Key Engineering Materials Vol. 841

Abstract: To be more sustainable in the road construction industry, the rock-based geopolymer concept should be applied with an aim to create a geopolymer-based road structural layer. The research program studied on the geopolymer for road construction was newly established at Chiang Mai University, Thailand. This study concentrated in a preliminarily evaluation of strength performance and compaction characteristics of crushed rock-based geopolymer (CR-GP) to partially or totally replace the usage of ordinary Portland cement (OPC) as a road stabilizing agent. The standard crushed rock (CR), complying with the standard of road base materials, was obtained from a real construction field. The experiment on CR gradation, compaction and compressive strength were carried out. The results showed that CR of a finer grading curve with higher surface areas tended to better react with alkaline activators, resulting in relatively high compressive strength. The mechanical modification with compaction is one of the simplest methods for strength improvement. It found that higher compactive efforts (the modified compaction), higher densification than that of the standard compaction, corresponding to the compaction theory of soil mechanics. CR-GP having an ideal (reconstituted) grading curve achieved higher compressive strength than that of the standard grading one of a well-graded pattern. Overall, it could be concluded CR-GP has intrinsic compaction characteristics of which at its optimum point of compaction, CR-GP could address the minimum requirement for road standard in terms of compressive strength, by which it could be used as an alternative material in replacing the consumption of OPC.

Abstract: Material property that can describe its behavior under repetitive impact is an important data for the design and failure analysis of any engineering part. Study of this behavior by measuring the size of apparent damaged area at the surface (crater depth) and tracking the damage intensity is extremely difficult for small area. An attempt to develop the understanding of different response behavior during repetitive impact of stainless steel was made in this work. This paper presented the relation of the response signal to the contact surface condition in the repetitive impact test by mean of spectrum analysis. Acceleration response of a specimen under impact load could be affected by contact condition since contact area and local thickness of the specimen could be changed. The testing machine was developed to provide the repetitive impact force to the specimen. Surface morphology and depth of the crater were captured by optical microscope and 2D-stylus profilometer. The appearance in the peak spectrum amplitude of a response signal was found to be a noticeable response behavior that can differentiate the damaged specimen from the healthy specimen. Results of the response spectrum gave a clear relation to the damage intensity of the specimen. The increase in the peak amplitude during the number of impact cycles was found in the damaged specimen while the non-damaged specimen conditions the peak amplitude of the response is constant throughout the test.

Abstract: The properties of composite materials do not depend only on the properties of raw materials but also other parameters such as volume fraction, geometry, dimension and material distribution etc. Carbon fiber reinforced polymer is one of the top choices of composite material because carbon fiber has light weigh with high tensile strength. For fiber-based composite such as carbon fiber composite, directions of carbon fiber with respect to loading direction could also affect to the strength of composite material under load. In this work, the properties of short carbon fiber-resin composite were investigated (fiber length of 0.2 mm.) with two different fiber orientations, i.e. 0 and 90 degrees to applied load. The 3D printing technique was employed in order to control carbon fiber direction and minimize material loss leading to material cost reduction. It was found that 3D printing technique could control direction of fiber in most case. However, at area with high curvature, the unexpected fiber direction was observed due to post hot process during which material flow was expected. It should also be noted that fiber path during 3D printing process may be very crucial as it could result in low strength local area due to low fiber density. This area could promote stress concentration leading to final fracture.

Abstract: Limestone is one of the most ancient construction materials that exist, however it has become obsolete over the last decades, being replaced by industrial materials like cement. It must be considered that not only the construction lime can be used in works, but the limestone industry can provide other products like high purity lies The research about the surface area of high purity lime has verified that it exists an improvement in the adhesion and workability features of the material in comparison with construction lime, besides to be a more economical solution than masonry cement. It is proposed in this document the use of high purity lime in construction works to achieve the benefits previously mentioned. Various samples with different percentages of high purity limes were tested in the laboratory, analysing the surface area changes between them, considering its use for construction purposes and its performance.

