The Portland cement industry consumes large amounts of energy and produces huge quantities of carbon dioxide, which contribute to global warming, the so-called “Greenhouse Effect”. Industrial trials are reported for the production of belite cements (≈3000 t) at lower temperatures and with lower lime saturation factors than for ordinary Portland cement. Belite cements with reasonably good properties have been made on an industrial scale from limestone, burnt clay, volcanic ash, pyrite ash and gypsum. A rapid rate of cooling improves the hydraulic activity, and also the physical–mechanical properties by stabilising reactive forms of belite. Such low energy cements provide a cheap alternative to Portland cement with properties that are acceptable for many applications and the additional benefit of possible improved durability.

Thermal studies, sometimes together with X-ray analysis, were applied to investigate the process of hydration in the systems calcium silicates (tricalcium silicate or dicalcium silicate) - water - electrolyte. Alkali metal or alkaline-earth metal salts were used as electrolytes. Results and conclusions are presented concerning the action of electrolytes upon the kinetics of hardening of the calcium silicates and the composition and phase transformation of calcium hydrosilicate in the presence of low proportions of electrolytes (0.5, 2 and 5 mass%), these effects being due to ionic substitution. A higher proportion of electrolyte (above 2%) in the systems calcium silicate-water can determine the formation of a complex salt, e.g. calcium hydroxysalts or double hydrosilicates.

In the present paper the possibility was studied of the hydration activation for high aluminous cements, which have relatively high Al2O3/CaO molar ratio, with the purpose to maintain good binding properties. Calcium sulphate aluminate (<C(4)A(3)(S)over bar>)* was used as an activator of the binding properties of these aluminous cements. In this way, as a result of a drastic reduction of their calcium oxide content, very good thermomechanical properties of the aluminous concretes can be obtained.

The behaviour of the aluminosilicate vitreous-crystalline binder systems based on the cementitious (slag) and hydraulic active admixtures (fly ashes) with alkaline activators was examined. The experimental results support the conceptions concerning the mechanism and the chemical-structural bases, respectively regarding the activated hardening of the above-mentioned binder systems.

The possibility to prepare expensive sulphate aluminate masses from certain wastes (phosphogypsum and belitic waste) and usual raw materials (limestone, bauxite) has been investigated. The chemical and minerological composition of these synthetic clinkers as well as the nature of their hydration products has been determined by current methods. The mechanism of cement expansion and the factors affecting the correlation between mechanical strength and expansion have been also studied.

ON ETUDIE LA CINETIQUE DES PROCESSUS D'HYDRATATION ET D'HYDROLYSE DES SILICATES DE CALCIUM DU CLINKER DE CIMENT PORLTAND. ON ETABLIT LES EQUATIONS ET L'ON TIRE DES CONCLUSIONS SUR LE MECANISME DES PROCESSUS. L'INFLUENCE DES CHLORURES ALCALINS ET ALCALINO-TERREUX, DE MEME QUE CELLE DE CERTAINS SELS DE CALCIUM, SUR LA CINETIQUE DE CES PROCESSUS EST EXAMINEE. ON ETABLIT DES CORRELATIONS ENTRE L'ACTION DES ELECTROLYTES ET LEUR NATURE.