DECORATIVE CONCRETE 

Concrete Knowledge Part 3~

Advancements in Concrete

16th-century improvements

A bricklayer in Andernach, Germany, tried mixing volcanic ash called trass with lime mortar. The resulting material was water-resistant and strong — and the chain reaction started by the discovery would lead to the creation of modern cement.

17th-century concrete trade

In the 17th century, the Dutch (who were already adept at building in water) sold trass to France and Britain for use on buildings that required waterproof properties. The two rival countries immediately began competing to create their own hydraulic building materials.

* 1793 – Modern production of hydraulic lime for cement

When British civil engineer John Smeaton was commissioned to build a new lighthouse on the Eddystone Rocks in Cornwall, England, he set about searching for the most durable and waterproof building material he could find. After finding limestone nearby with a high concentration of clay, he fired it in a kiln and turned it into clinker. He ground it into powder and mixed it with water to create a paste, with which he built the lighthouse.

In the process — and more than 1,000 years after the secrets of concrete were lost — Smeaton rediscovered how to make cement. Before long, manufacturers started marketing his discovery as “Roman cement.” And the Eddystone Lighthouse stood for nearly 130 years, outlasting the rocks that eroded out from under it.

* 1824 – Invention of Portland Cement 

Englishman Joseph Aspdin refined the process by carefully proportioning limestone chalk with clay and burning the mixture in a kiln until the carbon dioxide was removed. He also heated alumina and silica until the materials became glass-like, then pulverized them and added them into the limestone mixture along with gypsum.

The resulting chemical combination of calcium, silicon, aluminum, iron, gypsum, and other mineral ingredients makes up the distinct formula for Portland cement, the basic ingredient of concrete. Aspdin named the result “Portland” cement because it resembled the high-quality building stones quarried in nearby Portland, England.

* 1836 – Strength testing

The first testing of concrete’s tensile and compressive strength took place in Germany. Tensile strength is the ability to resist tension or pulling apart; compressive strength is the ability to resist compression, or pushing together.

* 1850s – Reinforcement with steel mesh patented

A French gardener, Joseph Monier, experimented successfully with pouring concrete over a steel mesh. (Concrete and steel expand at a similar rate when they heat up, making them a perfect pairing). Monier patented several variants of his invention for use with railway sleeper cars, building slabs, and pipes. Reinforced concrete is much stronger and more practical than the unreinforced stuff. It can span larger gaps, allowing concrete to soar in the form of bridges and skyscrapers.

* 1880s – Reinforcement with iron bars 

California engineer Ernest Ransome began testing concrete and 2-inch iron rods to see if the materials would bond. When they did, Ransome went a step further by twisting the iron bars to create an armature around which he could “build” concrete into any desired shape — an experiment which also worked. Today we call this system reinforcing bar, or rebar, although modern engineers typically use steel instead of iron.

Ransome’s system soon would be used in commercial buildings, roads, bridges, and even the first skyscrapers. Famed architect Frank Lloyd Wright began to implement rebar concrete technology in modern architecture. Some of Wright’s most famous buildings — including Unity Temple in Oak Park, Illinois, considered the world’s first modern building; and Fallingwater in Mill Run, Pennsylvania, his most celebrated work — were made of reinforced concrete.

* 1880s – Prestressing steel patented

The process of prestressing steel was patented to make concrete stronger and allow engineers to use less steel and concrete.