Nick Orsi (2013)
The infrastructure of a city is the foundation on which civilization is built upon. Formally defined here, infrastructure can be thought of as any underlying foundation used to provide goods and services for the growth of a community (EPA, 2009). Roadways in particular are an important aspect to any infrastructure. In order for a civilization to develop, it is necessary for information, wealth, and trade to flow within and out of the civilization. Roadways are a key solution to this problem. In fact, transportation today can contribute up to 12% of a country’s GDP (Rodrigue, 2013). Recently, the US infrastructure was evaluated and graded by the American Society of Civil Engineers (ASCE, 2013). In regards to the roadways, the US was given a D (“ASCE 2013 Report…”, 2013). In order to improve this grade, it may be beneficial to look upon the roadways of ancient civilizations, specifically the Via Appia of Ancient Rome.
To gain an understanding of the Via Appia and any potential applicable engineering techniques, this report includes several sections on the Via Appia. The first is a history of the road including the reasons it was built, who built it, and what it has been used for. The second section explores the engineering behind the Via Appia. This incorporates how it was designed, what materials were used, and how it was constructed. Next, an on site tour describes the condition of the road, how the road is used now, and any aspects of the road that may be of use for current roadwork. Finally, a section is dedicated to reviewing the continued use of these aspects in modern roadwork, which is followed by a short conclusion.
History of the Via Appia Antica
This overview of the history of the Via Appia is made up of three subsections. The first examines the reasons for the construction of the road. The second section includes a brief history of the man who pushed for the construction of the road, Appius Claudius Caecus. The final section examines how the road has been used since its construction.
Reasons for Construction
Throughout the 4th century BC, the Roman Republic expanded its borders and attempted to unify all of Italy under the Roman Republic. The expansion of the Roman border with time can be seen on the map in Figure 1. As shown, the growth of the Roman Republic stemmed north and southwards during the 4th century BC, nearly quadrupling its original size. One of Rome’s earliest conflicts was the Samnite Wars, a series of three wars spanning more than half a decade. The Samnite Wars represented one of Rome’s most decisive conflicts, as the result determined whether Italy would remain a collection of independent nations or would be ruled by the Roman Republic (Morey, 1901).
The Samnites were a collection of four, Oskan speaking tribes living within the southern central Appennines. The tribes lacked any established currency and conducted little trade, instead supporting themselves on warfare, raiding, crop production, and stock-raising. In times of war, these tribes would unite under a single leader until the defeat of the common enemy (Cornell, 1995). In 343 BC, this common enemy was the Roman Republic during the First Samnite War. Although the Romans and Samnites had been united in a previous alliance made in 354 BC, the Roman’s decided to come to the aid of the Campanians after they appealed to the Romans for help against the besieging Samnites (Cornell, 1995). Both the Romans and the Samnites hoped to gain the use of the rich and fertile lands of the Campanians, explaining why the Roman’s decided to break their alliance with the Samnites. Despite a strike within the Roman army during 342 BC, the Samnites were defeated the following year in 341 BC and a peace treatise was signed (Grant, 1978).
Due to its military success, the Roman Republic began to expand and colonize eastwards. One of the colonies established was located in Fregellae on the River Liris in 328 BC. The Samnites, who had taken control of the region several years prior to the Roman’s colonization, took this as an act of aggression and in response took over Naples in 327 BC, officially starting the Second Samnite War (Grant, 1978). Rome quickly drove the Samnites out of Rome, but in 321 BC the Romans suffered one of the worst defeats in their history at the Caudine Forks. The Roman army was forced to surrender, draw out of the newly colonized land in Fregelle, and stop fighting for nearly five years (Grant, 1978). Rome needed a new way to fight the Samnites to end the war and redeem their humiliating surrender. The answer to this problem came around the year 312 BC from a censor named Appius Claudius Caecus.
Appius Claudius Caecus
Not much is known of Appius Claudius Caecus during his younger life. This is due to the early misfortunes of the Claudius family, whose name does not become prominent in history until Appius. The name Appius comes from his grandfather of the same name who held meager positions in the Roman Republic. Appius was given the name Caecus, meaning the blind, when he was afflicted with blindness in his old age (MacBain, 1980).
