Current Materials Science - Volume 14, Issue 2, 2021

Background: There is a requirement for internal curing, especially in areas where water is scarce and where it is difficult to cure concrete due to inaccessibility of the site. About five times higher water is consumed in curing than the water used in making concrete. Furthermore, the quality of water that is to be used for these activities is required to be of a certain standard. If the requirement of water can be reduced, it becomes both economically and ecologically viable. Objective: The present research is carried out to determine the technical and economic feasibility of bentonite as an internal curing agent with properties of concrete to be used in the field. Methods: This paper compares the compressive and flexural strength parameters for standard and bentonite infused concrete and whether this can be considered as a suitable addition in concrete. The flexural strength is measured using four-point test. Both the tests are carried out in accordance with IS codes. Results: There is an increase in compressive strength for both intermittent and air curing of internally cured concrete in comparison to control concrete. Furthermore, air curing of internally cured concrete is comparable to intermittent curing of control concrete. Also, the compressive strength of intermittent curing concrete with bentonite is comparable with the strength obtained by pond curing of control concrete. Conclusion: The results indicate that bentonite can be considered as a viable addition to concrete, especially in cases of air curing. The use of bentonite is thus recommended for air curing and intermittent curing conditions.

Background: The previous studies have focused curing effect of mainly on high strength concrete, where strict supervision is maintained. This study is based upon general purpose concreting work for commercial and residential construction in absence of skilled manpower and supervision. Objective: The objective of this study is to establish a thumb rule to provide 7 days initial curing for maintaining quality for unsupervised concreting irrelevant to type of cement and grading. Methods: In this study concrete samples made with locally available commercial cements were cured for various initial exposure. Results: The results shows that concrete cured after a gap of 4 days from the time of de-moulding have given lowest strength as compared to concrete cured in standard practices i.e. where proper curing protocol had been followed. Conclusion: Initial curing is most important aspect of gaining desired strength. The findings after this study shows that curing affects the strength of concrete in variable grading. Initial curing has great importance for concrete with all types of Portland cement. Concrete with supplementary cementitious materials gives lowest strength initially but results higher strength after 28 days as compared to Portland cement.

Background: OLED material is always having much science to explore in them. The role of rare earth Dy as a dopant material in well studied In2O3 is studied. Objective: The candidature of the white light emission from the Organic light emitting diode is explored in the present work. Methods: The doping concentration effect and the corresponding emission is shown in the present work. It is emphasized that the doping at nearly x = 1 mol% of dysprosium could alter the transition states and the output of the emission is pure white which is corresponds to the luminescence peaks. Color purity and co-related color temperature was calculated by CIE technique. Results: The spectroscopic parameters are calculated by Judd-Oflet approaches which is suitable for RE³⁺ (RE= rare earth) ions. Conclusion: The present prepared phosphor is suitable for white light emission and used in display devices applications.

Background: Ductile irons provide a more viable alternative for malleable cast iron in areas that do not demand extreme wear resistance. Austempering of ductile irons was a well researched area in the last two decades. Attempts to further improve the wear resistance led to the development of Carbidic austempered ductile iron (CADI), wherein the carbides contribute to wear resistance. Combination of ausferritic matrix, graphite nodules, and carbides (eutectic and alloy) symbolizes the microstructure of CADI. Methods: Two principal approaches adopted by the researchers to change the microstructure are (i) addition of carbide forming elements (ii) heat treatment (s). Results: Both the above methods result in the refinement of graphite nodules, carbide precipitations, along fine ausferrite. Conclusion: Improvement in hardness, toughness and wear resistance was observed largely as a consequence of fine carbide precipitations and formation of martensite.

Background: The Scanning Vibrating Electrode Technique is an important method in the field of corrosion. The technique has helped researchers to understand corrosion mechanisms in real time, due to the availability of commercial systems, which are user-friendly, having a high degree of sensitivity and reliability. The technique provides quantitative and qualitative measurements by utilising a vibrating probe at a fixed height over the sample. Objective: The paper provides a basic understanding of the technique, including a brief history, development, method of measurement and then highlighting some applications of the technique. Conclusion: The paper shows the usefulness of the technique and its’ importance in corrosion research.

