Clinker‐efficient cements and their application ‐ today and tomorrow

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.