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PREPARATION AND ACELLULAR IN-VITRO BIOACTIVITY OF SOLID STATE SINTERED 45S5 BIOACTIVE CERAMICS USING BIO-WASTES AS ALTERNATIVE RESOURCES FOR BIOMEDICAL APPLICATIONS

In this research, rice husk ash (RHA) and eggshell ash (EGA) were used as biogenic materials for total replacement of pure quartz (SiO2) and calcium oxide (CaO) respectively in the traditional 45S5 bioactive glass composition by powder metallurgy route. Body formulation with nominal composition 45% RHA (SiO2), 24.5 EGA (CaO), 24.5% Na2O and 6% P2O5 was composed. The batch material was properly mixed with addition of 2% PVA (Polyvinyl alcohol) as binder and compacted at 70 MPa to produce compact samples of 40 x 20 mm. The samples were then allowed to dry in an ambient temperature followed by sintering at 1000°C for 2 h, then allowed to cool to room temperature. Selected samples were immersed inside prepared simulated body fluid (SBF – pH 7.4) at 37 °C for 5, 9, and 18h respectively. Physical, microstructure and phase evaluation were conducted to examine the developed bio-ceramic. The results showed the bio-waste based 45S5 bioceramic has bulk density and porosity of 1.02 g/cm3 and 62% respectively while deposits of carbonate-hydroxyapatite were found to increase with immersion period showing good bioactivity and affirm that the developed bio-waste based bioceramics are bioactive and can find suitable application bone repair.

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INVESTIGATING THE POZZOLANICITY OF BAGASSE ASH

This study aims to investigate the pozzolanic reactivity of bagasse ash while partially replacing cement. Rapid, reliable, and relevant (R3) testing techniques were employed. This was done by measuring the heat of hydration and by determining the amount of bound water. The blending of cement made the paste require more water, to enhance the setting time, have more peaks in a narrower range position of °2θ and with Aluminum containing compounds, to have a lower average crystallite size (16.46ηm) and lower diffraction angle. The cumulative heat flow in the blended samples decreased to 275.18J/g at 170hours and the maximum rate of heat flow decreased to 69.41J/gh which was found delayed at 5 minutes and 13 seconds. The difference in heat of hydration between the reference and blended sample increases as time increases starting from 3J/g on the 1st day to 9J/g on the 3rd day. Blended samples were found to have lower bound water(gram) (2.58%) content on day 1 than the reference. Compressive strength at an early age (≤ 1 day) is lower in the bagasse ash (BA) blended mortar cubes and during later days compressive strength of BA blended mortar cubes were the highest and quartz blended mortar cubes were the lowest. Besides, the pozzolanic activity of bagasse ash (PABA) was found to be 346.08mg of Ca(OH)2 per gram of bagasse ash. Results were compared with the strength development and pozzolanic activity determination test. The presence of pozzolanic reactivity of the bagasse ash was confirmed, and results were found to be coherent and in agreement with each other.

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INNOVATIVE EXPERIMENTAL TESTING PROGRAM OF DIRECT SHEAR TEST IN SOIL MECHANICS

The research work aims at analyzing for the first time the data set obtained on cohesive soil samples following the publication of the Romanian Invention Patent RO 134239. The standard test method for the direct shear test provides the shear strength parameter – internal friction angle in consolidated drained condition - of either undisturbed or remolded soil samples forcing the shear plane at the midsection of the sample in the horizontal direction. The samples are provided in parallelepipedal shape (6 cm x 6 cm x 2 cm) and the displacement rate in horizontal direction is 0.1 mm/min. The new equipment patented in Romania changes the direction of shearing, from horizontal to vertical, and the soil samples are of cubic shape (6 cm x 6 cm x 6 cm). The experimental program involves testing both the parallelepipedal and cubic samples using the same motorized mechanism, with simultaneous readings from their respective micro-comparators. The UU test is performed without allowing consolidation and shearing at 1.0 mm/min. For the CD test, samples are consolidated under vertical loads for 24 hours before shearing at 0.1 mm/min. The shear stresses for cubic samples were higher than those for parallelepipedal samples, with residual stresses reflecting this trend. For cubic samples, both the peak and residual shear stresses trend lines indicated higher cohesion (c) and lower internal friction angle (𝜙) for UU tests and CD tests in contrast to parallelepipedal samples in both testing conditions. The innovative testing program allows for variability in shear strength parameters along the soil failure surface in both natural and compacted soil structures. This differentiation divides the soil condition into drained and undrained states at the initiation, emergence points, and the point of maximum depth along the failure surface. This approach is significant for accurately assessing soil shear resistance and potential failure mechanisms. The study's findings suggest a nuanced approach to parameter selection for slope stability analysis, ensuring accurate representation of both cohesion and internal friction in stability models.

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GFRP COMPOSITES: A MATERIAL TO STRENGTHEN REINFORCED CONCRETE BEAMS WITH WEB OPENINGS FOR SHEAR

Buildings that require mechanical and electrical services must have utility pipes and ducts. The services include air conditioning, power supply, telephone lines, network cables, sewerage lines, water supply and etc. A reinforced concrete (RC) deep beam with web openings experiences excessive cracking and deflection, as well as a decrease in beam stiffness. Enlargement of these openings near supports would reduce beams’ capacity for shear. Hence, analysis and design of such beams require careful consideration, particularly with regard to their performance. In addition, design compliance to relevant codes and standards, and selection of suitable material properties and construction techniques are needed. When such an enlargement is unavoidable, strengthening of beam for shear and flexure is necessary. In this study, the use of GFRP (Glass-Fiber Reinforced Polymer) composites for strengthening of RC beams with openings is experimentally investigated. As compared to the control beam, test results showed that using GFRP was found to be effective in increasing the shear strength of beams with openings by 40% to 60%. Test results of beams with web openings exhibited higher shear strength than the predicted values whereas for strengthened beams with GFRP, code predictions are found conservative.

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A VERSATILE ADDITIVE MANUFACTURING INSTRUMENT: PHOTOPOLYMERIZATION-BASED 3D PRINTING AND CURRENT TRENDS FOR DENTISTRY AND ORTHODONTICS APPLICATIONS

The additive manufacturing route is a notably promising alternative option to obtain complex shaped parts, precise prototypes, and direct-usage system components for lots of independent sectors like medicine, dentistry, automotive, aviation, and construction. Compared to the conventional strategies, this methodology provides cleaner, healthier, and faster manufacturing opportunities for engineers and manufacturers. In this paper, actual applications of photopolymerization-oriented 3D printing in the field of dentistry are evaluated in light of the literature efforts, sectoral feedback, and additional original interpretations. Concordantly, the process backgrounds and printing materials were analyzed meticulously together with the evaluations of the physical and mechanical features of the dental components. When real implementations like models, surgical guides, aligners, temporary teeth, and implants are considered, it is seen that there is still a lot of room to be enlightened on this topic for a healthier future. In this context, this article aims to draw a broad perspective on the new interdisciplinary efforts and to emphasize the great potential of layer-by-layer production in the field of dentistry.

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