Abstract: Nowadays, one of the biggest problems is the environmental contamination, which is attributed to a great variety of factors, among which is the construction, because one of the main synthetic materials most used is concrete, artificial material consisting of portland cement, fine aggregates, coarse aggregates and water, in the production and processing of portland cement a large amount of carbon dioxide (CO₂) is generated, by 2018 approximately 8% of CO₂ emissions from the world is attributed to the cement industry. As a solution to this problem, substitutions and additions to portland cement are proposed, which will generate a reduction in consumption and processing by having a more durable and better quality material in terms of physical and mechanical characteristics. Additions of 2% are made with respect to the weight of the cement of organic additions, which do not affect the behavior of the mortar. Cubic specimens were developed for tests of pulse velocity, compressive stress and accelerated attack of sodium sulfate to determine the durability of the material, where favorable results were obtained with organic addition of corn starch.

Abstract: This research is focused on cement pastes with w/c ratio of 0.5. The cementing material is Portland cement type II. The main aim is to estimate the mechanical properties based on non-destructive tests such as ultrasonic pulse velocity, and electrical resistivity by a correlation with the destructive tests such as compressive strength, flexural strength, and tensile strength at ages of 3,7,14,21,28 and 45 days. The results suggest that there is a good correlation between evaluated properties.

Abstract: The following investigation was carried out with the objective of characterizing a concrete added with an emulsion based on reused polystyrene. The tests that were carried out for this characterization are: compression resistance, resistivity and ultrasonic pulse speed, in addition to the proper characterization of the stone material. A control mixture was also made and one in which a fluidiser is added in order to compare the results of these mixtures against the results of the concrete added with emulsion. The proportions of the emulsion are 1% and 4% because in the setting times [1], made in previous research results in that 1% is the beginning of setting and 4% the end of it. Values greater than 4% exceed the time allowed in the NMX-C-177-1997 ONNCCE standard.

Abstract: In this paper, fluorosilicone oligomer and its curing agent are used as the main film-forming materials, and fluorosilicone POSS is added to reduce the surface energy of the composites to prepare a coating with certain anti-sticking effect. The changes of molecular structure before and after the reaction were obtained by infrared spectroscopy. The contact angle and anti-sticking property of the coating surface were studied by changing the content of POSS containing fluorine. It was found that the contact angle of fluorine-containing POSS reached 98.7° when the content of fluorine-containing POSS was 3 Wt.%. With the increase of POSS content, the anti-sticking force of composites changed little, but with the increase of the contact time of tape, the anti-sticking force showed an increasing trend.

Abstract: The magnetic and mechanical properties of the magnets Fe-Nd-B system are more dependent on the size and shape of the grain structure. The authors explored the effect of the neodymium content and the addition of transition metals (Mo, Co, Al) and rare-earth metals (Dy, Tb) on the formation of the structure alloy gas atomization powder the Fe-Nd-B system. It has been shown that doping enhances the formation of grain blocks with a radial gradient in the direction of grain growth. The alloying of a gas atomization powder alloy of the Fe-Nd-B system with rare-earth metals increases the anisotropy of the grain shape.

Abstract: The commercial activated carbon (AC) with enhanced adsorption performance capacity was studied via green functionalization. The adsorption of methylene blue (MB) from aqueous solution by deionized‑water functionalized activated carbon (DFAC) was investigated in a laboratory‑scale batch mode. The interaction effects of different operating parameters; adsorbent dosage (1‑5 g/L), pH (2-12) and agitation speed (100‑200 rpm) were studied. The ANOVA results suggested the quadratic model and the analyzed model were well fitted. The higher correlation coefficient, R² value of 0.93 and low p-value (0.0002) indicating the fitness of the response surface quadratic model developed. The optimum conditions were found to be the adsorbent dosage of 4.7 g/L, pH of 12 and agitation speed of 150 rpm, in which 99.74% of MB removal was achieved. Additionally, the confirmatory experiment was conducted to evaluate the accuracy of the optimized conditions in which the range of deviation is was 4.07%.