Cement history

Precisely when master builders began using binders in construction cannot be ascertained, but traces of lime mortar have been found in structures in Turkey that are over 14,000 years old. In the high cultures of Mesopotamia (before 2000 B.C.) and Egypt, builders used burned lime. The Egyptians used it as a binder to construct the pyramids (before 2600 B.C.). We know that the Phoenicians (before 1000 B.C.) mixed their mortars with ground volcanic rock or ground brick, thereby producing binders that could set even underwater. Greek colonies in southern Italy dating from about 150 B.C. feature masonry walls that consist of two neatly laid faces and the interstitial cavity filled with a mix of mortar and rubble or stones, called emplekton.

The Romans developed the technology further. They were the first to use concrete, constructing with it foundations, building components, aqueducts, and quay walls. Their opus caementitium, from which our current word "cement" is derived, was of such high quality that structures built with it still exist today. Large parts of the Colosseum in Rome are made of Roman concrete. Another famous example of Roman concrete architecture is the Pantheon in Rome, which was begun in 27 B.C. Its concrete dome with a diameter of 43 meters was outdone only by steel-reinforced structures, for example, Century Hall in Breslau, with a clear span of 65 meters, built by Max Berg in 1912.

The constituents of opus caementitium, Roman concrete, are burned lime, water, sand, and broken stone. Roman master builders also mixed pozzolan and ground brick into their concrete, thereby producing a building material that also hardened and remained firm underwater. Lime burners, or magister calcariarum, burned lime at about 1000°C. Pozzolan is a type of natural stone, mainly volcanic ash.

The knowledge of opus caementitium was lost with the fall of the Roman Empire. In many cities the predominant construction technique was half-timbering infilled with wicker or wattle and daub. For the construction of masonry buildings, builders chiefly used air-hardening lime mortars such as loam-lime-sand mortar or loam-lime mortar. These mortars are not water resistant and are not particularly durable. Some foundations were made of mortar containing ground brick.

In 1824, Englishman Joseph Aspdin burned a blend of lime and alumina. Using this binder he produced artificial stone that matched the color of the often-used limestone from the Portland peninsula on the English Channel. He therefore named his product Portland cement. This binder was also not yet a cement by current standards; as the firing temperature had not yet reached the sintering point of about 1450°C. This was first achieved by his son William, at the newly established factory for Portland cements. During the construction of the Parliament building in London, builders ascertained that the binder from this factory was superior to Roman cement. Isaac Charles Johnson first recognized the importance of burning at high temperatures in 1844.

In 1862, E. Langen in Germany discovered that the strength and sulfate resistance of cement could be enhanced by the addition of blast-furnace slag that had been rapidly cooled and substantially glassified.