“Concrete is essentially an artificially made rock, and is one of the most important and lasting of building materials.
Historical proof of concrete’s importance and durability can be found in the Pantheon at Rome, which was built about 117-124 B.C. – more than 2,000 years ago. This ancient structure was built with circular walls about 20 feet thick and a hemispherical dome spanning 142 feet. The concrete used was a mixture of lime, an aggregate of soft volcanic rock and a local earth or clay called “puzzolana” found in the vicinity of Rome.
The following is a timeline of interesting facts about cement and reinforcing steel:
Austrian Engineers made great developments in theory and practice in the 1890’s, and soon the use of structural steel shapes as reinforcement was developed. During the same period, François Hennebique of France and Ernest L. Ransome in the United States were the first to use reinforced concrete in building construction. Ransome, in his early experiments, originated the twisted square bar from which numerous patterns of deformed bars have evolved. The success of these two men encouraged further study on the subject, resulting in several methods of reinforcement being introduced in both Europe and North America.
A.P. Turner of Minneapolis devised a girderless or flat slab called the “Mushroom Slab” in 1906. By that time, the use of reinforced concrete was becoming quite prominent and has increased from year-to-year up until the present day.
Concrete by on its own has very little tensile strength. Therefore, it must be reinforced in some manner that will ensure against rupture or breakage. When the construction is such that tension can occur, reinforcing steel is embedded into the concrete to withstand that tension. The use of concrete and steel together constitutes what is called “Reinforced Concrete.” Reinforced Concrete is a combination of both steel and concrete using the best properties of each, namely the crush resistant strength of concrete and the tension, or pull resistance of steel.
Combination structural members of concrete and reinforced by steel bars, placed so as to carry the tensile stresses are sturdy and reliable. The concrete, besides supplying compressive strength, also supplies the steel with protection from corrosion and fire. Qualified Engineers design reinforced concrete structures, and drawings are made to show the size and location of the reinforcing steel.
It was early in the 1900’s, when the Iron Workers established jurisdiction over the unloading, handling and installation of reinforcing steel for concrete construction. It was not too long until Ironworkers were skilled in laying reinforcing steel. Companies, therefore, found the most efficient way to perform a job requiring the use of this material was to hire members of the International Association of Bridge and Structural Ironworkers. Thereafter, the name of the union was eventually changed to the International Association of Bridge, Structural, Ornamental and Reinforcing Ironworkers.
As the demand for more buildings grew, and construction increased throughout the United States and Canada, so did the demand for more skilled ironworkers. Although many buildings were constructed of steel, many others were of reinforced concrete. The number of skilled workers in this branch of the ironworking trade has increased and today, many buildings, structures and bridges are designed, not only to withstand tremendous weight, but also to conform to modern day Architecture.”