Experimental Study on the Influence of the Shape and the Size of the Specimen on Compression Behaviour of High Strength Concrete
In this paper we investigate the mechanical behavior of high-strength concrete (around 100 MPa) in compression and tested in strain-control. We are particularly interested in the influence of the shape and the size of the specimens on the compressive strength, fc, of the material. In a previous study  we managed to get ductile compressive tests by using small cylinders and by controlling the strain instead of the load. The experiments were tested at four strain rates since the purpose of the research was to check the sensitivity of the whole stress-strain curve to the speed at which the specimen is loaded. Here we address the problem of the effects of the size and the shape of the specimens on their mechanical behavior. We use cylinders and cubes of different sizes: the dimensions of the cylinders are 75 x 150, 100 x 200 and 150 x 300 mm (diameter x height); the edges of the cubes are 33, 50, 66 and 100 mm long. The plane sides of the cylinders and all the cubes were polished to avoid local imperfections and to minimize friction against the loading platens. The standard properties of the material are given in Table 1. By ‘standard’ we mean properties obtained according to well-established procedures, i.e., procedures devised for normal strength concrete. Please, notice that the characteristic length, lch, of this concrete is roughly 150 mm, closely half the lch of normal concrete. This means that, from a Fracture Mechanics standpoint, we expect that high-strength concrete (HSC) is more brittle than NSC for the same specimen size [1, 2, 3, 4].
KeywordsCompressive Strength Dense Columnar Normal Concrete Normal Strength Concrete Small Cylinder
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