The history of binders: from caementicium to cement

Pantheon in rome

The first hydraulically hardening mortars were used as early as 1000 B.C. by Phoenician builders who mixed burnt lime with ground clay bricks or volcanic ashes (pozzolans). The term “cement” originates with the Romans who, as of the third century B.C., constructed buildings from a mixture of quarried stones, pozzolan and clay-brick meal and burnt lime, thus developing an early form of concrete constructions. The span of the Pantheon’s dome in Rome, erected in 120 A.D., already measured an impressive 43 m and was not outmatched until 1911 with the construction of the Centennial Hall in Wrocław, a modern concrete shell structure.

Binding agents displaying hydraulic properties through the addition of pozzolans were used until well into the 19th century. During the Middle Ages and Early Modern History, materials science remained an artisan’s discipline. Nonetheless, audacious stone edifices were built that bear testimony to the skill of the times’ master builders and that exploit the maximum strength of the materials used. Thanks to the precision with which the stone blocks were worked and the resulting thinness of the mortar gaps, no stringent requirements were placed on the binding agents is use at the time.

It was not until progress in the field of iron- and steelworking, which facilitated employment of this new material for components subject to torsional and pressure loads, that rationalisation of solid construction techniques became necessary. From the development of quarry stone masonry with mortar gaps to Roman concrete, this process eventually lead to modern concrete. At the same time, the development of hydraulic binding agents was advanced and their water resistance, setting progression and final strength was continuously improved. Even today, development of innovative types of cement and concrete continues unabated.

Development history of hydraulically setting binders

The essential feature of hydraulically setting lime, the addition of clay before burning, was discovered in the mid-18th century by the Englishman J. Smeaton. Based on his findings, the French L.J. Vicat and H.V. Collet-Descotils as well as the German J.F. John contributed significantly to research on the hydraulic properties of binders in the early 19th century.

In 1796, the British J. Parker obtained a patent on a fired hydraulic binder made of lime marl with a high content of clay which he christened “Roman Cement”. In reality, based on the composition of resources and a firing temperature below the sintering limit, the product was actually a hydraulic lime. The hydraulic binder developed by the English bricklayer and builder J. Aspdin and patented in 1824 under the name “Portland Cement” was also not yet a cement in modern terms.

It was not until the 1940s that, as part of factory production, the raw mix was fired at temperatures reaching the sintering limit, thus achieving a mineralogical composition approaching that of modern-day cements. It was particularly the work of the German W. Michaelis during the late 19th century that lead to the first quantitative specifications for composition of the raw mix used in production of Portland cement. The French H. Le Chatelier and the Swede A.E. Törnebohm are credited with the description of Portland cement clinker as a multi-phase microstructure consisting of different minerals, the proportions of which vary within certain limits. During the early 20th century, this findings formed the basis for further research, such as conducted by the head of the Berlin cement laboratory, H. Kühl.

Modern cements and concrete construction methods

With the availability of a hydraulic binder that achieved high strength and excellent durability, it became possible to substitute quarried stone masonry, which entailed a massive workload, with the construction material concrete. Reinforcing the concrete using iron elements then also facilitated production of building components made of concrete that were capable of taking up torsional and tensile loads. The patent obtained in 1867 by Monier on the manufacture of wire-reinforced cement plant pots is generally regarded as the birth of ferroconcrete construction. However, reinforced cement components had previously already been produced. Lambot, for example, produced an armoured concrete ship for the 1854 World Exhibition.

The advantages of composite reinforced concrete in respect to fire, corrosion and mechanical loads quickly led to the young material’s breakthrough. In bridge construction, slim designs became possible that by far outdid the arched stone bridges in terms of audacity. The pioneers of reinforced concrete construction included the engineers Wayss, Freyssinet, von Emperger and Mörsch. With the system named for him, François Hennebique developed a flexible construction structure that also inspired architects to use concrete for slender components and for spanning wider expanses. The material was used mainly in heavy-duty construction until Le Corbusier’s Domino House (1914) and Mies van der Rohe’s legendary concept for an office building (1922) reclaimed concrete as a material for architecture.

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