Mechanical Properties of Tibetan Rubble Stone Masonry Under Uniaxial Compression

Basic mechanical properties of Tibetan rubble stone masonry, a unique architectural structure in western China, may affect the bearing capacity of architectural structures. In this study, a compression test was carried out on a Tibetan rubble prism to investigate its failure mechanism and stress-strain characteristics under uniaxial compression. Based on the experimental results, we obtained two simple compression constitutive models for Tibetan rubble stone masonry, established equations applicable to predicting the compressive strength of Tibetan rubble stone masonry, and obtained a relationship between compressive strength and the elasticity modulus through a regression analysis.

The Potential Use of Brick Wastes in the Generation of New Materials for Construction through Geopolymerization Processes

The calcined clay bricks are the second most used materials in construction that, after the demolition processes, tends to become rubble, generating a negative visual and environmental impact, in addition to the fact that the brick-making process has not been industrialized in Ecuador, for that, its properties are deficient; in this way, the present research aims to study the physical, chemical and mineralogical characteristics of brick waste from the Southern part of ​​this country, for the elaboration of ecological bricks through geopolymerization processes, using as alkaline activator Sodium Hydroxide at temperature ranged between 90 °C and 200 °C, obtaining an optimal mixture at the combination 12.5 M, 26 wt% Cs, 150 °C. The mechanical properties of bricks as simple compression and flexural strength, respectively, applying the experimental Griffith criterion method by finite element simulation method. These ecological bricks obtained are suitable for use in construction.

Poly-ε-Caprolactone/Halloysite Nanotube Composites for Resorbable Scaffolds: Effect of Processing Technology on Homogeneity and Electrospinning

Polycaprolactone (PCL)/halloysite composites were prepared to compare the effect of homogenization technology on the structure and properties of the composites. Halloysite content changed from 0 to 10 vol% in six steps and homogeneity was characterized by various direct and indirect methods. The results showed that the extent of aggregation depends on technology and on halloysite content; the size and number of aggregates increase with increasing halloysite content. Melt mixing results in more homogeneous composites than the simple compression of the component powders or homogenization in solution and film casting. Homogeneity and the extent of aggregation determines all properties, including functionality. The mechanical properties of the polymer deteriorate with increasing aggregation; even stiffness depends on homogeneity. Strength and deformability decreases drastically as the number and size of aggregates increase. Not only dispersed structure, but also the physical state and crystalline structure of the polymer influence homogeneity and properties. The presence of the filler affects the preparation of electrospun fiber scaffolds as well. A part of the filler is excluded from the fibers while another part forms aggregates that complicates fiber spinning and deteriorates properties. The results indicate that spinning is easier and the quality of the fibers is better if a material homogenized previously by melt mixing is used for the production of the fibers.

Composite Materials Behaviour. Study, Development and Implementation of the Hypoelastic Model

The purpose of this research is to study and develop the formulation of a rheological law for composite materials with elasto-plastic behaviour in cold compression. Starting from the generally known relationships in literature, the hypoelastic model proposed for the composite materials behaviour (as powder materials) has been developped/explained, ensuring the understanding of the research. The hypolastic theory has been used for modeling the continuous transition from elastic to plastic state for a powder material. The material behaviour is described through an isotropic tensor relationship between the deformation speed tensor, Cauchy�s stress tensor and its derivative in relation to time (the Jaumann�s derivative). Only the linear part has been used from the general form of the law which depends on scalar functions. The calculations lead to relationships depending on five parameters which are identified according to experimental data. A numerical simulation of the stress-strain evolution during the simple compression of a diepressed powder sample is made; the numerical simulation has been validated by the experimental results.

Making the ecological brick using powder residues of Ceramic Tiles

The residues generated by the ceramic factories, among the most varied types, represent a large part of the waste produced and the one that comes from the production of red ceramics such as tiles and bricks, reflects in great part of all the constituents of these residues. The use of tailings is becoming an increasingly common practice, often because it does not have a correct final destination and in some places, there is a shortage of natural materials. The present work aims to study the addition of residues of ceramic tiles dust in the characteristics and properties of ecological brick. A literature review on the topic was carried out, in addition to granulometric characterizations, absorption tests, thermal comfort and simple compression. After carrying out the tests, the possibility of using it as a component of the ecological brick and using it in the region of Teresina-PI was studied. The samples produced with tile powder residue showed excellent results, therefore, through this study it was possible to prove that the reuse of these residues is valid for use in civil construction.

