Analysis of some basic creep tests on concrete and their implications for modeling

The basic creep of concrete is the delayed deformation that occurs when concrete is subjected to loading without drying. This paper analyzes some findings from the literature. The derivatives of the compliance function J of basic creep tests with different loading ages t0 are compared. It has been observed that when dJ/dt is considered as a function of time t, the long-term behavior is logarithmic with a uniform slope. This indicates that basic creep could be expressed as a logarithmic function in which the age of loading does not affect the final slope. In the recent fib Model Code 2010 (MC2010), basic creep is expressed exactly in this way. Using experimental data, the parameters of the model are calculated for each test and compared with the values proposed by MC2010. It is shown that MC2010 gives a fairly good set of values for the parameters whose accuracy could nevertheless be improved by adjusting these parameters to match experimental result