Key Engineering Materials Vol. 862

Abstract: Restoration works for the cultural heritage in México have commonly used traditional materials, being the slake lime one of the main solutions employed. Nevertheless, other lime products have not been studied or applied in patrimonial works. The main objective of this research was to verify if high purity limes can be used as an alternative for restoration works, knowing that they have a higher powder surface area and consequently great efficiency. Compressive strength and ultrasonic pulse velocity tests, (UPV), were carried on specimens of slaked lime and high purity limes in pastes and mortars, to compare the values obtained and decide in which restoration works they could be employed. Results showed a better performance of the high purity lime in mortars and slightly better values of the slaked lime for pastes.

Abstract: In the restoration field and the cultural heritage, the treatment of colour is very important, being an important factor for the decisions and interventions in historic buildings. However, some of these have not the same recognition and protection by authorities, being really vulnerable, especially against natural phenomena like the earthquakes. After the 2017 Puebla Earthquake, the remainders of the earthen architecture of Jojutla de Juarez were collected to be analysed. Natural clays of the quarries near the town were compared by colorimetry tests with the traditional adobe samples which were collected in the locality. There also were conducted particle size analysis and the Unified Soil Classification System, USCS, to obtain the composition and properties of the soils and the adobe bricks, as well as the additives used, mainly straw as fibre reinforcements of the adobe masonry. One of the factors observed which contributed to change the colorimetric values of the clays was the use of stabilizers like lime, on the other hand, these stabilizers also helped to change the USCS classification of the soils and their cohesive properties.

Abstract: The study of durability is very important because buildings are expected to last; since durability is attributed to the materials used in construction, the study of such materials is required. Among them, stones play a fundamental role as part of the structures, as well as stone aggregates in the elaboration of asphalt blends and concrete blends. Bearing this facts in mind, quarry stones of volcanic and crushed materials were studied in the mexican state of Michoacán.In this work, the Id2, density, and absorption data were correlated to obtain a mathematical model that helps predict Id2 and verify the relationship between the variables. On the other hand, logistic regression was used to classify rock quarries according to their durability index.

Abstract: The creation of sustainable hydraulic concrete from the use of waste materials, such as PET bottles, whose performance is better than the conventional concrete, has been a great challenge worldwide within the construction industry. This article shows a study on the application of PET fibers resulting from the recycling of post-consumer bottles, which will help increase their physical and mechanical behavior. Two concrete mixtures were made: a control mixture (M-C), with the proportions of a conventional concrete and a second mixture, adding 0.8% of PET fibers with respect to the cement mass (PR-0.8). Tests of electrical resistivity, ultrasonic pulse velocity, compressive strength, tensile strength and flexural strength were performed at the ages of 7 and 28 days. The results showed a slight improvement in the mechanical behavior of the PR-0.8 mixture, in contrast to the M-C mixture, given that a non-sudden failure occurs; while that the tests of electrical resistivity and pulse velocity indicate that the concrete produced is of good quality and durable.

Abstract: The inclusion of additions to concrete blends helps to improve performance in certain conditions. The analysis of two concrete blends was performed, a blend with the addition of a natural organic polymer and a control blend to make predictive models and find a correlation. Tree tests were performed: Electrical resistivity (E_r) test, Tensile strength (F_t) and Carbonation resistance. One of the most popular non-destructive tests on concrete is , due to the simplicity of measuring readings on concrete elements. It is a non-destructive test that determines the interconnectivity that exists in the concrete cementitious matrix by determining the quality of the concrete. The blend with the addition showed improved performance in all the tests. Data science techniques were used to generate artificial data, the Machine Learning technique (ML) is based on Tree regression (T_r) with satisfactory accuracy to assess the reliability.

Abstract: The structure and properties of graphene oxide aerogels (GOA), prepared by a modified Hummer’s method followed by a freezing-drying process in addition to a pre-oxidized procedure, were studied through FTIR, Raman, SEM and XDR techniques. FTIR results indicated the existence of -C-O, -C-OH and -C=O function groups on the GOA surface. Therefore, the D band intensity of GOA sample exhibited remarkable increasing in the Raman spectra compared with of graphite; it may be due to change the order-structure of graphite to disorder-structure of GOA. The diffractive peak for the graphite at 2θ of 26.5° vanishes instead the one around 10.0° occurred in the XRD pattern for the GOA supported that the structure and d-spacing changed seriously from graphite to GOA. The SEM images revealed that the micro-structure of graphene layer of GOA was wrinkler and softer than that of graphite, however, the former involved fewer lamellar layer appearance with wrinkles on the edges of the graphene. All the characterized evaluation confirmed that the graphite powder has been transformed into a GOA structure through the modified Hummers’ method.