In 312 BC, Appius applied for and received the position of censorship. Perhaps knowing he lacked respect and support from his surrounding colleagues due to his family’s status, Appius sought to increase his image with the public and build his clientela. MacBain even argues “most of Appius’ political acts can be seen as innovative devices for winning and rewarding clients,” (MacBain, 1980). In fact, one of Appius’ first acts as censor was to order for the construction of two major civil projects. One was Rome’s first aqueduct, which brought fresh water from the Sabine hills into the city of Rome. The second was the construction of a road running from Rome to Capua. These were aptly named the Aqua Appia and the Via Appia (Cornell, 1995).
Appius’ political career continued well into the 3rd century BC. During this time, he made several efforts to increase the life of the plebeians, one being the public release of the correct forms of legal procedures (Grant, 1978). Appius’ political career ended in 279 BC after he successfully convinced the Republic to turn down the peace treatise offered by the Pyrrhus (MacBain, 1980). Despite this later work, it is the continued use of the Via Appia that has cemented Appius Claudius Caecus’ name in history.
Uses of the Via Appia
First and foremost, the Via Appia was built as a military instrument. The Roman Republic wished to create a strong offensive against the Samnites and establish their hold on the fertile lands within Campania. For this reason, the Via Appia was built from Rome to Capua, the capitol of Campania (Cornell, 1995). Construction of the compacted, gravel finished Via Appia began in 312 BC and was completed around 308 BC (Berechman, 2002). There is some debate as to the exact distance of this section of the road. Grant believes the road to be 132 miles, while Thompson writes the road to be 122 miles. Berechman cites Laurence as the road being 115 miles long. In any case, the road became a key instrument in the Second Samnite War for two reasons. The first was the added protection the Via Appia provided to travelers. The Via Appia mostly traverses the coastal plain, and thereby avoided possible Samnium attacks previous inland routes were susceptible to (Grant, 1978). The second reason was the increased mobility of troops, couriers and supplies between Rome and the southern offensives. This was due to the incorporation of large, straight compacted road segments into the Via Appia. These sections allowed large armies to move 25 miles per day even in the presence of inclement weather, as road disintegration through heavy use was mitigated and the straight nature of the road reduced wasted travel time (Thompson, 1997).
The advantages provided to the Roman army by the Via Appia made it a key instrument in the Rome’s advancement into the Samnite territories, and a mere four years later the Second Samnite War ended with the Romans victorious (Laurence, 1999). The end of the war was by no means the end of the Via Appia though. In fact, the success of the initial construction of the Via Appia from Rome to Capua led to the continual extension of the Via Appia, crossing Italy from the West Coast to eventually end at the East Coast town of modern-day Brindisi by 264 BC. Figure 2 shows the pathway of the Via Appia, starting at the Palantine hills and ending at Brindisi for a total distance of about 360 miles (Berechmen, 2002).
Such a connection from coast-to-coast provided not only a means to protect the lands and colonies established after the Third Samnite War, but also a highway of commerce. With the coast-to-coast Via Appia and the formation of the Roman Empire, standardized trade flourished from Rome to the surrounding provinces. The expanded trade brought vast wealth back to Rome, which more than paid off the estimated 259 million sestertii construction cost of the original stretch of the Via Appia (one million sestertii equals about 2500 metric tons of wheat). During the Roman Empire about 435446 tons of wheat, or 174.2 million sestertii, were transported to Rome annually (Berechman, 2002). This means one and a half years of the wheat transported to the Roman Empire alone accounted for the cost of the original Via Appia (Berechman, 2002). This doesn’t even account for the other valuables the Via Appia helped to bring to Rome, including gold, silver, and iron, as well as providing an affective means to protect the growing Roman Empire.
