•Experimental investigation was conducted to determine mechanical properties and shrinkage of UHPFRC.•Numerical model was developed for the simulation of UHPFRC.•The efficiency of UHPFRC layers and ...jackets for the strengthening of existing beams was assessed.•Superior performance was observed in terms of stiffness, yield and maximum strength, when three side UHPFRC jacket was used.
In this study the efficiency of the use of Ultra High Performance Fibre Reinforced Concrete (UHPFRC) for the strengthening of existing Reinforced Concrete (RC) beams has been investigated. Experimental work has been conducted to determine UHPFRC material properties. Dog-bone shaped specimens have been tested under direct tensile loading, and standard cubes have been tested in compression. These results have been used for the development of a numerical model using Finite Element Method. The reliability of the numerical model has been validated using further experimental results of UHPFRC layers tested under flexural loading. Further numerical study has been conducted on full-scale beams strengthened with UHPFRC layers and jackets, and these results were compared to respective results of beams strengthened with conventional RC layers and with combination of UHPFRC and steel reinforcing bars. Superior performance was observed for strengthened beams with UHPFRC three side jackets, and the efficiency of this technique was highlighted by comparisons with other strengthening techniques.
•Hair and wave polypropylene fiber reinforced concrete (FRC) are evaluated.•Properties of FRC are compared with that of plain control mix.•HFRC and WPFRC properties are improved up to 19.1% and ...21.5%, respectively.•Application of FRC in concrete road is considered.•Cost saving (per lane per km) up to 3% can be made along with better performance.
Human hair fibers are abundantly available as waste and wave polypropylene fibers are commercially available. These fibers are studied with limited scope from only material point of view. In this study, the mechanical properties of hair fiber reinforced concrete (HFRC) and wave polypropylene fiber reinforced concrete (WPFRC) are explored for its possible applications in concrete roads. The properties are experimentally evaluated as per ASTM standards and the effectiveness of fibers in concrete are checked by comparing with that of control mix. In addition, by using the relevant properties, concrete road design is also compared. It is found that the compressive, flexural and splitting-tensile strengths of HFRC are improved by 12.4%, 16.2% and 19.1%, respectively, and that of WPFRC are increased by 11.7%, 21.5% and 17.5%, respectively. With these improvements, the thickness of concrete road for a particular studied loading condition can be reduced by 12.5 mm. This can result in cost saving (per lane per km) of 3% and 1.7% by use of HFRC and WPFRC, respectively. The performance of concrete road is also expected to be better because of improved toughness of HFRC and WPFRC.
•Response of UHPFRC beams subjected to load and fire exposure is presented.•Effectiveness of PP fibers in minimizing spalling in UHPFRC beams is investigated.•Spalling, load level and fire scenario ...have significant influence on fire resistance.
This paper presents results from an experimental study on the behavior of ultra high performance fiber reinforced concrete (UHPFRC) beams subjected to combined effects of structural loading and fire exposure. Five large-scale UHPFRC beams, fabricated with different batch mix proportions, were tested to evaluate the structural behavior and spalling performance under ambient and fire conditions. The test variables included the presence of polypropylene fibers, load level and fire exposure scenario. The test results show that UHPFRC beams are highly susceptible to explosive spalling in the compression zone (on the sides) of the beam section leading to lower fire resistance, as compared to conventional normal or high strength concrete beams. When polypropylene fibers are present in UHPFRC, the extent of fire induced spalling decreases, resulting in higher fire resistance. Results from fire resistance experiments indicate that higher load level aid in release of pore pressure through tensile cracking and decrease the extent of spalling in UHPFRC beams. In addition, UHPFRC beams with polypropylene fibers exhibit better performance under design fire scenarios with distinct cooling phase than under fire scenarios without a decay phase.
This paper presents a method to measure and visualize strains and cracks in high-performance fiber-reinforced concrete using distributed fiber optic sensors based on optical frequency domain ...reflectometry. Two beams were prepared using high-performance concrete with two types of fibers and post-tensioned with carbon-fiber-reinforced polymer (CFRP) tendons. The beams were instrumented with distributed sensors which were installed using two methods compatible with realistic construction. The beams were tested under four-point bending until failure. The distributed sensors measured strain distributions over the length of the beams in real time. The strain distributions are analyzed to detect, locate, trace, quantify, and visualize cracks during the processes of their initiation and propagation. The crack widths measured from the distributed sensors as well as a crack microscope are in a good agreement. This study is expected to promote distributed sensing technology for monitoring and control of construction and operation automation in new and existing structures.
