Making wonder: a guide

 

Have you ever wondered just what it takes to build one of the seven wonders of the world? Well today I am here to tell you about one: THE COLOSSEUM. Yes, it deserves the caps lock because this monument is truly stunning. The colosseum stands at an astonishing 50 m high and half a kilometre, you heard me right, 500 m in circumference. So let me take you on a journey of how this amazing monument came to be. Before construction could even begin, an artificial lake constructed by Nero *eye roll* had to be drained.[1] Then, pre-cut tufa and travertine block were delivered to the site and organized based on their height.[2] The foundation was first to be laid, an opus caementicium wall 50m wide and 13 m high.[3] Now that the foundation was laid, the external structure could be built on top. I was certain that they would’ve continued to work from the ground up but of course the Romans are too cool for that. Turns out, based on evidence of extensive scaffolding, that they were actually working on multiple levels at once.[4] Not only were multiple levels being worked on, but many different sections all at once, each with their own work team and contractor. 

The external view of the colosseum where you can see the different levels that would've been worked on simultaneously. 

Credit: Alayna Krueger

We can see the different building techniques that were used within different areas of the colosseum, which sometimes worked out fine and sometimes didn’t and certain areas would have to be redone.[5] The main part of the Colosseum’s external structure consists of the cavea and three ring walls. There were 240 piers for each floor, made of travertine voussoirs laid (they didn’t even use mortar!) and connected at various levels by arches supporting the perimeter arcades.[6] The cavea consisted of radial walls made of stone, two outer layers of coursed ashlars, with an inner rubble and mortar fill and covered with concrete barrel vaults over and then rows of stone seats were built overtop.[7] 

Internal view of the colosseum showing some of the different piers where the seating would've been.

Credit: Alayna Krueger

There’s so much more we could talk about, the underground structures were another phenomenal feat of Roman architecture but unfortunately we are out of time for today. I hope that you get to see this monument in person now and be able to appreciate the amount of labour that went into building this wonder.

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[1] Como, Mario. “The Colsseum.” Essay. In Statics of Historic Masonry Constructions, 2nd ed., 351–88. Switzerland: Springer International Publishing, 2016. 352.

[2] Elia, Giovanni Manieri. "The Colosseum: Quality and efficiency of construction." In Proc., 1st

Int. Congress on Construction History, pp. 1345-1356. 2003. 1346.

[3] Como, 352.

[4] Elia, 1346.

[5] Elia, 1347.

[6] Como, 352.

[7] Como, 355.

Bibliography

 

Como, Mario. “The Colsseum.” Essay. In Statics of Historic Masonry Constructions, 2nd ed., 351–88. Switzerland: Springer International Publishing, 2016.

 

Elia, Giovanni Manieri. "The Colosseum: Quality and efficiency of construction." In 

            Proc., 1st Int. Congress on Construction History, pp. 1345-1356. 2003.

Roman Rooooooaaddss Take Me Hooooooooommee

 

Roman roads paved the way for the expansion of the Roman empire, literally. Clearly, they were doing something right because thousands of years later, we still use very similar road construction techniques. Although road construction was not nearly as focused on in ancient writings as monuments or cities, Statius wrote a poem outlining the technique.[1] Before construction could begin, there were certain factors that played important roles in determining the course of these roads. The most prominent being the topography of the area, in relatively flat landscapes there was more choice in where the road was built but as construction moved through hills and mountains, construction had to become more adaptive to the area.[2] The ditches were the first to be prepared, there wasn’t a set depth for the ditches as many different factors came into play.[3] After the ditches were complete, the road was then constructed in layers. 

Diagram showing the different layers of ancient roads, to be explained in detail. 

Credit: Encyclopedia Britannica

The bottom layer called the stratum, was made of the natural ground that had been dug and levelled and then laid with stones at least 30 cm thick. The next layer was called the rudus, this was made by mixing stones with lime mortar, and was about as thick as the stratum. The next layer, called the nucleus was made of gravel that was levelled and packed down. Lastly the pavimentum, whose composition depended on the importance of the road and the materials available in the area. The pavimentum could be made of gravel, small broken stones, irregular slabs of siliceous stone, hard lime or cut basaltic stones.[4] 

Modern example of what a road with a pavimentum of cut stones looks like. 