The Via Appia has since been the site for several historical events. Along the Via Appia, Crassuss crucified nearly 6,000 followers of the slave revolt led by Spartacus after their defeat in 71 BC (Grant, 1978). In 64 AD, St. Peter became a martyr for the Christian faith after turning back from his escape along the Via Appia. According to legend, St. Peter was escaping persecution from Rome when he experienced a vision of Jesus Christ along the Via Appia. St. Peter famously asked “Domine, quo vadis?” (Lord, where are you going?). Jesus replied, “I am going to be crucified again,” causing St. Peter to return to Rome and face martyrdom. Today there is the Domine quo vadis church commemorating this event (Via Appia, 1995). More recently, portions of the surviving Via Appia (known as the Via Appia Antica) were used in the 1960’s Olympic games as part of the marathon course (The Games, 1960). Today parks, monuments, and private residences surround the surviving Via Appia Antica. For over 2300 years the Via Appia has stood the test of time and continues to be in use due to the excellent engineering behind its creation.
The Engineering Behind the Via Appia
This overview of the engineering behind the Via Appia is made up of three subsections. The first describes how the Via Appia was designed. The second covers what materials were used to construct the Via Appia. This section then ends with how the Via Appia was constructed.
Design of the Via Appia
Much time was spent on the design and stakeout of the Via Appia. Several design features were incorporated into the Via Appia to meet the initial military requirements. One was the straightness of the Via Appia. This straightness was important for several reasons. One was the reduced travel time it allowed. Given a flat terrain, a straight line from origin to destination is always the fastest route. The other reason has to do with the ease of surveying straight lines, an important consideration during Ancient Rome as many of the surveying techniques took a lot of time, effort, and could be inaccurate (Berechman, 2002). Scholars are not certain of how the Romans surveyed straight roads. One possibility is the use of fire beacons, which were lit around dusk and laboriously aligned to form a straight line, also known as a primary alignment (Nardo, 2001). Another possibility is the Romans used precision maps, constructed by a network of triangles and marked with the elevation of the surrounding area, to choose a route for the road. The Via Appia was plotted as a series of straight segments, which diverted sharply to avoid obstacles, and only curved when passing unavoidable mountainous terrain (Berechman, 2002). Using this route, the road was outlined using a collection of surveying tools, the most important of which were the diopters and surveying poles. The diopter, shown in Figure 3, was a surveying instrument used to measure angles and distances (Gallo, 2006). Once outlined, stakes would be driven in intervals to mark the placement of the road (Nardo, 2001).
Another important feature was the Via Appia being wide enough to allow two carts to be moving in opposite directions, one on either half of the road. In fact the term via is used to describe this exact feature (Nardo, 2001). The Via Appia varied in width depending on the location of the road section. For example, the minimum was thought to be around 8 feet wide at areas of difficult construction, such as a mountainous pass. The road would then increase to an average width of 10 feet, and just before entering the Roman gates, would increase to 30 feet (Casson, 1994). This width was marked using measurements and digging parallel ditches along the outlined stakes mentioned above. Between these ditches the segments of the Via Appia were built (Berechman, 2002).
The final important feature designed for the Via Appia was the outer surface. Here, design focused on the type of material and shape of the surface to mitigate road degradation. It is unclear how the Via Appia was originally surfaced. Although sections of the Via Appia today are paved with large blocks of stone, it is thought this paving was incorporated sporadically in the road up until 121 BC, and only in sections rather than its entire length (Berechman, 2002). Such a finishing is known as via silice strata. What is more probable is the Via Appia was originally finished with compacted gravel in order to reduce the initial cost and time spent on the road. This finish is known as via glarea strata (Nardo, 2001). Both surface types created a tougher and longer lasting road compared to those surfaced with dirt. Whether using gravel or stone blocks, the Via Appia was designed with a crowned middle. This helped to drain water from the road, improving the lifetime and usability of the road throughout the seasons (Nardo, 2001). The next phase involved gathering and determining the materials to be used in the construction.
Materials used in the Via Appia
In order to construct the Via Appia, large amounts of various materials were required. There is controversy over the types of material used in the road. Becherman writes a study by the US Bureau of Public Roads (1934) on several cross sections of the Via Appia reveals it to be made up of five layers. The first consists of lime mortar or sand. The second involves two layers of stones cemented together with lime mortar or clay. The third layer consists of crushed stones or gravel mixed with lime mortar, sand, or clay. The fourth is made of compacted gravel and hot lime. Finally the road was paved with large basalt stones (Becherman, 2002). This layer system can be seen in Figure 4. Casson writes this is completely incorrect and says recent examination of roads in general revealed there was no use of cement in Roman roadwork, and that they were typically made of only three layers. These were a layer of reinforcing flat stones, a layer of rounded stones within clay, and a gravel or type of igneous rock pavement layer (Casson, 1994). This layer system can be seen in Figure 5.
