Clinker-efficient cements and their application - today and tomorrow

Abstract

The concrete standard DIN 1045-2 currently provides fixed limit formulations for the respective exposure class. The tests of cements in concrete with regard to durability (carbonation, chloride penetration, frost and freeze-thaw salt resistance) are now carried out within approvals procedures in a limit composition for the exposure class under consideration. Test results of clinker-efficient cements are shown against the assessment background of the German Institute for Building Technology (DIBt) e. g. for carbonation: This test is currently to be carried out with a water-cement ratio of w/c = 0.50. While, for example, a CEM III/A or a CEM II/C-M (S-LL) fit well into the assessment background in this test with the required limit composition, the depth of carbonation of a cement is 20 percent clinker, 30 percent blast furnace slag and 50 percent unburned limestone clearly outside. If the water-cement ratio is reduced to w/c = 0.40, the result is already in the upper range of the evaluation background. A further reduction to w/c = 0.35 leads to a result in the range of the reference cements. A further significant reduction in the clinker content in cements with a high proportion of unburnt limestone would therefore be possible if the concretes are composed accordingly.