Credit: Alayna Krueger 

The construction of roads evolved over time, including adaptation in materials, such as swapping out river sand for volcanic sand which had more mechanical resistance.[5] Evidently this was a very evolved process and took many hours of labour and hard work but just as with everything else, the romans had learned over time how to perfect it. Evident by the sheer amount of roads they built.

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[1] Knapton, John. "The Romans and their roads—The original small element pavement technologists." In 5th International Concrete Block Paving Conference, Tel-Aviv, Israel, vol. 13. 1996. 41.

[2] Bekker-Nielsen, Tønnes. "New approaches to the study of Roman roads." In Report to the 19th International Congress of Historical Sciences, Oslo, vol. 6. 2000. 2.

[3] Knapton, 43.

[4] Corradi, L., S. Rasimelli, M. Marchetti, S. Corradi, S. Batino, and M. Corradi. "The Building

Techniques of the Roman Roads: the Via Flaminia from Narni to Forum Flaminium, in Umbria." In Extraordinary machines and structures in antiquity. Peri Technon, 2001. 120.

[5] Corradi, et al., 121.

Bibliography

Bekker-Nielsen, Tønnes. "New approaches to the study of Roman roads." In Report to the 19th

International Congress of Historical Sciences, Oslo, vol. 6, p. 23. 2000.

 

Corradi, L., S. Rasimelli, M. Marchetti, S. Corradi, S. Batino, and M. Corradi. "The Building

Techniques of the Roman Roads: the Via Flaminia from Narni to Forum Flaminium, in Umbria." In Extraordinary machines and structures in antiquity. Peri Technon, 2001.

 

Knapton, John. "The Romans and their roads—The original small element pavement

technologists." In 5th International Concrete Block Paving Conference, Tel-Aviv, Israel, vol. 13. 1996.

Breaking News! "Lean On Me" by Bill Withers was actually inspired by ancient Roman domes

 

I think that one of the coolest advancements in Roman building styles was the development of semicircular roofs such as domes and vaults. For the Romans to be able to create that type of shape, some of which would survive thousands of years, is truly mind boggling to me. Some domes didn’t even have concrete holding them together![1] Although this didn’t happen overnight, before Romans could build domes, they first had to learn how to make arches and vaults.[2] 

An example of the types of arches that made domes possible. 

Image credits: Alayna Krueger

One of the oldest surviving examples is at the Stabian Baths of Pompeii, this was a conical concrete dome, built at frigidarium, 6 meters in diameter and dates to 120 BCE.[3] Domes were constructed as a series of arches, arranged around a vertical axis through the crown and tied together by horizontal hoop forces.[4] The pantheon in one of the most impressive and in tact examples of this architecture. 

The domed roof of the Pantheon. 

Image credits: Alayna Krueger

It is also a great example of how the ancient architects overcame the problems caused by hoop tension. It has a hemispherical dome inside, the thickness of the upper part is a little over 1 metre, where hoop tension becomes an issue, the thickness increases in steps, this is because more material in the region of the hoop tension, lessens the tensile stress compared to a dome of uniform thickness.[5] 

Aerial view of the pantheon that demonstrates the increased thickness in the region of hoop tension. 

Image credits: Alamy stock photo

The pantheon is just one example of how the Romans were able to overcome structural difficulties when building domes and really goes to show their ability in perfecting their techniques. 

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[1] Usanmaz, Uygar  Ozan. “A GLIMPSE INTO THE ORIGINS OF ROMAN CONCRETE DOMES.” Akdeniz Üniversitesi Sosyal Bilimler Enstitüsü Dergisi, no. 11 (2022): 45.

[2] Usanmaz, 30.

[3] Usanmaz, 34.

[4] Cowan, Henry J. “Domes—Ancient and Modern.” Architectural Science Review 20, no. 2 (June 1977):  doi: 10.1080/00038628.1977.9697235. 183.

[5] Cowan, 183

Bibliography

 

Cowan, Henry J. “Domes—Ancient and Modern.” Architectural Science Review 20, no. 2 (June 1977): 181-198. doi: 10.1080/00038628.1977.9697235.

