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Daniel Brainard
Art History 447
3 / 29 / 2005
Roman Architectural Achievements
Architectural techniques have been evolving and changing for many centuries.
These changes come about due to new discoveries in building materials and advances in
the way various structural elements are used in building. We start seeing changes in
construction methods during the classical era of Greek Art. It is then that the massive
stone temples begin appearing, along with elaborate sculpture decorations. However, the
architectural achievements of the Romans far surpass that of the Greeks. Quite possibly
the most important advance made by the Romans was the continued development of
concrete. The use of concrete revolutionized many of the other current construction
methods of the time. Notably, arches drew great use out of the flexibility of the concrete,
and grew to become one of the most used construction feature. Everything from bridges,
to aqueducts, to building structures were using the new advances in both concrete mixing
and arch building
The formula for making concrete has been known since ancient Egyptian and
Mesopotamian times. The Romans however made a change in the mix that allowed their
concrete to last through centuries of abuse. Roman concrete, (opus caementicium), added
a key material that was stronger then any previous mix, their addition was "pozzolana."
Pozzolana itself was found thought central Italy, and is a finely pulverized volcanic
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product which is very hard and can resist wear and abrasion better than the soft lime
which bound the pieces of gravel together in regular concrete made only of lime, sand
and gravel” (Grant 290). Later it was found that mixing the pozzolana with limestone in
a kiln reduced it into “quicklime”, which remained the best know cement material until
Portland cement was discovered in the 19th century. The mixture would then be mixed
with an aggregate. This aggregate (caementa), was often made of stone chips and other
waste rock from broken building faces and when mixed with the pozzolana and lime
bound it together in a compact mass that was solid and exerted little thrust when set
(Grant 291). There are four main reasons as to why Roman concrete became a huge
achievement of the era. First and foremost, the concrete was stronger then any material
that had been found to date. This exceptional strength allowed the roman architects to
span great distances using new methods which the concrete allowed, such as arches,
vaults, and domes. The already strong concrete was also often reinforced. The Romans,
who obviously did not have the steel rebar that we use today, instead tested various types
of ropes and ceramic rods as reinforcement. The second reason as to why Roman
concrete was so important was the fact that it is such and easily workable material. This
flexibility is due to the methods with which the concrete was applied and used. Unlike
today’s modern methods of pouring concrete, the Romans used a much thicker mix that
we would call a “no slump” mixture that was created by keeping the moisture content in
the concrete low. They would then lay down the base structure of stones and aggregate
and begin forcing the mixture over and into it, creating the solid mass we see. Another
advantage this method had was that changes in the construction could be made very
easily and at the last minute, which was something that could rarely be done with a
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building built of carved stone. In addition, concrete is able to set underwater, so its uses
with bridges and aqueducts were quite widespread. The third reason for the success of
concrete was the low cost and the ease using it. With both key components being easy to
obtain materials, the price of using concrete was much lower the other traditional
building methods. The aggregate was almost always excess materials from other
building projects or waste from structures that were broken or destroyed. In addition to
the low cost of the materials themselves, the actual labor itself cost very little, since
skilled rock carvers were no longer needed to complete the structures. Concrete was also
a much faster material to work with. Architects and construction crews no longer needed
to wait months or years for all of the cut stone blocks. The fourth reason, while a
somewhat lesser issue was that concrete is obviously fireproof. When used to build both
walls and roofs, these structures in effect become much safer then the wooden structures
which were used before.
The one major downfall of concrete was that once the framework was removed,
what remained was a structure of very unsightly rock surface. The Romans however
employed several methods with which to cover this surface. The first method used to
counter these ugly surfaces was to lay slabs of cut tufa (a semi-soft volcanic rock, found
mostly in central Italy) stone as facing, as seen in the picture below. Structures were
started with a simple concrete core then the slabs were bound securely to the surface.
While this method did indeed work to cover the concrete surface, it required skilled
craftsmen and extra time to carve the slabs of tufa. Going back to needing the skilled
carvers in many respects defeated the purpose of using the cheap concrete construction in
the first place.
