarthCache
Cross Section of the Artificial Stone
Pavement
Imagine Bellefontaine, Ohio in the late 1890s, a the town that was
filled with buggies, wagons, carts, and horses. Now imagine a rainy
day in Bellefontaine. Yes, like all other small towns the street
conditions depended on the weather. When raining, the streets were
muddy, and when dry, the streets were hard and dusty.
Along came George Bartholomew to solve this problem. George
Bartholomew had moved to Bellefontaine, Ohio, in 1886 after having
learned about cement production in Germany and at the San Antonio
Cement Co. of Texas. He had found a location just a few miles
outside of Bellefontaine that had excellent sources of marl. Marls
are calcium carbonate or lime-rich muds or mudstones which contain
variable amounts of clays and calcite or aragonite. Marl is one of
the main ingredients for the production of cement. (This is the
present day location of Marl City, Ohio and where George
Bartholomew had his Buckeye Portland Cement Co.)
After successful experiments in making cement, he started the
Buckeye Portland Cement Co. and began promoting the use of
artificial stone (concrete). An obvious solution to the muddy and
dusty street problems was to use his artificial stone and create a
pavement. The city council was skeptical about this artificial
stone pavement. It was concerned that the artificial stone pavement
would not be durable from the heavy loads on steel rimmed wagon
wheels that travel the streets.
At first the Bellefontaine City Council was skeptical because no
other models of successful artificial stone pavements could be
found. However, in 1891 the city council voted and then authorized
a trial of this new technique. It authorized the paving of a small
eight foot section of a roadway next to the hitching posts. The
trial artificial stone pavement was successful. Still reluctant
Bellefontaine City Council decided to take still another
conservative step with the use of the newly developed artificial
stone pavement. It authorized the paving of the square around the
courthouse, but only on one condition. That condition was that
George Bartholomew would have to be willing to donate the cement
and post a $5,000 bond that guaranteed the pavement would last 5
years. George Bartholomew agreed.
The construction technique employed was similar to that that is
employed for sidewalks today. The slabs were formed in 5 foot
squares with tar paper as the joints between adjacent slabs. The
road utilized a two course pavement system. The bottom, or base
course, was approximately 4 inches thick and had maximum-sized
aggregate of 1.5 inches with a water-cement ratio of 0.60. The top,
or wearing course, was approximately 3 inches had maximum-sized
aggregate of 0.50 inch and a water-cement ratio of 0.45.
The mixing wasn’t done with heavy equipment. All the components
were dumped into a pile and mixed with hand powered screw mixers.
After being mixed it was tamped into forms. This
“mixing-and-placing” method entrapped about 8% air. The concrete
was cured by the continuous wetting of the overlying 2 inches of
sand for a full week. When fully cured, the compressive strength
measured more than 5,000 psi.
George Bartholomew’s artificial stone pavement was considered so
revolutionary that the Chicago International Exposition of 1893
awarded him First Place for Engineering Technology Advancement in
Paving Materials. The concrete pavement turned out to be a
remarkable success. The overall materials and construction costs
(excluding the cost of the donated cement and the bond) was $9,000
and the maintenance and repair cost for the first 50 years was only
$1,400. Obviously, the bond to guarantee the road for 5 years was
really never needed.
To claim a find, please email me the answer
to the questions below. Also you will need to upload a picture of
your GPSr next to your vehicle’s wheel (similar to the second photo
from the top).
Question: What is the length and width of the
remaining section of the America's oldest concrete street?
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