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•Cracks are detected, located, quantified, and visualized using distributed fiber optic sensors.•Distributed fiber optic sensors can detect microcracks before they can be visually observed.•Practical methods are developed to install distributed sensors in new and existing structures.•Distributed cracks occur in high-performance fiber-reinforced concrete and are monitored.
•Applying an HDC layer to the compression zone of over-reinforced concrete beams effectively changed the brittle failure mode.•The strengthening effectiveness of HDC is significantly better than ...normal concrete.•The ductility of over-reinforced concrete beams is considerably improved by the HDC layer.•Strengthening effectiveness is improved as the reinforcement ratio and the strengthening thickness increased.
This study investigates the effectiveness of highly ductile fiber-reinforced concrete (HDC), which is characterized by its high ultimate compressive strain ability, in improving the failure mode and deformational characteristics of over-reinforced concrete beams. The flexural behavior of over-reinforced concrete beams strengthened with HDC was experimentally investigated. The variables included the tensile longitudinal steel reinforcement ratio, thickness of the layer, strengthening materials, and strengthening methods. The crack pattern, failure mode, load–deflection responses, flexural capacity, ductility, and strain were investigated. The experimental results indicated that applying HDC to strengthen the compression zone of an over-reinforced concrete beam is a highly effective method to change its brittle failure and improve the ductility. HDC-strengthened beams showed an increase in flexural capacity and deformation compared to normal concrete-strengthened beams with equal strengthening thickness. A better deformation capacity can be achieved by using a larger thickness of the strengthening layer, ensuring the coordination between the strengthening layer and the existing beam. The effectiveness of HDC in strengthening over-reinforced concrete beams was improved as the tensile longitudinal steel reinforcement ratio increased. A simplified calculation method for the flexural capacity of HDC-strengthened beams was proposed, which is in good agreement with the experimental results. The compression zone relative depth for the balanced failure could be notably improved by applying a larger thickness to strengthen the compression zone of over-reinforced concrete beams than the critical thickness of the HDC layer, which can be calculated by the proposed approach.
This study evaluated steel fiber corrosion and tensile behaviors of plain and self-healed ultra-high-performance fiber-reinforced concrete (UHPFRC) exposed to 3.5% sodium chloride (NaCl) solution. ...The degree of steel fiber corrosion was quantitatively evaluated via energy dispersive X-ray spectroscopy (EDS) and atomic force microscopy (AFM) image analyses. Test results indicate that, even after a 20-week immersion in the NaCl solution, only few steel fibers located near the surface of the non-cracked UHPFRC samples were slightly corroded, and they insignificantly affected the tensile behavior. A slightly better tensile performance was achieved by self-healing process, and it was further improved after exposure to the NaCl solution for a longer duration due to the moderately corroded steel fibers through the partially self-healed cracks. The surface roughness of the pulled-out steel fibers from the composites increased due to the self-healing and corrosion processes, relevant to the enhanced tensile performance, and by increasing the immersion duration.
•Influence of steel fibre jacket on the flexural behaviour of recycled aggregate concrete beams;•Lack of suitable model to predict the bending performance of strengthened recycled concrete beams with ...concrete jacket;•Development of a new model to forecast the flexural resistance of jacketed RC beams with steel fibres concrete jacket.
In this study, the effect of steel fibres reinforced concrete (SFRC) jacketing on the flexural performance of coarse recycled aggregate reinforced concrete (CRARC) beams is studied. A total of 48 reinforced concrete beams, in two categories, were manufactured and tested. In the first category, 16 reinforced concrete (RC) beams were tested, then strengthened with a jacket and tested again. In another category, 16 specimens were strengthened with a jacket and then tested. All specimens were tested using a four-point flexural setup. Coarse recycled aggregate (CRA) was used at two mass replacement ratios, 0% and 100%, in both RC beams and concrete jackets (CJs). Steel fibres (SF) was also added at 0% and 2% (by volume) in both beams and CJs. In these tests, the flexural capacity, maximum displacement at mid-span and the ductility of specimens were measured. Moreover, a new modified model was proposed to predict the flexural behaviour of SF jacketed CRA and coarse natural aggregate (CNA) beams. The obtained outcomes indicate that the maximum flexural strength and displacement of 100% CRARC beams increased substantially by strengthening RC with 2% SF reinforced CJs.