 

Usanmaz, Uygar  Ozan. “A GLIMPSE INTO THE ORIGINS OF ROMAN CONCRETE DOMES.” Akdeniz Üniversitesi Sosyal Bilimler Enstitüsü Dergisi, no. 11 (2022): 30–52.

Opus Caementicium: stuck between a rock and another rock

 

No matter what site you’re visiting in Rome, you will almost certainly be surrounded by Roman concrete. This type of concrete is known as Opus Caementicium. Use of concrete began around 3rd century BCE and continues steadily throughout antiquity.

Ruins in which you can see the concrete core and the brick facing that hasn't survived in some spots. 

Image Credits: Alayna Krueger

It was popular for a few different reasons. One major advantage was the variability in how you could make the concrete. Roman concrete was made of three main ingredients: slaked lime, inert sand or a pozzolanic additive, and pieces of aggregate. Vitruvius even wrote about this concrete and how to make it, in 27-30 BCE.[1] By changing the type of aggregate that was mixed in, builders could control the density and weight of the concrete.[2] Having this type of control was beneficial because you could make really strong and dense walls but also ceilings that were light enough not to fall. It was also popular because the materials were readily available, Romans didn’t have to look far to find the materials they needed. 

An example of columns that were also made with concrete and stone facing.

Image Credits: Alayna Krueger

Many Roman walls consisted of concrete that was often faced with different types of stone, these walls kind of looked like a sandwich when you could see the concrete core and stone on each side. Sometimes, plaster was then added to the outside to create a more high end look. Although we didn’t get to see any so far, I would also love to see ancient Roman marine concrete, it repairs itself! Sadly, that’s a whole other can of worms that I don’t have time to dive into today.

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[1] Elsen, Jan, Marie D. Jackson, and Encarnación Ruiz-Agudo. “Historic Concrete Science: Opus Caementicium to ‘Natural Cements.’” Elements 18, no. 5 (October 1, 2022): 301–7. doi: 10.2138/gselements.18.5.301.

[2] Ulrich, Roger B., and Caroline K. Quenemoen. A companion to roman architecture. Malden (Mass.): Wiley-Blackwell, 2013. 172.

Bibliography

Elsen, Jan, Marie D. Jackson, and Encarnación Ruiz-Agudo. “Historic Concrete Science: Opus Caementicium to ‘Natural Cements.’” Elements 18, no. 5 (October 1, 2022): 301–7. doi: 10.2138/gselements.18.5.301.

 

Ulrich, Roger B., and Caroline K. Quenemoen. A companion to roman architecture. Malden (Mass.): Wiley-Blackwell, 2013.

Opus Incertum: No it's not a Harry Potter spell

 

While walking around Pompeii, we saw many different types of walls and wall building techniques. The one that intrigued me the most was the opus incertum technique. How do such seemingly random placed stones last 2000 years? Was there a method to the madness? When I found out that this technique is the most commonly found at the site of Pompeii it made me wonder if the builders at the time knew how successful it would be or if they just thought it was the easiest.[1] Based on surveys done by Auterio et al., many consistencies were found within these walls: 1) the stones were not aligned in any way but the smaller ones were used to fill gaps between larger ones 2) lava, travertine and foam lava stones were most commonly used 3) thickness of the walls was between 0.35-0.48 m.[2] However, irregular and discontinues texture is not necessarily the hidden superhero I had hoped for as it in fact does not assure the compactness of the material or monolith behavior.[3] Due to the random placement of stone it does not allow an even distribution of weight and can cause the weakest parts of the wall to crack under pressure, literally.[4] Although it is most common, studies show that opus incertum is not the best option for longevity under stress. Tune in next week to find out what technique might be a better candidate.

Example of an original opus incertum wall in Pompeii.

Image credits: Alayna Krueger

Another example of opus incertum in Pompeii, this one was once covered by plaster.

Image credits: Alayna Krueger

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[1] Autiero, Francesca, Giuseppina De Martino, Marco Di Ludovico, and Andrea Prota. “Mechanical Performance of Full-Scale Pompeii-like Masonry Panels.” Construction and Building Materials 251 (August 2020). doi: 10.1016/j.conbuildmat.2020.118964.

