Prelirnimwy remarks In rev iewing progress in this field for the 8th international Congress on the Chemistry of cements the aut11ors are again conscious that full just ice can- not be done to all the publications that have appeared in the last six year s.A selective review has been cho- sen in preference to a purely bibliographical approach The basis for selection has involved the inter play of several criteria: a desire to maximise the international content (papers from mor e than 20 countries are included) priority given to papers concerned with chemical aspects. condensation of multiple publications on the same topic by the the same or closely' associated r e- search groups. emphasis given to divergent views expressed on a given subject the pragmatic implicat ions of both predominantly se ienti f ic contributions and those of a primare ly empirical natur e. In this manner the following review has been restric- ted to sorne 300 publications.The authors extend their sincer e apologies to. al l those work has not been men- tioned. definitions: special cements are binders used for specific appli- cations ,requiring materials whose characteristics are outside the limits standardised for portland cement or manufactur ed rrom raw material ,by means of process differents from those of port land cement. Ttds proposed definition, based on preparation and use of cement is r est r ictive ,because lt does not take Into account the fact that lt Is possible to obtain special properties with ordinary Portland cement, by using admixtures ,or by spec ial treatment (autoclavlng ....... .On the other hand ,a def lni t ion based on the fundamen- tal concept or the nature or liaison developed by the binders to Insure its cohesion or Its adhesion to aggre- gate s does not allow a conclusive distinction because such types or hydraulic bond can lead to a special or a conventional cement. This Is the reason why , In spite of its weakness ,we shall use this definition at least as starting point or our paper. The special cements present a scientific and Indus- trial interest: the Increase of the knowledge of Portland cement obtained during half of a century leads to an Increase of the difficulties of research In this field and requires more and more complicated experimental procedures .The study of new systems of binder could allow a better understanding of the mechanism or the conventional cements. lndustrially,the production or Portland cement Is increasing In the low GNP countries and decreasing in the high GNP countr ies where conversely the produc- tion of special cements is increasing. Consequently there exists in these countries an increasing interest to Invest in high added value binders used for applica- tions different from construction.
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