Publication: Influence of crumb rubber aggregate and hybrid fiber on toughness and impact load of concrete structures
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Date
2020-11-01
Authors
Al-Wesabi, Emad Ali Haidar
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Abstract
Concrete structures are usually subject to dynamic loading conditions due to
impact loads. Researchers have investigated the incorporation of recycled materials
from worn automobile tires such as crumb rubber (CR) aggregate in concrete to
resolve the issue of waste tires and save the environment by making it green and
sustainable. The CR incorporation has resulted in improving energy absorption and
impact energy. It has also resulted in increasing ductility and strain capacity.
Nevertheless, using CR in concrete has had a negative effect, thereby causing a large
drop in mechanical properties. By focusing on concrete that contains CR particles
with hybrid fiber, this study aims to address issues of sustainability and strength
decline simultaneously and achieve a further improvement in toughness and impact
resistance behaviour because previous studies are limited. This study investigated the
hybridization of micro steel (MS) and polypropylene (PP) with various contents. The
various contents of MS fibres (0%, 0.75%, 0.825%, 0.9%, and 1.0%) and PP fibres
(0%, 0.1%, 0.175%, 0.25%, and 1.0%) at a similar volume fraction of 1.0%
with/without CR. All the fiber-reinforced rubberized concrete (FRRuC) contained
20% CR (1–2 mm in size) by volume as a fine aggregate replacement. The effect of
the hybrid fibers and CR on the mechanical properties has been evaluated by static
experiments. The structural performance of the compressive and flexural toughness,
as well as the fracture toughness parameters (fracture energy, fracture toughness,
critical energy release rate, critical j-integral, and characteristic length), have been
investigated. Furthermore, the impact resistance behaviors of plain and rubberized
concrete beam and slab specimens with reinforced hybrid fiber were examined
through repeated flexural impact load tests. The experimental results showed that the
fiber-reinforced concrete with CR produced higher toughness and impact resistance
compared with specimens without CR. By contrast, the mechanical properties
decreased, whereas the voids and water absorption of concrete increased due to the
CR replacement. The specimen, which is reinforced with 0.1% PP + 0.9% MS hybrid
FRRuC, has shown a significant improvement in toughness and impact resistance
behavior with the highest of all the mixes in this study. Furthermore, the results
showed improved mechanical properties of the specimens with 0.1% PP+0.9% MS
hybrid fiber. Accordingly, a successful mix of CR and hybrid fiber was achieved for
performance under impact load. Based on the promising results, there is high
potential of utilizing CR incorporation of hybrid fiber to be used in concrete for
improving the impact resistance of reinforced concrete structures such as shelters and
other strategic structures.