Time-dependant behaviour of engineered cement-based composites

[摘要] ECC (Engineered Cement-based Composites) is a type of HPC (High PerformanceConcrete) that was engineered to overcome the weaknesses of ordinary concrete. Itshows high ductility as it can resist the full tensile load at a strain of more than 3 %.This superior response is achieved with multiple cracking under tensile loading whichhas a pseudo strain hardening phenomenon as result.The purpose of the research project reported in this dissertation is to investigateand characterise the time-dependant behaviour of ECC and create a constitutive modelto numerically simulate the static and time-dependant behaviour of ECC.To investigate the time-dependant behaviour experimentally, rate and creep testswere done on the meso- and macro-level while rate tests were done on the structurallevel.The meso-level was represented by the pull-out testing of fibres embedded inthe cement-based matrix and direct tensile tests were done for the macro-level.Flexural tests on thin beams were done to simulate the structural-level.Strong time-dependant behaviour was found on all three these levels. On themeso-level, the most prominent finding is that the failure mechanism can change witha change of strain rate, i.e. fibre pull-out at a low pull-out rate, while with a high pulloutrate, fibre rupture can occur. Even though the strength of a tensile specimen onthe macro-level showed a dependence on the strain rate, the ductility remainedconstant over four orders of magnitude of the strain rate. On the structural-level,however, a reduction of the flexural ductility was found with an increase of the ...

[发布机构] Stellenbosch University