Cover Image
close this bookBASIN - News No. 03 - January 1992 - Building Advisory Service (BASIN-GTZ-SKAT, 1992, 34 p.)
close this folderRoof as section
View the document(introduction...)
View the documentFCR/MCR Tile production as a business
View the documentLetters to the editor
View the documentEarth as section
View the documentWhy it is essential to establish norms for compressed earth blocks
View the documentExamples of technical specifications for performance classes

Examples of technical specifications for performance classes

Compressive strenght performances CEB

Technical specifications for CEBs are often limited to giving only a wet compressive strength value. This type of specification often proves fairly unrealistic in practice, as it presupposes a costly laboratory test. In addition, correctly undertaken, the test takes sometime. Moreover, unstabilized blocks cannot generally give sufficiently high performances when wet. While retaining the compressive strength test, one can, however, introduce certain elements which will make the technical specification more realistic. In the first place, a distinction should be made between two class levels, those which use only a dry strength test (for unstabilized blocks) and those which use both a dry and a wet strength test (for stabilized blocks). This differentiation already allows all blocks, even those produced by craft workshops, to be evaluated. In the next place, it is essential to describe the testing method used, as this has a major impact on the results recorded. Comparing blocks tested using different testing methods makes no sense at all. Finally, a simplified testing method might be used for classes 1 and 2. These simplified methods will undoubtedly in general be less precise in absolute terms, but also less costly and therefore better suited to workshop production conditions.

technical characteristics CEB

Even a simplified compressive strength test, however, requires a minimum investment in materials and sufficiently skilled personnel. In the absence of all optimum conditions coming together, one often ends up with tests which are of little scientific value. Tests which are a great deal simpler, but which it is much easier to carry out rigourously, might then tee suggested. Compressive strength is above all an indication of a certain manufacturing quality and of probable durability. One can suggest technical specifications which use indicators other than quality and durability, i.e. dry density and bending strength. There is in fact a fairly high correlation between these characteristics and compressive strength. This means that one can use a multi-class system based on these characteristics. From the economic and practical point of view, this will give a more realistic method for assessing the average level of production making a distinction between craft workshop conditions and industrial production.