Abstract: In this study, atomic force microscopy (AFM) was employed to characterize the microstructure of chitosan-zinc oxide (ZnO) nanocomposite. Three dimensional image of AFM indicated that ZnO nanoparticles were in the ranging of 0.25-33.33 nm in height, 13-177 nm in diameter (confirmed by particle size analyzer), irregular and triangular cluster in morphologies. Furthermore, ZnO nanoparticles were well incorporated into chitosan solution indicated by UV-vis absorption peak of 359 and 341 nm for ZnO alone and nanocomposite respectively. AFM revealed the relatively continuous matrix without pores, smooth and contoured film were formed from chitosan alone as well as chitosan-ZnO composites. There were no remarkable different for surface roughness of both films indicating ZnO in nano-scale were blended well with chitosan matrix.

Abstract: The synthesis of aluminum nitride (AlN) powders is traditionally completed through a thermal nitridation process, in which the reacting aluminum powders are combined with nitrogen at high temperatures with a long reaction time (usually several hours). Moreover, the occurrence of agglomeration within the melting Al particles results in a poor dispersibility of AlN powders, with a low efficiency of nitridation. In this study, an atmosphere-pressure microwave plasma preceded the rapid gas-gas synthesis process. In the reactor, the gaseous aluminum chloride (AlCl₃) reactant was fed at different positions (R1, R2, R3) to react with nitrogen at various reaction temperatures (690~1150°C) to rapidly produce AlN nano powders (in several seconds). The process was operated at a total flow rate of 13 slm with NH₃ gas content of 0 or 0.77% and an applied power of 1200/1400 W. Results showed that the high purity and dispersibility of AlN powders were found at a AlCl₃ feeding position closer to the resonant cavity of the reactor (R3, 1150°C). The AlN particle size was in the range of 25-50 nm. The experiments indicated that the gas-gas reaction for rapidly synthesizing AlN nanopowders can be successfully carried out via an AlCl₃-N₂ plasma-chemical approach.

Abstract: In this study, the PW91PW91 method with LANL2DZ level was carried out to settle the dispute about the most stable structure of Au₃^+/0/-. Molecular orbital analyses and Walsh diagram were adopted to rationalize our computational result about the ground state geometry of Au₃^+/0/-. Our results show that the most stable geometry of Au₃ is bent structure (C_2v) with bond angle 146.0°. The less stable structure is equilateral triangle structure (D_3h) with relative energies of 1.74 eV. The D_3h structure possesses multiplicity 4 while the C_2v structure 2. In addition, the most stable geometry of Au₃⁺ and Au₃^- are equilateral triangle structure (D_3h) and linear structure (D_∞h), respectively. The preference of geometric change can be rationalized simply by using Walsh diagram. Besides, the linear structure of Au₃ is found to be transition states (TS) of inversion of B-Au₃. The inversion barrier is estimated to be 0.04 eV.

Abstract: In this paper, three different plasticizer molecular sizes namely; glycerol (C3), tributyrin (C15) and trilaurin (C32) was used as non-carcinogenic plasticizers in poly(vinyl chloride) (PVC). The experimental results indicated that all the plasticizers play an important role of PVC toughening. Among of these plasticizers, tributyrin was the most effective for PVC plasticization due to its suitable molecular size. With the presence of tributyrin, PVC was found to tougher and softer which reflected as the increased tensile elongation at break, impact strength and the decreased tensile strength. Morphological study by scanning electron microscope (SEM) exhibited the localized plastic deformations in PVC/plasticized with 15 phr tributyrin. Dynamic mechanical analysis (DMA) showed some shifts of the glass transition temperature (T_g) for all the plasticized PVC compositions. The maximum shift was found when PVC was blended with 15 phr tributyrin. Migration test showed that the plasticizers were easily migrated in ethanol. For the migration in water, it did only slightly.