Strain development of traditional and self-compacting concrete during fire

In this paper a complete strain model is derived that describes the strains developed during fire (till 400 degrees C) and is based on the model of Anderberg, published in 1976. This model describes the total measured deformation as a superposition of 4 strain types: free thermal strain, instantaneous stress-related strain, creep strain and transient strain. The strains are derived from experimental loading tests on cylinders with dimensions empty set106x320mm, submitted to load ratios of 0, 20 and 30% of the initial strength before heating. The instantaneous stress-related strain should be derived from a loading test till failure at high temperature. However, to avoid damage to the furnace, this strain is assumed to be in the same order of magnitude as for cylinders tested for Young's modulus immediately after cooling. The parameter k(2) used to model the transient strain according to Anderberg is in this paper found to have a non-linear relationship with temperature, instead of linear as originally proposed by Anderberg. All tests occurred at a heating rate of 5 degrees C/min and the specimens were pre-dried to avoid explosive spalling. The investigated concretes are a traditional and self-compacting concrete with a testing age of about 30 months. Only small differences between both types are found for the transient strain