•The shear behavior of BFRP-BFRC beams was investigated experimentally and analytically.•The ultimate loading capacity and ductility of beams were improved with the addition of BMF.•The shear ...capacities of the tested beams were enhanced as their reinforcement ratios increased.•The GFRP stirrups resulted in lower ultimate strengths of beams than steel stirrups.•A modified shear equation incorporating CAN/CSA-S806-12 provisions was proposed.
This study investigated the shear behavior of basalt fiber reinforced concrete (BFRC) beams reinforced with basalt (B) and glass (G) fiber-reinforced polymers (FRP) bars and stirrups, respectively. Fourteen beams were tested under four-point loading up to failure. The investigated parameters were the volume fractions (Vf) of basalt macro-fibers (BMF), the reinforcement ratio, the shear-span-to-depth ratio, and the stirrup spacing. An enhancement in shear capacities of the tested beams was observed with the increase of the Vf of the added BMF from 0 to 1.5%. The shear capacities of the tested beams were also improved as their reinforcement ratios increased. On the other hand, there was a significant reduction in the ultimate strengths and stiffnesses of beams with GFRP stirrups compared to their counterpart beams with steel stirrups. The experimental capacities of the tested beams and experimental results of 178 FRP-RC beams available in the literature were compared to those predicted by existing models and code equations. A good correlation between the predicted and experimental results was obtained using the equations of CAN/CSA-S806-12. A proposed modified shear equation incorporating CAN/CSA-S806-12 provisions and a model suggested by Al-Ta'an and Al-Feel predicted the shear design capacities of BFRP-BFRC reinforced concrete beams with reasonable accuracy.
•Drop-weight impact tests were performed on steel or GFRP bars RC slabs.•Effects of bar type, reinforcement ratio and arrangement were investigated.•Effects of concrete strength and slab thickness ...were also investigated.•Singly RC slab with higher tensile bars than doubly RC slab perform better.•The results obtained from experiment and numerical simulation are in good agreement.
Reinforced concrete slabs are common structural elements that could be exposed to impact loading. Although use of reinforced concrete slabs and utilization of Fiber Reinforced Polymer (FRP) as alternative to traditional steel reinforcement slabs are growing, but the influence of various parameters on their response under impact loads is not properly evaluated. This study investigated the effect of rebar’s material, amount and arrangement of reinforcements, concrete strength and slab thickness on dynamic behavior of reinforced concrete slabs using both laboratory experiments and numerical simulations. Performance of fifteen 1000 × 1000 mm concrete slabs, including two 75 mm thick plain slabs, five 75 mm thick steel reinforced concrete slabs, six 75 mm thick reinforced concrete slabs with Glass Fiber Reinforced Polymer (GFRP) bars and two 100 mm thick steel reinforced concrete slabs under drop weight impact loads was experimentally investigated. Failure mode, crack development, displacement-time, strain-time, and acceleration-time responses were studied and compared between various slabs. Finite element analyses and simulation of specimens were conducted using LS-DYNA explicit software. The results obtained from experiments and numerical models are in good agreement, and they indicate that increasing the reinforcement ratio or the slab thickness enhance the behavior of RC slabs under impact loads. By adjusting the amount and arrangement of GFRP, better performance in GFRP slabs than steel reinforced slabs can be achieved, which considering the corrosion resistance of this material, can make it an appropriate selection of reinforcement material.
Over the past few years, polyolefin fiber reinforced self-compacting concrete has shown high performance in both fresh and hardened state. Its fracture behavior for small deformations could be ...enhanced with a small amount of steel-hooked fibers, obtaining a hybrid fiber-reinforced concrete well suited for structural use. Four types of conventional fiber-reinforced concrete with steel and polyolefin fibers were produced on the basis of the same self-compacting concrete also manufactured as reference. These concrete mixtures were manufactured separately with the same fiber contents being subsequently used for two more hybrid mixtures. Fracture properties, in addition to fresh and mechanical properties, were assessed. The research showed both synergies (with the two types of fibers working together in the fracture processes) and an improvement of the orientation and distribution of the fibers on the fracture surface.
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