Characterization of Enhanced ITZ in Engineered Polypropylene Fibers for Bond Improvement

2022

Materials

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Deterioration of concrete structures is one of the major issues faced by the construction industry. Repair and rehabilitation are necessary to extend the service life of such structures. This study aims to investigate the effect of repair material type, length of repaired region, and loading regime on the structural characteristics of the repaired reinforced concrete (RC) beams. To achieve this goal, a total of 30 repaired and non-repaired RC beams were prepared and tested under static and repeated loading conditions. Three types of sounding-based non-destructive test (NDT) methods are employed to determine the material deterioration and sub-surface delamination after repeated loading. Results showed that under static loading conditions, full-length repaired beams had better performance than 1/3-span repaired beams. Beams repaired with cementitious repair mortar containing modified binder and cementitious repair concrete in full length had a yield strength that was 14% and 9%, respectively, higher than that of beams repaired in 1/3 span. All RC beams with full-span repair outperformed the intact beams. After repeated loading, beams repaired with cementitious repair with modified binder over full length showed a 14% improvement in yield strength compared to control samples. It was found that repair materials that had a high compressive and flexural strength are beneficial. The resonant frequency drops correlate well with the yield strength results. The formulas proposed by Canadian Standards Association (CSA) 23.3 can effectively predict the moment resistance of both intact (control) and repaired RC beams. The ratio of experimental moment resistance values to its predictions ranges from 0.91 to 1.04.

Section: Methodsmentioning

confidence: 99%

Evaluating Flexural Performance of Repaired Reinforced Concrete Beams under Static and Repeated Loading Using Non-Destructive Methods

Wang

2022

Materials

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“…All this information can be found in Table 2. More information about the properties such as freeze-thaw and corrosion resistance performance of the repair materials can be found in Wang et al [42,48,49] and Bajaj et al [50].…”

Section: Methodsmentioning

confidence: 99%

Performance of Repaired Concrete under Cyclic Flexural Loading

Wang

2021

Materials

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There is limited research reported on the effect of cyclic loading on cement-based repair materials as conducting such tests is time consuming. To overcome this issue, this study utilized a novel loading regime consisting of cycle groups with increasing stress amplitude to accelerate the test process. The Palmgren-Minder rule was used to estimate the fatigue life of repaired specimens. Specimens repaired with Mix M (cementitious repair mortar), which was estimated to have the highest 2-million-cycle fatigue endurance limit (77.4%), showed the longest fatigue life (95,991 cycles) during the cyclic loading test, the highest slant, and splitting bond strength among all repair mixes. The estimated two-million cycle fatigue endurance limit of Mix S (70.8%) was very similar to that was reported in literature (71%) using the traditional loading method. This study confirms the usefulness of Palmgren-Minder rule on estimating the fatigue life of repaired specimens. Additionally, the use of the novel loading regime showed the benefit of shortening the test process while producing results similar to those from using traditional loading methods. To improve the prediction accuracy, future research is required to modify the failure criteria to accommodate specimens that may not fail even when the average flexural strength is met.

“…Using nano particles to coat fibers will also increases the final cost of fiber production [26]. As a result, fiber coating with low-cost environmentally friendly SCM can be considered to be a sustainable method to improve ITZ and to the best knowledge of authors, few studies with limited fiber and SCM type have been investigated so far [27]. In this study, two novel methods were proposed to coat PP and CF fibers in to improve the mechanical behavior and enhance the ITZ.…”

Section: Introductionmentioning

confidence: 99%

Influence of Polypropylene, Carbon and Hybrid Coated Fiber on the Interfacial Microstructure Development of Cementitious Composites

Monazami

2021

Fibers

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Concrete is the most used construction material in the world; however, its deficiency in shrinkage and low tensile resistance is undeniable. Used as secondary reinforcement, fibers can modify concrete properties in various ways. Carbon-fiber-reinforced concrete is highly suitable to maintain longevity of infrastructure where corrosion of steel can shorten the useful service life of the structure while polypropylene fibers can mostly improve the shrinkage of concrete. However, the biggest challenge with fiber-reinforced concrete is the appearance of the poorly structured interfacial transition zone around the fibers. In this study, environmentally friendly and low-cost attempts were made to coat fibers with fly ash to enhance the structure of mortar around the fibers. Coated carbon and polypropylene fibers were used in mortar in single and hybrid forms to investigate the efficiency of fiber coating methods on mechanical and durability properties of fiber-reinforced cement mortar. A minimal dosage of 0.25% and 0.5% (by volume) PAN-based carbon fiber and polypropylene fiber was added to mortar to make low-cost mixes. Compressive, tensile and three-point bending tests were done after 14 and 28 days of curing, and the results were analyzed. The results showed higher compressive strength in coated fiber-reinforced samples and comparable results in tensile strength, flexural strength, and toughness parameters. Scanning Electron Microscopy (SEM) photos and Energy-Dispersive X-ray (EDX) analysis approved the efficacy of the coating methods.