Prova për vetitë termike dhe klimaterike të agregateve -Pjesa 4 : Përcaktimi i tkurrjes nga tharja

Tests for thermal and weathering properties of aggregates - Part 4: Determination of drying shrinkage

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This standard describes the reference method used for type testing and in cases of dispute, for determining the effect of aggregates on the drying shrinkage of concrete. For other purposes, in particular factory production control, other methods may be used provided an appropriate working relationship with the reference method has been established. This standard is based on the testing of concretes of fixed mix proportions and aggregates of 20 mm maximum size. NOTE 1 Guidance on the use of larger size is given in Annex A. Precision data is not available for variations in size and for variations in the water content of the test concrete. NOTE 2 In those cases where the drying shrinkage of a source of coarse aggregate only or a source of fine aggregate (sand) only are required, the other component to be used should be, respectively, a fine or coarse aggregate of known low shrinkage. NOTE 3 Aggregates with high water demand and/or porosity may in a concrete with a fixed water content result in a mix with insufficient workability to allow full compaction of the test specimens. This is likely to occur with aggregates combinations having a composite water absorption value greater than 3,5% or oven-dried particle densities less than 2,45 Mg/m³ (e.g. for recycled aggregates). In such instances a variation of the method (without precision data) may be carried out by one of the following changes to the concrete mix: (a) use of aggregates in the saturated and surface dry condition. (b) use of water-reducing admixture. A note on the details of any modification to the mix design should be included with the test report.