Abstract
A large volume of concrete debris is being produced in many countries on the globe due to the demolition of old concrete structures and testing of concrete specimens in laboratories. One of the ways to reuse concrete debris is to produce Recycled Aggregates (RA) and use them in new concrete. In recent years, Recycled Aggregates Concrete (RAC) has experienced increasing demand in various non-structural and structural applications. In reinforced concrete structures, one of the sources of brittle failure is sudden loss of bond between reinforcing bars and concrete in anchorage zones. Therefore, for the structural application of any new kind of concrete such as fiber reinforced RAC, knowledge of bond characteristics of reinforcing bars embedded in concrete becomes essential for determining the overall structural response under different modes of loading. In this regard, this study experimentally investigated the effect of fibers on the bond stress-slip behavior of deformed steel re-bar embedded in RAC. Concrete mixes having 0, 50 and 100% RAs were prepared with and without the addition of fibers. Two types of fibers were investigated in mono form: hooked-ends steel and polypropylene fibers. The dosage of steel and polypropylene fibers was kept 40 and 4.4 kg/m3, respectively. Axial compression and standard pull-out tests were performed. Test specimens for pull-out test were prepared using deformed steel re-bars of 19mm (#6) diameter. The results of strength tests confirmed that the compressive strength of concrete is decreased by replacing Natural Aggregates (NA) with RAs. For bond behavior of steel re-bar, the results of this study showed that replacement of 50% NA with RAs did not affect the bond response of steel bar, however, 100% replacement of NA with RAs showed detrimental effect on bond stress slip behavior. The results further showed that the addition of both types of fibers made it possible to recover the loss in compressive strength, bond strengths and bond toughness occurred because of replacing NA with RAs. In case of RA concrete mixes containing hooked-ends steel fibers, strength values were found even greater than the strength values of Natural Aggregates Concrete (NAC). From the results of this study, it was found that it is possible to design a structural concrete mix using 100% RAs and steel fibers at relatively low dosage of 40kg/m3.
Highlights
Concrete is one of the most used construction materials in the world
The test specimens were designated according to the replacement level of Natural Aggregates (NA) in concrete with Recycled Aggregates (RA) such as Natural Aggregates Concrete (NAC), RAC50 and RAC100 and with respect to fibers used like Steel Fiber (SF) and Polypropylene Fibers (PF)
The results showed that the compressive strength of concrete is decreased as NA are replaced with RA
Summary
Concrete is one of the most used construction materials in the world. The production of concrete constituents such as cement and coarse aggregates has negative impact on our environment as a result of increasing CO2 emission and depleting reserves of natural resources. Xiao et al [1] compiled a comprehensive database of research studies on RAC from year 1996-2011 and reported that RACs can satisfy the requirement of mechanical strength and can be used as construction material It is a well-established fact that the addition of short discrete fibers of various types in plain concrete has positive impact on its mechanical properties with the exception of compressive strength, fibers certainly play positive role in post peak region of compressive stress strain behavior of concrete. The main objective of this experimental study is to understand the bond-stress slip behavior of deformed steel re-bars embedded in Fiber-Reinforced Recycled Aggregate Concrete (FRRAC) For this purpose, standard pull-out tests were performed on concrete specimens prepared using RAC with and without steel and polypropylene fibers reinforcement in mono form. Along with pull-out tests, compressive strength tests were performed on each concrete composition
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