Something the scholars do agree upon is how the materials used on certain sections of the road were entirely dependent on the soil and surrounding terrain they were building upon. For example, if the Romans found the ground to be sufficiently firm enough, the foundation layers were completely left out and the paving stones or gravel layer was placed directly on top of this soil (Casson, 1994). Another point of agreement is the dependence of the surrounding land for the construction materials. Generally, the materials used in the foundation layers were supplied from the initial clearing of the road. Sometimes this was not the case though. An expensive solution was to transport the material from another site, which was usually within a couple miles of the work site. Alternatively, the Romans could adapt and actually change the road construction based on the available material and surrounding soil and terrain. For example, if stones were short in supply but sand or clay was abundant, then several of the foundation layers could be made with a mixture of these materials (Becherman, 2002). Whatever the solution, after the Romans acquired the necessary materials the construction of the Via Appia could begin.
Construction of the Via Appia
The laborers of the Via Appia were largely made up of freed men and Roman citizens enrolled by Appius Claudius, who wanted only non-members of the political elite to be involved in this civil project (Berechman, 2002). The laborers were provided spades, picks, mattocks, and hammers to carve out the path of the road while baskets were used to transport unused material from the site (Casson, 1994). Construction began with the clearing and loosening of the route and digging of parallel ditches. These ditches were usually 40 feet apart, 3 to 4 feet wide, and were as deep as the road foundations. These ditches served two purposes. One was to help gather building material for the road. The second was to help divert rainwater away from the road to avoid potential flooding and degradation of the road (Berechman, 2002). These ditches were only present when the space and terrain could allow it.
Next, a trench was dug between the ditches in a step known as fossor, or excavation. The depth of this trench varied depending upon the soil. The goal was to reach a firm and stable point to build from, meaning the soil is mostly made up of rocks (Casson, 1994). This was important, as the Romans wished to avoid any chance of settling occurring on the Via Appia, which would quickly deteriorate the road when subjected to the load forces of traveling armies and trade (Nardo, 2001). This step could take quite a bit of time depending upon the soil. In most cases, the laborers had to dig down to about 3 feet. In order to remove all of the useless debris, baskets were passed down on ramps leading from the surface to the bottom of the trench, filled, and removed from the site. Once cleared, the bottom of the trench was then compacted and leveled (Berechman, 2002). A sketch of what this may have looked like can be seen in Figure 6.
Now is the point where the construction of the Via Appia could vary greatly. Depending on the depth of the dug out trench and the firmness of the soil underneath, the Romans could either add the surfacing layer directly at this point, or would have to begin adding foundation layers. This report will examine the most difficult scenario following the five-layer process described in Berechman’s case study, even with its inclusion of lime mortar. Although there is controversy as to whether cement was used in the Roman roads, Casson neither provides a real reason why Romans would not use it or cites specific references to his claim. On the other hand, Berechman does cite a specific study by the US on cross sections of the Via Appia. For this reason this report follows Berechman’s five-layer list.
The first layer from the ground up is known as the bedding, or pavimentum. This layer was made of lime mortar or sand, depending on the available material. It could be 9 inches thick and was used to further smooth out the trench. This layer was compacted, raked, and smoothed out before adding the next layer (Berechman, 2002). This layer involved no skilled labor, as it required mostly mixing and pouring of the materials. Also, due to the thickness and the type of materials required, this layer most likely had abundant material to construct with.
The next layer is the first base layer, or the statumen. This layer consisted of 2 inch thick stones gathered from the clearing of the road. These stones were placed in rows above the pavimentum layer with lime mortar or clay, filling in the empty spaces between and binding together the stones. This layer could vary in depth, from as little as 10 inches to as much as 2 feet. Unlike the previous layer, skilled labor was required in order to cut-fit and place the stones (Berechman, 2002). Due to its potential depth, it can be reasonable to believe this layer may have been compromised by a lack of material, perhaps forcing the Romans to rely more on clay or lime mortar than the thick stones to make up this layer.
