Engineering and construction. Wood. The Romans created fireproof wood by coating the wood with alum. Stone. It was ideal to mine stones from quarries that were situated as close to the site of construction as possible, to reduce the cost of transportation. Stone blocks were formed in quarries by punching holes in lines at the desired lengths and widths. Then, wooden wedges were hammered into the holes. The holes were then filled with water so that the wedges would swell with enough force to cut the stone block out of the Earth. Blocks with the dimensions of 69 by 14 by 15 ft (21.0 by 4.3 by 4.6 m) have been found, weighing about 1000 tons. There is evidence that saws were developed to cut stone in the Imperial age. Initially, Romans used saws powered by hand to cut stone but later went on to develop stone cutting saws powered by water. Cements. The mixture ratio of Roman lime mortars depended upon where the sand for the mixture was acquired. For sand gathered at a river or sea, the mixture ratio was two parts sand, one part lime, and one part powdered shells. For sand gathered further inland, the mixture was three parts sand and one part lime. The lime for mortars was prepared in limekilns, which were underground pits designed to block out the wind. Another type of Roman mortar is known as pozzolana mortar. Pozzolana is a volcanic clay substance located in and around Naples. The mixture ratio for the cement was two parts pozzolana and one part lime mortar. Due to its composition, pozzolana cement was able to form in water and has been found to be as hard as natural forming rock. Cranes. Cranes were used for construction work and possibly to load and unload ships at their ports, although for the latter use there is according to the "present state of knowledge" still no evidence. Most cranes were capable of lifting about 6–7 tons of cargo, and according to a relief shown on Trajan's Column were worked by treadwheel. Buildings. The Pantheon. The Romans designed the Pantheon thinking about the concepts of beauty, symmetry, and perfection. The Romans incorporated these mathematical concepts into their public works projects. For instance, the concept of perfect numbers was used in the design of the Pantheon by embedding 28 coffers into the dome. A perfect number is a number where its factors add up to itself. So, the number 28 is considered to be a perfect number, because its factors of 1, 2, 4, 7, and 14 add together to equal 28. Perfect numbers are extremely rare, with there being only one number for each quantity of digits (one for single digits, double digits, triple digits, quadruple digits, etc.). Embodying mathematical concepts of beauty, symmetry, and perfection, into the structure conveys the technical sophistication of Roman engineers. Roman concrete was essential to the design of the Pantheon. The mortar used in the construction of the dome is made up of a mixture of lime and the volcanic powder known as pozzolana. The concrete is suited for use in constructing thick walls as it does not require to be completely dry to cure. The construction of the Pantheon was a massive undertaking, requiring large quantities of resources and man-hours. Delaine estimates the amount of total manpower needed in the construction of the Pantheon to be about 400 000 man-days. Hagia Sophia. Although the Hagia Sophia was constructed after the fall of the Western empire, its construction incorporated the building materials and techniques of ancient Rome. The building was constructed using pozzolana mortar. Evidence for the use of the substance comes from the sagging of the structure's arches during construction, as a distinguishing feature of pozzolana mortar is the large amount of time it needs to cure. The engineers had to remove decorative walls to let the mortar cure. The pozzolana mortar used in the construction of the Hagia Sophia does not contain volcanic ash but instead crushed brick dust. The composition of the materials used in pozzolana mortar leads to increased tensile strength. A mortar composed of mostly lime has a tensile strength of roughly 200 kilopascals (30 psi) whereas pozzolana mortar using crushed brick dust has a tensile strength of 3,000 kilopascals (500 psi). The advantage of using pozzolana mortar in the construction of the Hagia Sophia is the increase in strength of the joints. The mortar joints used in the structure are wider than one would expect in a typical brick and mortar structure. The fact of the wide mortar joints suggests the designers of the Hagia Sophia knew about the high tensile strength of the mortar and incorporated it accordingly. Waterworks. Aqueducts. The Romans constructed numerous aqueducts to supply water. The city of Rome itself was supplied by eleven aqueducts made of limestone that provided the city with over one million cubic metres of water each day, sufficient for 3.5 million people even in modern times, and with a ...
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