[2] Auterio et al., 4.

[3] Santini, Silvia, Marina Cogotti, Carlo Baggio, Valerio Sabbatini, and Claudio Sebastiani. “Field Testing for Structural Behavior of a Stratified Monumental Complex over Time: Palazzo Colonna-Barberini and Templum Fortunae Praeneste.” Case Studies in Construction Materials 18 (July 2023). doi: 10.1016/j.cscm.2023.e02152.

[4] Auterio et al., 12. 

Bibliography 

Autiero, Francesca, Giuseppina De Martino, Marco Di Ludovico, and Andrea Prota. “Mechanical Performance of Full-Scale Pompeii-like Masonry Panels.” Construction and Building Materials 251 (August 2020). doi: 10.1016/j.conbuildmat.2020.118964.

Santini, Silvia, Marina Cogotti, Carlo Baggio, Valerio Sabbatini, and Claudio Sebastiani. “Field Testing for Structural Behavior of a Stratified Monumental Complex over Time: Palazzo Colonna-Barberini and Templum Fortunae Praeneste.” Case Studies in Construction Materials 18 (July 2023). doi: 10.1016/j.cscm.2023.e02152.

The Battle of the Elliptical vs. the Oval at the Pompeii Amphitheater

In Pompeii, our first stop was the amphitheater. This amphitheater is the oldest one that’s still standing, and it was also one of the first attempts to apply a new geometric scheme to architectural design.[1] When you walk up to the amphitheater, it really takes a minute to appreciate the size of this monument and the fact that it is still standing today despite an earthquake, eruption and roughly 2 000 years. It really makes you wonder how the ancient Pompeiians were able to execute such a feat. The first step was to level the ground, this included excavations of south and east and raising of the north and west sides.[2] [3] This resulted in certain parts of the theatre being below ground level and certain parts of the cavea were above ground level.[4] They then had to measure the shape, this was done using something called a “electronic theodolite,” this device used a reflecting prisma that was moved in intervals to measure perimeter.[5] After applying a variety of analyses to the shape of the amphitheater, Duvernoy and Rosin were able to conclude that the amphitheater at Pompeii was constructed in an elliptic shape, which quite rare in architecture.[6] It was quite amazing to think about how much time, intelligence and care was put into this building. Come back for part two where we will be diving into the materials used to build the amphitheater.

Aerial view of the amphitheater showing the full elliptical shape. 

Image credit: Mike Seaman

Inside of the amphitheater showing the curvature from the inside. 

Image credit: Alayna Krueger

Entrance into the amphitheater showing the downward slope that leads to the portion that is below ground level. 


Image credit: Alayna Krueger

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[1] Duvernoy, Sylvie. “Architecture and Mathematics in Roman Amphitheatres.” Architecture and Mathematics from Antiquity to the Future, April 10, 2014, 189–99. doi: 10.1007/978-3-319-00137-1_13.

[2] Duvernoy, 194.

[3] Dobbins, John Joseph, and Pedar William Foss. The World of Pompeii. New York, New York: Routledge, 2007. 121.

[4] Duvernoy, Sylvie, and Paul L. Rosin. “The Compass, the Ruler and the Computer: An Analysis of the Design of the Amphitheatre of Pompeii.” Architecture and Mathematics from Antiquity to the Future, May 7, 2014, 525–40. doi: 10.1007/978-3-319-00143-2_36.

[5] Duvernoy, 194.

[6] Duvernoy and Rosin, 539.

Bibliography

Dobbins, John Joseph, and Pedar William Foss. The World of Pompeii. New York, New York: Routledge, 2007.

Duvernoy, Sylvie. “Architecture and Mathematics in Roman Amphitheatres.” Architecture and Mathematics from Antiquity to the Future, April 10, 2014, 189–99. doi: 10.1007/978-3-319-00137-1_13.

Duvernoy, Sylvie, and Paul L. Rosin. “The Compass, the Ruler and the Computer: An Analysis of the Design of the Amphitheatre of Pompeii.” Architecture and Mathematics from Antiquity to the Future, May 7, 2014, 525–40. https://doi.org/10.1007/978-3-319-00143-2_36.