"The father of the cement chemistry"

Le Chatelier brought to the cement industry a hand of unusual experimental skill, a brain of marvellous perception and a spirit of achievement that placed him at the front of all his contemporaries.

RG BLEZARD 

Two years after his death, his achievements were publicly honoured by Dr R H Bogue at the Second Symposium on the Chemistry of Cements at Stockholm in 1938.

Extract of Bogue's speech

Cement chemists cannot gather and discuss the problems of cement chemistry without thinking of the man whom we have come lovingly to recognize as the Father of cement chemistry, Henry Le Chatelier, formerly of the Sorbonne. Physical chemists generally think of him as one of the great savants of physical chemistry and know him best for his contributions to thermodynamics, particularly, perhaps, for the law that has come to be known as the principle of Le Chatelier. But cement chemists think of him for other reasons. His works on the chemistry of Portland cement are of fundamental importance. Through microscopical and chemical studies he has demonstrated that clinker contains a number of different minerals of which tricalcium silicate is the bearer of hydraulic properties. He has also demonstrated that gypsum, calcium aluminates and Portland cement attain their set through a crystallization process from supersaturated solutions. He was one of those men who believe that :

"we cannot intelligently control industrial processes until we know the nature of the things with which we are dealing"

Pioneer of the use of the optical microscope on clinker Portland

Le Chatelier published in 1882, in the Comptes-Rendus de l'Académie des Sciences, for first time the description of the four main phases of the clinker.

The illustrations of his observations are published in the Annales des Mines in 1887.

The success of 1887 was the presentation of Henry Le Chatelier’s classic doctoral thesis "Constitutions des ciments hydrauliques".

A microscopic analysis of thin sections of cement clinkers allowed Le Chatelier to observe four different kinds of crystals, which were later named by Alfred Elis T?rnebohm (1838-1911) alite, belite, celite (brown), and felite. In well-burnt clinker celite formed the filling material and magma from which the alite had separated. Le Chatelier made the interesting observations that the grappiers, or hard nodular masses which resisted slaking, yielded a cement, which when ground, consisted almost entirely of alite.

All this information allowed Le Chatelier to develop a theory applicable to the setting of all hydraulic cements. In contact with water, a supersaturated solution was formed which deposited a less soluble hydrated material; this constant solution and deposition of material resulted in the production of an interlaced and coherent mass of minute crystals.

By the shrewd use of Henri Clifton Sorby’s microscopic petrographic methods he found that all cements contained a common constituent, 3CaO×SiO2, whose composition he established. His earliest paper postulated the Orthosilicate 2Ca0.Si02 as the main and only hydraulic constituent of Portland cement. But in 1887 he stated that tricalcium silicate was the main constituent it did not meet with general acceptance, because many investigators considered alite as a solid solution of calcium aluminates and silicates. The Le Chatelier view was confirmed by Shepherd and Rankin (1911), by Rankin and Wright (1915)

How Le Chatelier started its path in the cement world?

Vicat, his grandfather’s friend, had done his research on synthetic hydraulic cements at the école des Mines and left there a large set of samples. He had become acquainted with cements in his grandfather home and learned the theory of the Portlands. This led Le Chatelier to look into the subject and to find that very little had been published on the constitution of this class of materials.

The Le Chatelier approach of Theory and Practical applications

His choice of research projects clearly reflects his appreciation of the interplay between theoretical science and its practical applications. Indeed, he consistently chose research problems of wide interest which seemed to give promise of industrial applications.

His very first area of investigation, for example, brought him into the largely uncharted area of the chemistry of cements.

He began by repeating the experiments of Lavoisier and Payen on the preparation of plaster of Paris. He discovered that good plaster of Paris consists of the hemihydrate of calcium sulfate, which he identified, and not of the anhydride as was previously believed. These investigations led him to a theory applicable to the setting of many kinds of cements.

Part of Le Chatelier's work was devoted to industry. For example, from 1897 to 1932, he was a consulting engineer for a cement company, the Société des chaux et ciments Pavin de Lafarge, later known as Lafarge Cement, actually LafargeHolcim.

Development of the "platinum-platinum-rhodium Thermo couple"

His studies with cements also give evidence for the extraordinary practical skill with which Le Chatelier selected, modified, or in some cases actually invented the instruments needed to carry on his researches. In his work with cements, for example, he chose a method of thermal analysis devised by Regnault but little known at the time. Methods known at the time for determining high temperatures, such as the use of gas thermometers and of thermocouples, soon proved inaccurate for Le Chatelier's work with cements. The determination of high temperatures soon became a routine procedure following the development of the platinum-platinum-rhodium Thermo couple.

Development of the "Hydraulic Module Concept"

Le Chatelier also concluded that there must be an upper limit to the content of calcium oxide, corresponding to the formation of triacalcium silicates and aluminate. An excess of this compound results in expansion and disintegration on setting. Insufficient lime would lead to the formation of the bicalcium silicate, unable to hydrate. Although the theoretical limit is three moles of calcium oxide per mole of acid elements, the practical limit is about 2.5 because actual fusion does not occur in the kiln and the reactions do not go to completion. The limit fixed by Le Chatelier constitutes the first theoretical hydraulic modulus and has developed into other modules depending on the specification for the cement (1887).

Determination of Soundness of cement by Le Chatelier Method

The Le Chatelier apparatus, consists of a small brass cylinder split along its generatrix. Two indicators with pointed ends are attached to the cylinder on either side of the split; in this manner, the widening of the split, caused by the expansion of cement, is greatly magnified and can easily be measured. The Le Chatelier test detects unsoundness due to free lime only.

Specific Gravity Test Procedure for Cement

One can easily determine the value of specific gravity of cement using Le Chatelier Flask method. Determination of specific gravity of cement at the site level can be easily done using this is an experiment

Le Chatelier Experiment, the question waiting for an answer

In 1904, Le Chatelier undertook the first scientific study of Portland Cement Hydration, with the very few scientific instruments available at his time. He observed at ambient temperature, two cement pastes, one hydrating in air and a second one under water.

His conclusions were very simple: during hydration, a cement paste develops an 8% contraction of its absolute volume depending of its mode of curing. If the paste is cured in air, it shrinks; if it is cured under water, it swells.

Humbly, Le Chatelier admitted that he was unable to explain why the paste cured under water was swelling and breaking the glass container after a while. It must be admitted that 100 years later, there is not yet a clear explanation for such behaviour.

Le Chatelier returned on several occasions to the study of cement, concerning himself especially with the improvement of methods of analysis and testing, with the control of manufacture, and with the conditions bringing about the disruption of masses of cement and concrete in air, water, or seawater.

Honors and Recognitions

Le Chatelier received many honors for his contribution to science and industry.:

• He was made Chevalier de la Legion d’Honneur in 1887, promoted to Officier in 1908, Commandeur in 1919.
• Le Chatelier was six times candidate to the Académie des Sciences (1894, 1897, 1898, 1899, 1900, and 1907). He was finally elected member on 1907
• He became a foreign member of the Royal Society in 1913 and received the Davy Medal in 1916.

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