The following layer is the second base layer, or the rudus. This layer could be 9 inches thick and involved first a layer of lime mortar, sand, or clay, on top of which gravel or crushed rock was poured onto. The layer was then tamped and displayed characteristics similar to concrete (Berechman, 2002). Judging by the material and depth of this layer, two things could be inferred. One is little to no skilled labor was necessary to complete this layer, only requiring mixing, placing, and tamping of material. The next is this layer would have readily available material due to the small size of the necessary stones and the amount of alternative bindings that could be used.
The next layer was the upper-base layer, or the nucleus. This layer consisted of multiple layers of pressed gravel mixed with hot lime, allowing it to bind to the previous layer. Here, the crown of the road is defined by a 1-foot thickness at the roadside increasing to a 1.5-foot thickness in the center of the road (Berechman, 2002). This layer marks the end of the construction of the original Via Appia. Again, because of the materials and process of construction, this layer probably did not require any skilled labor and would have had readily available material in order to construct.
The final layer added to the Via Appia after its original construction was the pavement, or the summacrusta. This layer involved 6-inch thick igneous rocks, usually basalt, with a diameter of about 1-foot each. These were cut into irregular polygons and fit together with such delicacy as to form a completely smooth surface (Casson, 1994). It is understandable why this surfacing was not originally done, and why it is estimated it only occurred in segments and not along the entire Via Appia. This layer would have required a high level of skilled labor in order to cut and fit the rock as described (Berechman, 2002). Also, the rock would be heavy to transport, and if not readily available from surrounding volcanic areas, would be extremely expensive to transport. Figure 7 provides some insight into the size of the paving stones used.
The above construction process was carried out in various degrees in straight segments along the Via Appia, with obstacles such as marshes, rivers and valleys, and mountains requiring additional construction steps. When passing through marshes, as the Via Appia does along the Pomptine marches, workers would dig and fill a trench with stones, compacting it with rollers and oxen until there was no more observable settlement. Another option was to stack a wooden pier into the marsh, build a wooden frame atop this, and then finish with a layer of gravel (Casson, 1994).
Another obstacle included rivers and valleys. The Romans had several options to cross these points. One was to fill the river or valley with stones or debris, which retained the straightness of the road but diverted the flow of the river. This option could take quite a bit of time and use up a lot of material. Another option was to follow the river or valley from the above or side embankments, which resorted to curving the road and adding travel time. The last option was to bridge over the river or valley, which was expensive and used much material (Casson, 1994). The Romans usually picked whatever the cheapest option was.
The final obstacles were mountains. These often caused workers to reduce the lane widths to pass along natural routes, or were avoided entirely. Another possibility was to carve a path through the mountain, as was done when a 126-foot tall rock slab was carved away along the mountainous coast near Terracina (Berechman, 2002). Given this extensive construction process, it is not surprising several sections of the Via Appia still in use today even after 2300 years of existence.
On Site Observations
This section of the report is made up of three subsections. The first describes the current condition of the Via Appia. The second describes how the Via Appia is used today. The final section focuses on any aspects of the Via Appia that can be used in the modern construction of roads.
Condition of the Via Appia
Today there exists several sections of the original Via Appia, including the Via Appia Antica in Rome. It starts from the Porta San Sebastiano gate within the Aurelian walls and ends nine miles later where the Via Appia Nuova has been laid over the top of the original Via Appia. The road has been under the care of the Parco Regionale Dell’ Appia Antica since 1988 (Povoledo, 2008). The Via Appia Antica has many layers of history incorporated into it. The side of the road is lined with ancient monuments, modern restaurants, and extravagant villas. The Via Appia itself is a strange mixture of history as well, sharply transitioning from the ancient paved stones, to sampietrini, and even modern asphalt, as seen in Figure 8.
The Via Appia Antica retains some key features of the original Via Appia. One is the width of the street. Near the beginning of the Via Appia Antica, the road easily allows for two-lane traffic, and has just barely enough room for foot traffic as well. As the road continues away from the Aurelian Walls and Rome, the width of the road narrows to just barely two lane traffic. This follows with the original intent to accommodate for the heavier traffic near Rome while maintaining the minimum two-lane width along the Via Appia’s entirety.