Background: A large amount of phosphogypsum occupies the land and causes environmental pollution. It is of great research significance and urgency to the utilization of the phosphogypsum. Methods: The influence of the ratio of the cementing materials and phosphogypsum (C/P ratio) on the compressive strength, water absorption, softening coefficient and freeze-thaw stability of the phosphogypsum baking-free bricks was investigated. The consolidation process of the phosphogypsum baking-free bricks was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results: XRD patterns show that the phosphogypsum baking-free bricks curved for 28 d are mainly composed of monoclinic CaSO4·2H2Oand hexagonal Ca6Al2(SO4)3(OH)12·26H2O (Aft) phases. SEM observation shows that the phosphogypsum bricks consist of Aft nanorods and irregular microscale particles. The softening coefficient, water-resistant performance and freezethaw stability of the phosphogypsum baking-free bricks remarkably decrease with decreasing the C/P ratio. 28 d compressive strength decreases from 26.42 MPa to 15.58 MPa with the change of the C/P ratio from 1:1 to 1:2.5. The optimal ratio of the cementing materials and phosphogymsum is 1:1. The phosphogypsum baking-free bricks exhibit good stability after 18 freeze-thaw cycles. Conclusion: Phosphogypsum baking-free bricks were prepared by natural curing process using phosphogypsum as the raw materials, cement, slag, fly ash and silica fume as the cementing materials. The phosphogypsum baking-free bricks exhibit great application in the field of building materials.

Background: Nanoparticles are structures up to 100 nm in size. Estimation of their size is usually determined by assessing of images obtained from scanning electron microscopy (SEM) and/or transmission electron microscopy (TEM) techniques. Studies on the effect of visual cognition on the analysis of these types of images are limited. Objective: The aim of the research was to determine whether students’ visual cognition influences the identification, analysis, and measurement of nanoparticle size through SEM and TEM imaging using ImageJ software. Methods: The visual cognition of each participant was evaluated by recognizing individual nanoparticles and measuring their diameter using ImageJ software. Finally, the Kruskal Wallis test was performed for statistical analysis. Results: Participants applied or not four main identification criteria in order to identify individual nanoparticles: shape, high contrast, defined edges, and presence/absence of agglomerates, being “shape” the predominant parameter taken into account to measure the diameter using ImageJ. Average diameters, number of measured nanoparticles, and standard errors of measurements varied between groups in all analyzed images, evidencing the influence of visual cognition on the measurements. Conclusion: We conclude that there is an effect of visual cognition in the identification of nanoparticles and their diameter estimation. The user’s training, background, experience, perspective, and operational conditions of SEM/TEM play a fundamental role in estimating the size of nanoparticles measured in microphotographs using ImageJ.

Background: The objective of sustainable development in the field of materials necessitates and demands the substitution of the basic constituents of a composite material (carbon, glass, etc.) by natural reinforcements, which have a very important role in the protection of the environment and to subsequently have new materials with good properties compared to socalled traditional materials. Objective: In this context, we have investigated using genetic modeling based on probabilistic models the effect of thermal stress on transversal damage of a bio-composite hybrid Flax- Hemp/PE material. Methods: Our model genetic is based on probabilistic models of Weibull and the different values of the thermal stress were calculated by the Lebrun equation. To validate our theoretical calculations, we used the nonlinear parameter β in the Hoock law of the nonlinear acoustic technique to trace the curves of the damage under the mechanical and thermal stress. Results: The results obtained with a genetic simulation are in good agreement with the results found by Clément Gourier and Raphaël Kueny, who have shown that flax and hemp fibers (bark/Liberian fibers) are good reinforcements of the Polyethylene matrix; we found also found that our hybrid biocomposite material Flax-Hemp/PE is resistant in particular, a part of this material is of plant origin and gives us environmental benefit. Conclusion: It should be noted that the results obtained by the genetic simulation are in good agreement with the results obtained by the nonlinear acoustic technique mentioned by the green curve in all the figures. In perspective, it would be interesting to see, later, the effect of humidity on the damage of the matrix fiber interface of a hybrid biocomposite.

Background: The serviceability of a sewn garment is influenced by the quality of its seams, which form the basic structural element. The factors that affect seam quality in garments include, sewing thread type and stitch density. Their right choice helps with the achievement of quality seams in garments. However, the choice of suitable sewing threads and stitch densities for particular fabrics can only be determined through testing. Objective: Problems associated with the poor performance of school uniforms include seam failure. The aim of the study was to determine sewing thread brand and stitch density suitable for seams for a selected fabric (79% polyester and 21% cotton) for Ghanaian public basic school uniforms. Methods: A 2×3 factorial design was employed, which involved two brands of sewing threads labelled A` and B` and three ranges of stitch density, 10, 12, and 14. The total number of specimens prepared from the selected fabric was 81. The parameters investigated included fabric weight, strength, and elongation, seam strength, seam elongation, and efficiency. The data were analysed using the Predictive Analytics Software (SPSS). Means and standard deviations of the fabric’s yarn count, weight, strength, elongation and the linear density of the sewing threads were determined. Analysis of Variance and Independent samples t-test at 0.05 alpha levels were employed in testing the hypotheses. Results: Differences in seam strength, efficiency, and elongation were significant for the two sewing thread brands and the three stitch densities in both warp and weft directions of the fabric sample. The sewing thread brand B′ with stitch density 14 performed best in terms of seam strength, elongation, and efficiency. Conclusion: The sewing thread brand B′ and stitch density 14 are recommended to be used for the construction of uniforms with the selected fabric to achieve quality in uniforms.