Design and verification of a testing system for strength, modulus, and creep of concrete subject to tension under controlled temperature and humidity conditions

• A device is developed to measure mechanical properties under direct tension.
• The experimental data are verified with these obtained by other well-established testing methods.
• The modified B3 model was found fit the early-age tensile creep well.
• The retardation spectrum was determined for numerical computation.

Investigation on concrete creep under direct tension often encounters experimental difficulties. This paper describes a testing system contrived to perform the tensile strength test, elastic modulus tests and the creep tests subject to direct tension under controllable temperature and relative humidity conditions. The results are analyzed to determine their reliability. The tensile strength and modulus are compared with those obtained from indirect tensile test methods and the estimation from the code equations. Different creep predictive models are used to verify the validity of the early age tensile creep data. The basic creep data are curved fitted with modified B3 model and are characterized using Dirichlet series. Also the retardation spectrum, which presents the parameters’ information of the physical model, is plotted. The data generated by this testing system had proved that the system is capable and reliable for repeated performance.