Another feature that remains is the remarkable straightness of the road. As can be seen in Figure 9, the Via Appia Antica stretches in a straight line as far as the eye can see. In fact, along the first 5 miles there is only one noticeable slight bend, as seen in Figure 10. This again keeps in line with the original intent of constructing a road that travels from one destination to another in the quickest manner possible.
The final noticeable feature maintained is the igneous stone surfacing of the road, although only present in small sections today. Here the large igneous stone paving added after the initial construction of the Via Appia can be seen. The surface is badly worn from over 2000 years of traffic and weathering. Despite this, the original crowned shape of the road is still maintained, and continues to fulfill its original design intent to drain the water away from the road, as seen in the below video.
Another major use of the Via Appia Antica is from the citizens residing in the extravagant villas that line the road, one of which can be seen in Figure 13. Mostly located about 4 miles down the Via Appia Antica and on, these villas are known to contain ancient artifacts and ruins that remain private to the owners. This has been a major issue the guardians of the national park face, as up to 90% of the allotted area remains under private ownership (Povoledo, 2008). Also, extravagant parties are known to occur at these villas, which dramatically increases the traffic on the Via Appia Antica. Because of the location of the villas, cars are forced to travel over some of the few remaining sections of the original igneous stone paving, albeit at a slow pace. This can be seen in the below video. Such traffic further wears down the road to nonexistence, and for this reason it is important to view some of the engineering aspects of the Via Appia for possible use in modern road construction.
Engineering Aspects of the Via Appia
Several important engineering aspects of the Via Appia should be noted. One is the way weathering is reduced by the crowning of the road and the incorporation of ditches on either side of the road. Water is a serious problem to any road. Standing water can make traveling much more dangerous, especially today with the chance of hydroplaning cars. Also the water can seep into the road and undermine the foundation, causing settling and the formation of potholes (Nardo, 2001). This is why it is important to drain the water away from the road and keep it dry whenever possible.
Another important engineering aspect from the Via Appia was the layer system they used in order to create long lasting roads. This system established strong foundations to build upon which has supported various kinds of traffic for more than 2300 years. This layering system was also adaptable, changing whenever necessary to meet the conditions of the soil and available material. The Romans were able to use alternative materials when the primary was short in supply, dig smaller trenches when the firm soil allowed it, and shorten the road width when the terrain demanded it. These aspects saved time and money in construction.
Finally, the Via Appia was constructed through a process of gathering materials on the go. Instead of merely digging up and removing the surrounding soil and vegetation, the Romans used whatever they could find along the way. This included not only the use of sand, clay, and stones, but also existing roads. In fact, the road incorporated the use of the Via delle Terme di Caracalla and the Via di Porta San Sebastiano, thereby reducing time and construction costs (Staccioli, 2013). These techniques also created a green way of constructing by reducing the need of excavating materials from areas outside of the route of the Via Appia and utilizing roads already constructed. It is engineering aspects such as these that have continued to be incorporated into the modern construction of roads.
Modern Transportation Engineering
In the 2013 review of the American infrastructure, the ASCE graded the overall infrastructure with a D+, while giving the roadways specifically a D. This grade should be taken with a grain of salt, given those responsible for the review are likely to gain the most out of a poor review. Regardless, the D signifies the infrastructure in question is in “poor to fair condition and mostly below standard with many elements approaching the end of their lifecycle” (“ASCE 2013 Report…”, 2013). The D was given because 32% of America’s major roads are in poor conditions and 42% of America’s urban highways are congested, both of which are costing Americans billions of dollars in diverting traffic. The basic call to action is to increase funds for the maintenance of existing roads, as building completely new roads has been found to be three times as expensive (“ASCE 2013 Report…”, 2013). Another possibility of improving this grade is to refocus on some of the engineering aspects of the Via Appia to modern road construction.
The engineering of roads today actually already incorporate a lot of engineering techniques used in the construction of the Via Appia. Roads are still built with crowned surfaces and draining systems to divert water away from the road to prevent degradation and increase road safety. Also, the incorporation of multiple layer construction is still used. The traffic roadways experience today are much different than those experienced in Ancient Rome. Todays traffic volume is larger, heavier, and much faster than that in the past. Because of this, not only have the design and materials used to build roadways changed, but a deeper understanding for how the loads interact with the pavement has been developed. Generally, road design can be categorized to two different types of pavement: flexible pavement and rigid pavement (Mannering, 2013).
