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The present paper aimed to experimentally investigate the effect of micro steel fibers (MSF) on the structural shear behaviour of SCC deep beams made of 100% RA. Flexural test were performed on six simply supported deep beams under a single-point loading scheme at shear span to effective depth ratio (a/d) of 1.2 and 1.5. Two SCC beams were made of natural aggregates (NA) without MSF, two beams were made of a 100% RA without MSF, and the last two beams were made of RA with MSF at a volume fraction (vf) of 1%. The parameters considered in this research included load deflection response, ultimate shear failure load, and cracking pattern. The obtained results indicated that using RA considerably reduced the shear capacity of reinforced SCC deep beams in comparison with control mix, and that reduction was more pronounced when a/d ratio was decreased. At a given shear load value, the deflection of RA-based beams was higher than that of NA-based beam, regardless of a/d ratio. This clearly reflected the inferiority of RA particles. However, a comparable or even superior shear strength can be reached when up to 1% MSF was added. Based on this experimental investigation, it was demonstrated that the crack patterns of SCC deep beams prepared with NA, RA, and even MSF, were generally identical. Nevertheless, the crack width for beams with a/d of 1.5 seemed to be more visible than that of a/d of 1.2. [ABSTRACT FROM AUTHOR]

Although many treatment techniques has been implemented to enhance the performance of recycled aggregate (RA), its characteristics is still lower than that of natural aggregate (NA), and therefore, further treatment is needed in this regard. An experimental investigation to improve the mechanical performance of RA self-compacting concrete (SCC) was presented in this study. To achieve this purpose, RA was first subjected to a simple treatment method by submerging it in a cement-silica fume slurry in order to enhance its physical performance. After completing the treatment process, several SCC mixes, incorporating NA, RA, and treated recycled aggregate (TRA), as well as micro steel fibers (MSF) with a volume fraction (Vf) of 0.5 and 1%, were prepared. The prepared mixes were tested in fresh state by slump flow, T500, and V-funnel tests, and in hardened state by compressive strength (fcu), splitting tensile strength (fst), water absorption, and unit weight. The results pointed out that the proposed treatment method is effective, such that the physical properties of TRA showed higher specific gravity and lower water absorption than that RA. With regard to the fresh properties, all the tested mixes, after the required superplasticiser dosage was added, met the self-compactibility criteria. For mixes without steel fibers, it was found that replacing NA by RA led to a considerable drop in fcu and fst values. However, a slight reduction in these values were noticed when TRA was used instead of NA. On the other hand, when TRA mixes comprised MSF, a significant improvement in fcu and fst were observed, particularly when 1% MSF was added. [ABSTRACT FROM AUTHOR]