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When it was realized that the tufa slab method was not terribly efficient, the Romans
began to experiment with other methods of altering the concrete surface. The next
technique used was known as opus incertum. This method took a core structure of
concrete and into this would be set cone-shaped pieces of tufa, with the flat, irregularly
shaped head of the cone facing outwards (Ramage 64). Opus Testaceum was a method
that took rectangular faced bricks, with pointed backsides, and set them into the concrete.
The effect of this technique was a finished facing that appeared to be laid of regular
bricks. The opus reticulatum method became one of the more popular facing methods
which started to be used during the first century BC. This system used the heads of
pyramidal stones or bricks which are characterized by a series of diamond shapes that
give the effect of a kind of net pattern (Ramage 65). This pattern appears as the flat
surfaces of walls between corners of laid brick or stone. According to Vitruvius, opus
incertum is an "ancient style," and opus reticulatum, while not as strong, is the "style
used by everybody” (Geary 3). Probably the best preserved examples of the opus
reticulatum method come from the remains of Hadrian’s Villa. This grand residential
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area of Tivoli is also well known for mixing various facing methods in order to achieve
the most visually pleasing structures.
Close up detail of opus reticulatum, Hadrian’s Villa
Mixed facing, Hadrian’s Villa
In addition to these more basic facings, some of the more wealthy partisans would take it
one step farther. After the initial facing was set, it was often times covered with another
more decorative material. Frequently this added material was plaster or stucco, which
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could then be molded and painted to imitate cut marble masonry if so desired. In some
cases, privately funded structures with large budgets would even employ the use of actual
cut marble slabs. Using thin marble facings, the Romans were able to achieve elegantly
carved half pillars among other decorative features.
Here we see an example of marble facing that has been laid on top of an Opus Testaceum
brick facing. While using these marble slabs again increases labor and price of buildings,
it is quite easy to see how much time, labor, and costs could be saved by using a thin
marble plaque as opposed to huge cut blocks as the Greeks had done.
One disappointing aspect of these extra facing materials is that very few examples
still survive. What we see left on most Roman ruins is only the original opus brick
facings. The concrete and the bricks have been able to stand the test of time quite well.
The plaster, stucco, and marble faces have not had such luck. Much of the plaster and
stucco have simply just not been endure the elements, being slowly destroyed. Much of
the marble facing suffered a different fate. As buildings were abandoned or destroyed,
nearly all expensive materials that might have been in them were taken and reused
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elsewhere. Not only that but under times of attack, buildings were destroyed and looted
of any materials that would be worth anything. The fact that many ancient roman
buildings are in the state they are in now often misled people into believing Roman
architects left their walls with simple brick facings, rather then making any attempts at
elegant design (Grant 293).
The next truly great architectural achievement made by the Romans was the
successful and inventive use of the arch. While it is sometimes said that the Roman
where the designers of the arch, this is not actually the case. The early Etruscans were in
fact the first civilization to make use of the arch, the Great Drain (Cloaca Maxima) is one
such Etruscan arch that survives today (Grant 295). The arch originated with the idea of
placing a considerable number of blocks in a concentric arrangement. The wedge-shaped
blocks, called voussoirs, hold each other firmly in place and prevent each other from
slipping. The voussoirs at the top, or crown, of the arch convert the downward pressure
into lateral outward pressure, or thrust, which is transmitted from the upper voussoirs
down around the opening and finally into the ground through the wall or pier on which
the arch rests. Not only can considerable distances be spanned in this way, but arches can
carry a much heavier load than a horizontal lintel (Arches). In addition to these uses,
arches had a tendency to be much cheaper to use then building a solid wall, due to the
obvious fact that much less material is needed to hold the upper materials up. Arches
however were still not without some weaknesses, especially before concrete was used in
the creation of the arches. With a block constructed arch there is a tremendous amount of
thrust pushing on the lower voussoirs. If any one of these were to get pushed out of
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place to far there is a danger of the keystone slipping out, causing the entire arch to
collapse. This was countered in a couple of different ways. First, was to place several
arches in a line so that the spandrel between the two countered the thrust of the lower
voussoirs. However, on a single arch or at the end of a line of arches this option wasn’t
viable, so instead there is generally a huge bulk of mass on either side of the arch to
counter the thrust. This second method is often seen in triumphal arches.
