BRIEF HISTORY OF CONCRETE

The Romans first used a form of concrete around 300 BC consisting of lime, broken stones and sand.  With the discovery of Puzzolana, a kind of natural cement, near Mt. Vesuvius, the Romans were able to create a stronger bond than they attained with lime cement.
Then in 1824, Joseph Aspdin, from Leeds, England, patented a new type of cement made by treating, heating and cooling raw materials into clinker.  These small rock-like shapes, made up mostly of calcium silicate, were then ground to a fine powder.  This is first example of Portland Cement.
Manufacturing of Portland Cement in the U.S. did not begin until about 1872. 
By now, you essentially have a material that is very strong in compression, but possesses no tensile strength.  So, as both of these forces work dynamically on all structural components, an additional material would need to be used within concrete to accommodate these forces.  Reinforced Concrete was first patented by a French gardener name F. Joseph Monier in 1857.  The use of steel, which is extremely strong in resisting tensile forces, was necessary to make concrete as versatile as it is today.  Steel is actually very strong in both tension and compression, but is extremely heavy and combustible.  In my opinion, the combination of concrete and steel is one of history’s most important inventions.
From there, a handful of improvements were made regarding the technique of forming and reinforcing concrete.  Prestressing, the act of stretching the steel reinforcement prior to the curing of concrete, was introduced by a French engineer named Freyssinet in the late 1920s.  Of course we also have the technique of Post-stressing, which stretches steel tendons after the curing of concrete.  The development of Prestressing and Post-stressing both meet the need for concrete to perform under extreme loading or span conditions. 

Today, concrete is made up of five basic components, where their respective proportion by volume is indicated:  Cement (11%), Water (16%), Air (6%), Fine Aggregate (26%), Coarse Aggregate (41%).  Steel is not included in this list because it is not technically needed to make concrete, but is added to varying degrees and design per engineering standards to achieve desired strengths that are otherwise impossible.  The chemical reaction between Cement and Water is what makes adhesion possible, and this ratio is a major determining factor for the strength of the concrete.  So, I consider concrete to be extremely exciting because of the five (or six, if you count steel) components of concrete we’ve really only advanced two or three of them (more on this later).  There are at least three other components that can be experimented with in order to yield cutting-edge development to increase the performance of concrete!  My studies will address the advancement of reinforcement on a nano-scale with the use of Carbon Nanotube technology. 

Source: Simmons, H. Leslie. Construction – Principles, Materials and Methods.  7th Ed. John Wiley and Sons, Inc, New York, 2001.