What influence did the appearance of concrete have on Roman architecture?

The appearance of concrete caused great changes in Roman architecture. Concrete is a mixture of gypsum, tuff, limestone, bricks and other debris. Roman architects originally used it as a filler and poured it into walls or piers. However, after adding volcanic ash to the mortar, a material with excellent durability was formed, so they began to use this improved concrete more and more boldly from the 2nd century BC. Although the strength of concrete is first-class, its appearance is not beautiful, so the construction workers will coat the surface with a layer of stone, brick or gypsum. These veneers have no structural function, and the veneers have changed in different periods, so they have become a valuable basis for archaeologists to determine the age of buildings. The advantages of concrete soon emerged: it is strong and cheap, and it does not need skilled technology to operate, and it is also very adaptable.

In the past, stones, wood and mud bricks were quite time-consuming or impossible to build. Now, as long as you build a wooden frame and pour concrete into it, you can take shape. In a sense, the history of Roman architecture is the exchange and integration of two forces, on the one hand, the traditional Greek square form and the early Italian beam-column structure, on the other hand, the liberation of architectural form by high plastic concrete. Two very different buildings in China show the advantages of concrete. In the early 2nd century BC, Amelia Colonnade was the earliest known Roman building built entirely of concrete. It was named after the local official who built the first stage. This is a big warehouse in the commercial port area of Rome, which is used to classify and store the goods unloaded from river boats. The scale of the warehouse is amazing: it extends 1600 Roman feet along the Tiber River, with a depth of 300 Roman feet.

Architects use the advantages of new materials to create a very open indoor space. The towering pipe arch covers more than 50 transverse passages and conforms to the slope topography to form four ascending zones. There are arches on the wall supporting the vault, so that workers can see the adjacent areas of any storage area and facilitate the free circulation of air. Another masterpiece of concrete structure is located in the city of Palestrina in the foothills of Apennines in eastern Rome. This magnificent temple is dedicated to Fortuna, the goddess of fate, and its date has been determined as the end of the 2nd century BC or the beginning of 1 century BC. This is an Oracle center where priests read divination to explain God's will. The architect poured concrete on the whole hillside surface, carefully constructed a space to lead and sublimate the viewer's experience. The temple has seven floors, rising layer by layer. On the ground floor, there is an early temple, a rectangular court and a parliamentary hall for citizens to gather. The terrace on the upper floor rises slowly around the central axis, including a series of image niches and steps.

The viewer reaches the third terrace from the side steps, where there is a steep ramp leading to the top, and the ramp is covered with an inclined bucket arch. The sunshine at the end of the ramp leads people to an open platform overlooking the beautiful countryside, and there are other excellent attractions on the platform. The fourth floor is the altar, surrounded by open-air seats with colonnades. The top of the colonnade is covered with a bucket arch, which forms a semicircle in both horizontal and vertical directions. These curved forms make the straight line look smart, because the columns are arranged in a semicircle, and the relationship between the columns and the background will change with each step of the viewer. The broad steps in the middle lead to the next floor. The ramp between the third and fourth floors is covered with vaults, but the steps are open, which reminds people of the erosion of wind and rain. The fifth floor is a shop, which may sell souvenirs and vows.

The viewer's foot is a space supported by a tubular arch, which shows that the builder is full of confidence in this structure. The next floor is an open courtyard surrounded by double colonnades on three sides. The audience will come to the small theater next, with a circular double colonnade at the top. A performance of offering sacrifices to the gods was held here, with the magnificent Campania below as the background. Everyone can see the goddess, and her circular temple is the apex of the whole building complex. Although the scale of the temple is small, it looks solemn because of its overall grandeur. The whole building complex is made of concrete. This material freely adapts to the mountain situation and uses nature to sublimate the religious experience of the viewer. Scholars believe that this temple was built at the beginning of BC 1 century. If this judgment is correct, it may be the dictatorship of Sura. Sura won a great victory in Palestrina during the Civil War. It may even be that he personally ordered the construction of this temple, not only to thank the goddess of fate, but also to commemorate his reputation. To be sure, BC 1 century was a turning point in using architecture for political purposes. One of the most magnificent buildings in this period was Pompeii Theatre, which has been the most important theatre in ancient Rome since then.