History of light weight concrete

Ancient Applications

Known history of the use of lightweight concrete starts more than two thousand years ago in the Roman Empire. The most significant examples of that time were the Port of Cosa, the Pantheon Dome and the Colosseum (ACI Committee 213, 2003).

The Port of Cosa was built on the west coast of Italy, in 273 B.C. The structural designers of the port were aware of the fact that lightweight aggregates were more convenient to use in marine structures. Instead of using locally available aggregates (beach sand and gravel) for the construction, the builders have brought natural lightweight aggregates (pumice and scoria) from the volcanic resources which were located around 40 km away from the Port of Cosa. The harbour consists of four piers, which had resisted the forces of nature except the surface abrasion for almost 2 thousand years and it is now abandoned only due to siltation (ACI Committee 213, 2003).

The construction of the Pantheon was completed in 27 B.C. It has a dome with a diameter of 43.3 m which was the highest record for almost two thousand years. The builders used the lightweight aggregates of varying densities in descending order from the base to the top of the doom. In other words, higher density aggregates were used near the base where the stresses are higher; and lower density aggregates were used near the top where the stresses are lower. When the dome was first constructed, it had a metal cover which was soon removed to be used for another structure. Until it was covered with a lead roof around 15 years back, it had been exposed to the forces of nature for hundreds of years (Holm & Bremner, 2000). Even today, the Pantheon is still in use for spiritual purposes (ACI Committee 213, 2003).

The Colosseum, which is an ancient amphitheatre of massive size with 50 thousand seating capacity, was constructed in 75 to 80 A.D. The foundation of the Coliseum was made of a light weight concrete utilizing crushed volcanic lava as aggregate. Similarly, the aggregates used in its walls were made of porous, crushed bricks. The spaces and the vaults between the walls were made of porous-tufa cut stone (ACI Committee 213, 2003).

Modern Applications

The use of lightweight aggregates after the Romans was limited. This was changed when manufactured lightweight aggregates became commercially available in 20th century (ACI Committee 213, 2003). In 1918, Stephen J. Hyde, a ceramic engineer, patented the process of producing lightweight aggregates through heating and expanding shale, clay or slate in a rotary kiln. At first, the expanded aggregates were used in the construction of concrete ships for U.S. fleet. Later, expanded aggregates started to be used for civilian construction sector.

The first commercial plant for expanded aggregate production was founded in Kansas, in 1920. In 1923, Dan Servey initiated the first production of lightweight concrete masonry units. In 1929, the use of lightweight concrete jumped to high rise construction. 14 additional stories were added to the existing 14-storey building of South Western Bell Telephone Office by using lightweight concrete (Holm & Bremner, 2000).

Starting from the second half of the 20th century, many multi-storeyed buildings were constructed by using structural lightweight concrete. Examples are 42-storey Prudential Life Building (Chicago) with lightweight concrete floors and 18-story Statler Hilton Hotel (Dallas) with all lightweight concrete frame and flat plate floors (ACI Committee 213, 2003).

Today, the applications of structural lightweight concrete extended not only to Highrise buildings but bridges and marine structures also. Stolmen Bridge and Heidrun Tension Leg Platform are significant examples of recent applications.