Project:
Roman Inventions.
CONCRETE
● The Romans first began building with concrete over 2,100 years ago;
● Many ancient Roman structures are still standing today thanks to the
development of Roman cement and concrete. The actual examples are:
» The Pantheon
» The Colosseum
» The Roman Forum
● They used it throughout the Mediterranean basin in everything from:
» aqueducts and buildings to
» bridges, monuments and temples.
● Roman harbors are the most eloquent examples of the sturdiness of the
roman concrete;
● Many of them stand almost intact after 2000 years or more;
● An illustrative example is the harbor from Pozzuoli Bay, Italy.
● By analyzing the mineral components of the cement taken from the Pozzuoli
Bay breakwater an international team of researchers was able to discover
the “secret” to Roman cement’s durability.
● The Romans made concrete by mixing lime and volcanic rock to form a
mortar.
● To build underwater structures :
this mortar seawater
water molecules
and volcanic packed into wooden hydrated the lime
forms and reacted with
tuff chemical reaction
the ash
calcium- EXCEPTIONALLY
aluminum- STRONG
silicate-hydrate BOND
(C-A-S-H)
● For structural mortars,there was initially used volcanic ash, found in regions
around the Gulf of Naples, especially from near the modern-day town of
Pozzuoli. Its virtues became so well-known that ash with similar mineral
characteristics–no matter where it was found in the world–has been
dubbed pozzolan.
● Pozzolana makes the concrete more resistant to salt water than modern-day
concrete.
● The researchers used an ancient recipe written down by Roman architect
Vitruvius to mix a batch of mortar. The engineers let it harden for six months
and looked at it with microscopes. They found that clusters of a dense
mineral form through the Roman process. These stratlingite crystals, formed
by the volcanic sand as it binds with limestone, prevented the spread of
cracks by reinforcing interfacial zones.
● One of the most unusual Roman structure depicting their technical
advancement is the Pantheon, a brick faced building that has withstood the
ravages of weathering in near perfect condition, sitting magnificently in the
business district of Rome.
● Above all, this building humbles the modern engineer not only in its artistic
splendor, but also because there are no steel rods to counter the high
tensile forces such as we need to hold modern concrete together.
● The Romans used a technology based on the density of the concrete. So that,
the aggregate of the upper dome region consisted of alternating layers of
light tuff and pumice, giving the concrete a density of 1,350 kg/m3. The
foundation of the structure used travertine as an aggregate, having a much
higher density of 2,200 kg/m3.
● The pozzolanic cement has much in common with its modern
counterpart, Portland cement. The high silica composition of Roman
pozzolana cements is very close to that of modern cement to which blast
furnace slag, fly ash, or silica fume have been added.
● By comparison, Portland cement lacks the lime-volcanic ash combination,
and doesn’t bind well compared with Roman concrete. Portland cement, in
use for almost two centuries, tends to wear particularly quickly in seawater,
with a service life of less than 50 years. In addition, the production of
Portland cement produces a sizable amount of carbon dioxide. According to
Paulo Monteiro, a professor of civil and environmental engineering at the
University of California, Berkeley, and the lead researcher of the team
analyzing the Roman concrete, manufacturing the 19 billion tons of
Portland cement we use every year “accounts for 7 percent of the carbon
dioxide that industry puts into the air.”
● Recent scientific breakthroughs examining Roman concrete are gathering
media and industry attention. Because of its unusual durability, longevity
and lessened environmental footprint, corporations and municipalities are
starting to explore the use of Roman-style concrete in North America,
substituting the volcanic ash with coal fly ash that has similar properties.
Proponents claim that concrete made with fly ash can save up to 60% of the
cost because of less aggregate use, lessen the environmental footprint by
having a lower cooking temperature, with a much longer lifespan.
The End
