Creep Behaviour of Cracked High Performance Fibre Reinforced Concrete Beams Under Flexural Load

Abstract

The investigation on flexural creep of high performance fibre reinforced concrete (HPFRC) is still scarce. Even though the presence of fibres in concrete help to control the deformations, these may increase under the effect of a sustained load. To analyse the effect of creep in pre-cracked HPFRC elements, twelve beams reinforced with either glass or steel fibres with dimensions 40 x 80 x 1200 mm were tested under a three-point configuration. For that, a new type of frame was designed and constructed to test the HPFRC beams under flexural load in a climate-controlled room with constant temperature and relative humidity. The loading mechanism was based on a lever system, applying sustained load ranging between 25% and 50% of the load at which the first crack appeared. The deflection at the mid-span was registered by means of LVDT transducers. Additionally, the influence of the curing procedure (with or without aluminium tape wrap) was assessed. In general, glass fibre reinforced beams presented higher deflections than steel fibres, even though at low load levels the type of fibre did not have significant influence on the deformation.

Improvements in test methodology and characterisation of long-term flexure behaviour of fibre-reinforced concrete

“…Although most of experimental programmes of structural elements (74%) were focused in FRC structural beams [121,125,131,136,141,149,115], experimental tests carried out on suspended slabs [143,148] slabs-on-grade [70], and FRC pipes [145][146][152][153] were also reported. Regarding creep tests on beams, a wide range of beam dimensions were reported from 1.2 to 4.0 m in length.…”

“…addition, the pre-cracking test flexure setup corresponds, in most cases, to the flexure setup used in creep tests, where only a few studies [127][128][129][130][131][132][133]149] reported a different flexure setup in pre-cracking tests than used in long-term tests. Due to the absence of a notch in most procedures to localise crack propagation and specific pre-cracking procedures, deflection is the most registered deformation to assess long-term performance on structural elements, as seen in Figure 26.…”

“…The most studied variable is the creep index, reported on 65% of the experimental programmes, as seen in Figure 30. Some studies [149] assess load level influence by loading identical beams at different load levels, whereas other publications [142,147,154] reported studies where the sustained load was increased in load-level steps during the creep test duration. Fibre type and pre-crack level variables, with 39% and 35%, respectively, are also quite reported.…”