The behaviour of the trace elements is important for the effects of the use of secondary materials on the environmental compatibility of the product. Cements exclusively produced from natural raw materials and fuels show, due to the storage conditions, a broader range in the concentration of trace elements. If secondary materials are used, then the trace element contents in the cement can rise or fall. The use of suitable secondary materials which give rise to contents of trace elements which lie within the range of previous experience, has no effect on the environmental compatibility of the cement. All kinds of cements have been used for decades in building and the environmental compatibility of the cement is unquestionable. It is not the absolute trace element contents (potential) which are important for the evaluation of the environmental compatibility of cements, but the proportion available under the conditions of use at the time which must be considered. Building materials bound together with cement have the property of chemically binding trace elements and at the same time encapsulating them physically. Thus even cements having relatively high trace element contents (beyond the present range of experience) have low release values (elution values). In recent years a number of elution processes have been developed which allow the realistic evaluation of cement-bound building materials, under their actual conditions of use, with respect to possible effects on the environment. In such testing, even under extreme conditions, no release of trace elements relevant to the environment was observed. However, until now there has been no success in agreeing on uniform test conditions. Furthermore it is necessary to establish maximum and minimum limits against which the laboratory results can be measured for the evaluation of the environmental compatibility of the product. The use of secondary materials has no detrimental effects, from the point of view of health protection, for cement users or for the use of cement-bound building materials.
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