The advent of concrete use in arches served to eliminate many of the weaknesses of block
arches. The fact that concrete exerts equal amounts of force though out the structure
allowed the arches to become smaller, stronger, and able to span much greater distances.
The development and use of the arch is what allowed the Romans to create the
great buildings and structures that we still see today. Arches first began seeing excessive
use in bridges and aqueducts, and then later started appearing as major structural
elements of buildings. Bridges and aqueducts were a very logical next step for the
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Romans to take with their new arch technology. The ability to span large valleys and
rivers easily arched bridges great utility in the mountainous regions of Italy. An example
of one such bridge is seen in Narni, where the Via Flaminia crossed the river Nera.
The bridge had 4 nearly perfect half circle arches, of which only one still survives today.
It is known from looking at the piers that the arches were not all the same height,
meaning the central arch spanned a much greater distance then the other three. Another
great bridge built by the Romans is located in Alcantra (which means “The Great
Bridge”). This amazing bridge spans the Tagus with six great arches, which rise more
then two hundred feet above the river. Originally constructed in the year 105 AD, the
bridge stood intact until the 13th century when enemy forces destroyed one of the arches.
Since then it has undergone two repairs, allowing it to be in continued use to this day.
In addition to bridges, the Romans used their arch technology to great prevail
while constructing aqueducts. Ancient Rome had eleven major aqueducts, built between
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312 B.C. (Aqua Appia) and 226 A.D. (Aqua Alexandrina); the longest (Anio Novus) was
59 miles long. It has been calculated that in imperial times, when the city's population
was well over a million, the distribution system was able to provide over one cubic meter
of water per day for each inhabitant: more than we are accustomed to use nowadays
(InfoRoma). While in most cases a good portion of the aqueduct system would be simply
bored underground, as Roman building techniques were improved so were the aqueduct
systems. The overall goal was to keep a constant gradation from the source of the water,
all the way into the city. To do this, the aqueducts started being raised up on large arched
runways in order to span valleys and low areas, sometimes rising up to one hundred feet
above ground level. The Aqua Claudia pictured below was one of the many
aqueducts that used concrete construction, due to its waterproof nature. Not all built
using concrete however. The aqueduct at Segovia, which was built during the mid first
century AD, is an excellent example. While still constructed using arches, this particular
aqueduct was built using no mortar or other binding materials. The granite rocks are
precisely carved to fit just into place with each stone below it.
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It is very easy to see that the architectural advances achieved by the Romans not
only benefited them in ancient times, but rather, continued to alter building construction
for centuries. The development of Roman concrete is quite possibly one of the greatest
discoveries in the architectural world ever. Without it many of the amazing structures we
know of today would have never been built. Not to mention that with the development of
concrete came advances in other architectural methods as seen with the arch. Arches had
been used previously without concrete, but had many more limits on the construction. In
addition the continued development of the arch itself is another great achievement. Very
few structures left out the use of arches after the usability was realized.
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Works Cited
Arches. Parts of an Arch.
http://employees.oneonta.edu/farberas/arth/arth109/arch_vaults.html
Geary, Judith. Republican Roman Construction. 2000. Appalachian State University.
http://romanhistorybooksandmore.freeservers.com/l_rrc1.html
Grant ,Michael. The World of Rome. NY: Penguin Group 1960
InfoRoma. Roman Aqueducts. http://www.inforoma.it/feature.php?lookup=aqueduct
Ramage, Nancy, and Andrew Ramage. Roman Art. New Jersey: Prentice Hall. 2005