El módulo de elasticidad del hormigón de alta resistencia

The modulus of elasticity of high strength concrete

A wide research programme has been carried out about High Strength Concretes in the Laboratorio Central de Estructuras y Materiales, del CEDEX, including different aspects of the technology of concrete and its mechanical properties. Concretes with strengths between 20 and 120 MPa have been tested. One of the aspects analyzed has been the modulus of elasticity, because of its influence on structural strains. The study has shown the importance of the aggregate on this property of concrete. Some European Codes introduce a parameter contemplating this effect in the formulae, like Model Code or BS8110. Different suitable aggregates for concrete can be found in nature. which introduce differences until 100% in the modulus. Although these extreme cases are not usual with normal aggregates, differences of 30% are easy to find, origined only by the aggregate used. In fact, this has been shown during the research programme. The formula proposed in EH-91 (Spanish Code), does not introduce any parameter related with the aggrecate, althoug in some cases the effect can be more relevant even that othes contemplated as the age or the strength of concrete. Besides, the values given by this formula are much higher than those obtained in the tests, and the more the higher the strength of concrete. Accorfing to the tests, the formula of Model Code gives the best adjustment to the experimental results. Using data from other aggregates not included in this Code, this formula has been completed.