Experimental Evaluation of Mechanical Properties and Fracture Behavior of Carbon Fiber Reinforced High Strength Concrete

Concrete without reinforcement is brittle which is intensified in high strength concrete. Fibers have been utilized to improve the tensile and bending performance of concrete. Fibers  primarily control the propagation of cracks and limit the crack width. Carbon fiber reinforced concretes are reliable structural materials with superior performance characteristics compared to conventional concrete. The addition of carbon fiber in concrete has been found to improve several properties, primarily cracking resistance, ductility and fatigue life. This paper reports a study on the mechanical and fracture properties of high strength concrete reinforced with different volume fractions of carbon fiber. Four different volume fractions between the range of 0.25% and 1.00% were chosen. Carbon fiber improved the compressive strength, load bearing capacity, fracture energy and toughness of concrete. Fiber volume fraction was more prominent factor in this regard. Fracture parameters showed better performance beyond 0.50% fiber inclusion

Effect of Prewetted Pumice Aggregate Addition on Concrete Properties under Different Curing Conditions

This study researches the effects of different curing conditions on the properties of high strength concrete containing presoaked pumice aggregate (PA). Fine normal weight aggregate is substituted by an equal volume of 1h and 24h presoaked PA at 50% and 100% fractions and a total of five concrete mixtures were prepared. After kept in water, air and hot weather, the performance of concretes were evaluated by determining their physical and mechanical properties at 28 days. Hot weather was found to be the most detrimental condition where the highest strength drops were observed. Frost resistance of concretes was improved with the use of presoaked PA at 50% replacement ratio. The use of presoaked PA also decreased the shrinkage values of concrete specimens. The results showed that the use of presoaked PA in high strength concrete at 50% replacement ratio could contribute to concrete properties when exposed to inadequate curing conditions

Experimental and Numerical Investigation of the Fracture Behavior of Particle Reinforced Alkali Activated Slag Mortars

This paper presents fracture response of alkali-activated slag (AAS) mortars with up to 30% (by volume) of slag being replaced by waste iron powder which contains a significant fraction of elongated particles. The elongated iron particles act as micro-reinforcement and improve the crack resistance of AAS mortars by increasing the area of fracture process zone (FPZ). Increased area of FPZ signifies increased energy-dissipation which is reflected in the form of significant increase in the crack growth resistance as determined from R-curves. Fracture response of notched AAS mortar beams under three-point bending is simulated using extended finite element method (XFEM) to develop a tool for direct determination of fracture characteristics such as crack extension and fracture toughness in particulate-reinforced AAS mortars. Fracture response simulated using the XFEM based framework correlates well with experimental observations. The comprehensive fracture studies reported here provide an economical and sustainable means towards improving the ductility of AAS systems which are generally more brittle than their conventional ordinary portland cement counterparts.Comment: This article has been accepted for publication in ASCE's Journal of Materials in Civil Engineerin

Microstructure and Strength Development of Sodium Carbonate–Activated Blast Furnace Slags

This paper presents the study of alkali-activated slags where sodium carbonate acts as a primary activator. The slow activation mechanism of sodium carbonate is accelerated by sodium hydroxide and with traces of calcium hydroxide. Strength development and the progress of hydration of the mixes were studied with the phase transformation and development of microstructural features through quantitative techniques such as thermogravimetric analysis and phase-identification techniques such as Fourier transform infrared spectroscopy and X-ray diffraction. Sodium carbonate replacement with sodium hydroxide and the presence of calcium hydroxide in the binder as a replacement for the slag enhances the rate of dissolution of slag, leading to faster strength development. Calcium hydroxide significantly increases the compressive strength, even at an early age. On the other hand, sodium hydroxide substitution is effective at later ages of the reaction when used at high dosages (e.g., 40%). Formation of strength-giving phases such as hydrotalcite and calcium aluminum silicate hydrate are confirmed with microstructure analysis and explain the strength development

Experimental and Numerical Investigation of the Fracture Behavior of Particle Reinforced Alkali Activated Slag Mortars

