PULL-OUT BEHAVIOUR OF STEEL FIBRES IN SELF-COMPACTING CONCRETE

摘要

Self-Compacting Concrete(SCC)is an upcoming building material which is characterized by many favourable hardened and fresh concrete properties.However,like all concretes,also SCC has the disadvantages of a low tensile strength and a large brittleness.To improve the tensile strength,the ductility and the toughness it is useful to reinforce the concrete with steel,glass or synthetic fibres.In practice,the often favoured steel fibres are available in a very wide variety regarding characteristics like strength,size,shape and surface properties.Until today there is an insufficient knowledge about the influence of the mentioned fibre characteristics on the hardened properties of steel fibre reinforced self-compacting concrete(SFRSCC).For this reason a research program was started,focused on the pull-out behaviour of different types of steel fibres in SCC.Within the experimental investigations a SCC and in comparison a normal vibrated concrete,both with a compressive strength of approximately 65 N/mm2,in combination with two different steel fibres were used.The influences of the fibre end hook,the embedment depth and the concrete age on the pull-out behaviour of the fibres were determined.The results of the investigations can be summarized as follows: For fibres with end hooks the concrete age and the embedment length are negligible parameters.The load transfer from the fibre to the matrix is almost completely realized by the end hooks.Furthermore,it is to note that the scattering of the force-displacement curves is relatively high.Hence,a high number of pull-out tests were necessary to get clear tendencies.By the interpretation of the test results a better choice of a suitable fibre type regarding the application conditions is possible.The main consequence is a better and faster development of steel fibre reinforced self-compacting concrete mix designs for utilization in practice.