Flexible pavement generally consists of 4 layers, as seen in Figure 14. The wearing layer consists of some type of asphaltic concrete mix that improves traction for vehicles, protects the lower layers from vehicle abrasion, and waterproofs the structure. The base and subbase layers are aggregate layers. The base layer can be any number of materials from crushed stone to a cement/aggregate mix. The sub base is almost always crushed stone. The final subgrade layer is the soil being built upon (Mannering, 2013). The goal of the flexible pavement is to distribute the traffic loads down to the subgrade over a large area, so the stress from the applied load on the subgrade is relatively lower compared to the point of application (Mannering, 2013). This is down by distributing the load in a conical shape from the wearing layer to the subgrade, as seen in Figure 15.
Rigid pavement typically consists of 3 layer, as seen in Figure 16. The concrete slab can be constructed numerous ways. One method, called the jointed plain concrete pavement, is to have no reinforcement within the slab and connect each slab with doweled joints. Another, called the jointed reinforced concrete pavement, is to have steel reinforced slabs connected with joints (Mannering, 2013). The base and subbase layers are the same as those in the flexible pavement. The goal of the rigid pavement is the same as the flexible pavement, but the method to achieve this is different. The concrete slab is meant to act like a beam, and as load is applied the force is distributed equally along the base layer and down into the subbase, reducing the stress applied onto the subbase layer (Mannering, 2013). This can be seen in Figure 17.
The other engineering aspects used in the Via Appia were the reuse of materials from previously built roads and the use of local materials. These practices make sense not only at an economic level, but also on an environmental level. Today the Greenroads Foundation advocates sustainable roadway design and construction. This foundation provides a point based rating system to certify sustainable transportation projects, which is more fully described in their online manuals. Points are earned by completing voluntary credits, two of which are Pavement Reuse and Regional Materials.
Pavement Reuse involves upgrading or improving previous material to be reused in the new project. This material must be existing within the project boundary, cannot be heavily reprocessed, must be a significant structural element within the project, cannot leave the project boundary at any time during construction (Muench, 2011). This last point differentiates material that is reused and material that is recycled, the later of which is allowed to leave the project boundary. Some examples of pavement reuse could be placing new hot mix asphalt over the preexisting pavement structure, or retrofitting a bridge. Points are earned based on the percentage of the volume or weight of the material reused. For example, 1 is given for a 50% reuse while 5 points is given for a 90% reuse (Muench, 2011).
Regional Materials can be accomplished by one of two methods. The first method is to show a certain percentage of the total cost of materials has been paid to local distributors, processors, and suppliers within a 50 mile radius of the center of the project. Points are earned by reaching certain minimum percentages (Muench, 2011). The other method is to log each basic material (the material in it’s most basic form without changing the chemical composition) along with its respective distance traveled from the origin of production to the destination of the project. Points are earned by showing 95% of the basic materials have traveled below a maximum distance (Muench, 2011). The materials to be considered within this credit cannot be within the Pavement Reuse category. Different projects may favor one method over the other based on the location and size of the project, and it is assumed the easiest method to accomplish will be chosen.
It’s amazing to think such practices as these have been continually used over the 2300 years since the construction of the Va Appia. Perhaps with a reemphasis on the engineering practices carried out by the Ancient Romans, such as the reuse of road material and use of locally gathered material, construction costs could be lowered and the saved money could be used to maintain other roads. Such a shift could not only improve the ASCE grade of the American roadways, but could also decrease the environmental impact our road construction creates, leading to a more sustainable transportation infrastructure.
The Via Appia was a product of both a military conflict and a need for political gain. With its extensive designing and constructive process, it became not only an affective military tool, but also a key part of the economic structure of both the Roman Republic and the Roman Empire. The road has survived the changing landscape, multiple repaving, and a name change to become the Via Appia Antica as it is known today. Even after more than 2300 years of existence, this road remains as not just an ancient monument, but also a sustainable engineering model for the construction of future roadways.
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