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15. Effect of fibre characteristics on physical, mechanical and microstructural properties of geopolymer concrete: A comparative experimental investigation.

Author

Kantarci, Fatih

Subjects
*POLYMER-impregnated concrete, *INORGANIC polymers, *ULTRASONIC testing, *POLYPROPYLENE fibers, *GLASS fibers, *FIBERS, *SCANNING electron microscopes, *COMPRESSIVE strength
Abstract

The main aim of this work is to comparatively reveal the effect of fibre type, length and content on compressive strength and microstructure of structural geopolymer concrete (GPC) produced under constant mixture and curing parameters in order to address the significant gap in present literature. Firstly, GPCs with different NaOH concentrations (i.e., 6, 9, 12 and 15 M) and activator solution/binder (a/b) ratios (i.e., 0.45 and 0.55) were produced in ambient curing condition, and optimum production parameters were determined based on the preliminary evaluations. Then, glass and polypropylene fibres in 6‐mm length (GS6 and PP6) and polyamide and polypropylene fibres in 12‐mm length (PY12 and PP12) were included in GPCs at ratio of 0.4%, 0.8% and 1.2% (by volume). Compressive strength, apparent porosity, bulk density, ultrasonic pulse velocity (UPV), X‐ray diffraction (XRD) and scanning electron microscope (SEM) analysis of GPC samples were carried out comparatively. The inclusion of GS6 fibre enhanced the compressive strength thanks to fibre surface being covered by geopolymer gel and the strong adhesion between GS fibre and geopolymer matrix. SEM images of fibre reinforced GPC (FRGPC) also confirmed the experimental findings, which were attributed to improvement in compressive strength. Regardless of the fibre type, the maximum compressive value strength was obtained from GPC specimens with 0.4% fibre and then decreased. Higher fibre inclusions led to poor compaction, workability issues and inhomogeneous fibre dispersions. A very good relation (R2 = 0.98) was acquired between UPV and compressive strength values of GPC/FRGPC samples. [ABSTRACT FROM AUTHOR]

Published
2023
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19. Structural behavior of RC beams strengthened using fiber‐reinforced polymer U‐jackets.

Author

Maras, Muslum Murat and Kantarci, Fatih

Subjects
*CONCRETE beams, *FAILURE mode & effects analysis, *SUSTAINABLE buildings, *CARBON fiber-reinforced plastics
Abstract

The study aims to identify flexural behavior of RC beams strengthened using three different fiber‐reinforced polymers (FRPs) with differential cross‐sections configuration (i.e., middle and support sections). The experimental and calculations results of strengthening methods for RC beams were investigated utilizing FRPs under flexural loading. The strengthening FRP materials (CFRP, AFRP, and GFRP) were externally attached to the surface of the samples with U‐wrapped shape at the three different regions of the beams. The experimental results were compared with the fiber polymer systems of the American Concrete Institute according to the ACI 440.2R‐08 standards. The results demonstrated that RC‐9 specimen reinforced using AFRP exhibited higher load capacity performance than the others. The RC beams strengthened at both middle and support area exhibited more ductile behavior, which depends on the failure mode. Less crack formation was seen in the RC‐10 beams reinforced with AFRP, both in the middle and in the support area, compared with reference sample. The experiment revealed that FRP U‐jackets could be a promotive alternative to improve structural performance greatly and provide reliable and suitable solutions for sustainable buildings. [ABSTRACT FROM AUTHOR]

Published
2023
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23. Evaluation of Gastrocnemius Spasticity With Shear-Wave Elastography in Children with Cerebral Palsy after Botulinum Toxin Injection: Defining A Proper Position for Measurement.

Author

Gorgun, Baris, Dikici, Atilla Suleyman, Botanlioglu, Huseyin, Kantarci, Fatih, and Inan, Muharrem

Subjects
SPASTICITY, BOTULINUM toxin, ELASTOGRAPHY, CEREBRAL palsy, JOINT stiffness, TREATMENT effectiveness
Abstract

Aim: Cerebral Palsy (CP) is the most common neuromuscular disorder in children and it is characterized by a dysfunction in movement and posture. Botulinum toxin injection is a treatment method used for muscle spasticity in patients with CP. Elastography is a new method which is used for measuring muscle stiffness. This study aims to evaluate the gastrocnemius muscle stiffness in cerebral palsy patients before and after botulinum toxin injection by using the elastography method and contribute to the establishment of a treatment algorithm with a proper position for measurement. Materials and Method: The participants of this study were chosen from the patients of our hospital's orthopaedics and traumatology department. Among the patients on whom botulinum injection to gastrocnemius muscle was planned, 30 patients were randomly selected. Elastography of both gastrocnemius muscles were taken before the injection of botulinum toxin, in the third week and third month after the injection. Simultaneously with the elastography, Modified Ashworth Scale (MAS) values were noted. In hemiparetic patients, contralateral legs were taken as the control group. Results: The elastographic values of the medial head of gastrocnemius when the knee is in extension and ankle in passive dorsiflexion, were found to be statistically significantly related (p<0.05) to the MAS values before botulinum toxin injection, third week and third month post-injection. Conclusion: Stiffness due to spasticity in gastrocnemius muscle in CP patients was demonstrated through elastographic evaluation. A correlation was found between clinical MAS values. The most proper position was in which the knee is fully extended and the ankle is passively dorsiflexed. Elastographic measurements may be able to be used in these patients as a method of diagnosis in the future and it will help to assess the effectiveness of the treatment after the injection of botulinum toxin. [ABSTRACT FROM AUTHOR]

Published
2023
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