This paper deals with the coupled effect of temperature and silica fume addition on rheological, mechanical behaviour and porosity of grouts based on CEMI 42.5R, proportioned with a polycarboxylatebased high range water reducer. Preliminary tests were conducted to focus on the grout best able to fill a fibrous network since the goal of this study was to develop an optimized grout able to be injected in a mat of steel fibers for concrete strengthening.The grout composition was developed based on criteria for fresh state and hardened state properties. For a CEMI 42.5R based grout different high range water reducer dosages (0%, 0.2%, 0.4%, 0.5%, 0.7%) and silica fume (SF) dosages (0%, 2%, 4%) were tested (as replacement of cement by mass). Rheological measurements were used to investigate the effect of polycarboxylates (PCEs) and SF dosage on grout properties, particularly its workability loss, as the mix was to be injected in a matrix of steel fibers for concrete jacketing. The workability behaviour was characterized by the rheological parameters yield stress and plastic viscosity (for different grout temperatures and resting times), as well as the procedures of mini slump cone and funnel flow time. Then, further development focused only on the best grout compositions. The cement substitution by 2% of SF exhibited the best overall behaviour and was considered as the most promising compared to the others compositions tested. Concerning the fresh state analysis, a significant workability loss was detected if grout temperature increased above 35 degrees C. Below this temperature the grout presented a self-levelling behaviour and a life time equal to 45 min. In the hardened state, silica fumes increased not only the grout's porosity but also the grout's compressive strength at later ages, since the pozzolanic contribution to the compressive strength does not occur until 28 d and beyond. (C)
Test setups and loading histories aim to replicate the real conditions of the building structures. However, most of the tests on beams found in literature do not include gravity loads in the cyclic loading history. An experimental campaign was carried out. Two beam specimens, named CB0 and CB1, designed to exhibit different failure modes were subjected to a loading protocol that involved the imposition of reversed cyclic loading and simultaneous gravity load. The aim was to validate the test procedure for different beam failure modes. Consequently, specimen CB1 failed by rupture of the tensile reinforcing bars while specimen CB0 failed due to concrete crushing and buckling of the compressed reinforcing bars. Results show that the presented loading protocol does not control the failure mode of the specimens. The specimens were also simulated numerically, and the results were comparable with the experimental observations in terms of load capacities, crack patterns, and failure modes.
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