This paper presents fracture response of alkali-activated slag (AAS) mortars with up to 30% (by volume) of slag being replaced by waste iron powder which contains a significant fraction of elongated particles. The elongated iron particles act as micro-reinforcement and improve the crack resistance of AAS mortars by increasing the area of fracture process zone (FPZ). Increased area of FPZ signifies increased energy-dissipation which is reflected in the form of significant increase in the crack growth resistance as determined from R-curves. Fracture response of notched AAS mortar beams under three-point bending is simulated using extended finite element method (XFEM) to develop a tool for direct determination of fracture characteristics such as crack extension and fracture toughness in particulate-reinforced AAS mortars. Fracture response simulated using the XFEM based framework correlates well with experimental observations. The comprehensive fracture studies reported here provide an economical and sustainable means towards improving the ductility of AAS systems which are generally more brittle than their conventional ordinary portland cement counterparts

Assessment of Scapular Morphometry

WOS: 000454335600026The current study was undertaken to assess the incidence of different types of suprascapular notch, acromion dimensions and the lower and upper scapular angles. The suprascapular notch and variations of the acromion are clinically important in suprascapular nerve compression and subacromial impingement. Measurements were taken from 73 Anatolian dry scapulae of unknown age or sex. The suprascapuar notch was classified according to that of Rengachary et al. (1979). Its width and depth, the distance between supraglenoid tubercle and the deepest point of notch, as well as the upper and lower scapular angles were also determine measured. The type of acromion was assessed according to shape (type I (cobra), type II (square), type III (intermediate)) and tilt (type I (flat), type II (curve). Acromion length and the distance between acromion and coracoid process were also measured. The frequency of different types of suprascapular notch were type I (28.8 %), type II (23.3 %), type III (13.7 %), type IV (20.5 %), type V (2.7 %), type VI (5.5 %)and absence (5.5 %). Acromion type were type I (45.5 %), type II (7.5 %) and type III (47.0 %), acromion tilt type I (15.2 %), and type II (84.8 %). An understanding of the association between the anatomical structures of the scapula and morphometric measurements is clinically important

Anatomy and clinical importance of the extracranial clivus and surrounding structures

The aim of this study was to reveal the clinical importance of measurements taken from the pharyngeal tubercle (PT) to various anatomical structures around the extracranial clivus. Twenty-six adult dry Anatolian skulls were examined. The extracranial clivus and PT were used as landmarks from which various distances were measured using a digital caliper accurate to 0.01 mm. The following mean distances from the PT were observed; foramen lacerum (FL) (L: 17.15 mm, R: 17.4 mm); medial external margin of the carotid canal (CC) (L: 26.7 mm, R: 27.5 mm); anterior tip of occipital condyle (OC) (L: 16.4 mm, R: 16.3 mm); anterior margin of foramen magnum (FM) (10.8 mm); foramen ovale (FO) (L: 25.9 mm, R: 29.1); medial margin of the jugular fossa (JF) (L: 25.4 mm, R: 25.7 mm); medial external margin of the hypoglossal canal (HC) (L: 20.0 mm, R: 19.9 mm). Mean bilateral distances were: LFO-RFO: 45.34 mm; LFL-RFL: 20.1 mm; LCC-RCC: 52.1 mm; LOC-ROC: 17.6 mm; LJF-RJF: 45.2 mm; LHC-RHC: 33.5 mm. The following mean distances were observed from the FM: FM-OC (L: 8.3 mm, R: 9.3 mm); FM-HC (L: 17.8 mm, R: 17.4 mm). Also the mean distance of OC-HC were observed (L: 11.7 mm, R: 11.4 mm). Present measurements suggest that the PT can be used as an anatomical landmark during surgery involving clival pathology. However, the anatomy and variations of the extracranial clivus and surrounding structures must be taken into consideration.</p

The Variations of the Subclavian Artery and Its Branches

PubMedID: 10693329This study reports important variations in branches of the subclavian artery in a singular cadaver. The origin of the left vertebral artery was from the aortic arch. On the right side, no thyrocervical trunk was found. The two branches which normally originate from the thyrocervical trunk had a different origin. The transverse cervical artery arose directly from the subclavian artery and suprascapular artery originated from the internal thoracic artery. This variation provides a short route for posterior scapular anastomoses. An awareness of this rare variation is important because this area is used for diagnostic and surgical procedures