Study of the use of kaolin waste as a partial substitute for fine aggregate in the production of concrete for pavers

The study of the use of kaolin waste has scientific and socio-environmental value by providing an appropriate destination, reducing the demand and consequent problems arising from its extraction, considering that the construction industry is a consumer of a significant amount of raw material. Thus, the study aims to replace the fine aggregate by kaolin waste in the proportions of 10%, 20% and 30%, verifying its feasibility for interlocking sidewalk pieces. The kaolin waste was used with and without fine material, and physical characterization tests of the materials were performed, and then the concrete pieces were subjected to tests of resistance to simple compression, water absorption and resistance to abrasion, as prescribed by ABNT NBR 9781:2013, and flexural tensile strength test, according to ABNT NBR 12142:2010. According to the results and analyzing the compressive strength at 28 days, the mixtures with replacement of 10% of fine aggregate by kaolin waste reached strengths greater than 35 MPa, an acceptable normative parameter, both for the waste with fines and without fines, making its use feasible.

Innovative Materials for Sustainable Construction

The construction industry has focused on trying to minimize and control the environmental impacts caused within the process of production and manufacture of fired bricks, for this reason the present research proposes five different alternative mixtures for the elaboration of ecological bricks, four of these based on soil-cement and one obtained through a geopolymerization process, using raw materials from the amazon region and the southern highlands of Ecuador, such as soil from the Centza mine (MC), sand from the Quiringue mine (MQ), organic correctors of husk rice (RH ), peanut shell (PS), natural gypsum (G) from the Malacatos sector and fired brick residues from the same sector. The raw materials were characterized (analysis: physicochemical and mineralogical); the soil-cement-based combinations used different percentages of substitution of organic correctors and gypsum, the optimum percentage of water and cement was determined through the compaction test and resistance to simple compression respectively, the samples were cured and tested at ages of 7, 14 and 28 days. In the geopolymerization process, an alkaline solution NaOH was used in different concentrations of molarity and solution contents, the specimens were cured at temperatures of 90 °C, 120 °C, 150 °C, 180 °C and 200 °C. The different combinations were subjected to indirect traction with the purpose to determine the optimal mixture and subsequent estimation of the compressive strength of bricks applying the Griffith criterion, the results were validated by the finite element method, obtaining strengths of 4 MPa in the combination soil-cement sand (SC_Ar1), in soil-cement rice husk (SC_RH2) and soil-cement peanut shell (SC_PS2) mixtures its resistance is 3 MPa, while in the soil-cement gypsum (SC_G4) mixture the resistance is 6.90 MPa and finally the resistance in geopolymeric mixture (GBW) is 13.75 MPa; In this way, the optimal combinations comply and increase the resistance to simple compression of bricks by 35% the SC_Ar1 mixture, 130% in the SC_G mixture with respect to the spanish standard and 129% the GBW mixture with respect to the ecuadorian standard.

Influence of Carbon Nanotubes on Traditional Material

Brick as a material is of vital importance in the construction industry, however, the burning processes for its preparation contribute to environmental pollution and the generation of greenhouse gases; for this reason, the present research has as aims to propose quality traditional materials for sustainable buildings through the design of soil-cement mixtures in making brick using raw materials from the amazon region of Ecuador: Centza mine (MC) and Quiringue mine (MQ) and improve the mechanical properties of the brick by incorporating carbon nanotubes, which have been dispersed in two aqueous media, sodium naphthalene sulfonate (NSS) and calcium chloride (CC) in percentages of 0.5%, 1% and 1.5%. The characterization of the raw material (analysis: physicochemical and mineralogical) was of great help. The optimum percentage of cement and water was determined through simple compression tests and soil compaction respectively. The different combinations were tested at indirect traction strength at ages 7, 14 and 28 days, determining an optimal mixture for each group of combinations, in this way the simple compressive strength of bricks has been estimated using the Griffith criterion and validation of results by finite element method applying the CivilFEM software, obtaining a resistance of 4 MPa in mixtures of SC-Ar1, 6.3 MPa in combinations of MWCNTs NSS-9 and 5.3 MPa in mixtures of CC-4 MWCNTs, increasing resistance by 57.5% and 32.5% with respect to soil-cement bricks and qualifying them as suitable for use in construction according to standars.

Facile Fabrication of Free-Standing and Flexible Anodes Composed of Entangled N-Doped Carbon Nanotubes for Application in Lithium Ion Batteries

In this work, innate free-standing and flexible anode composed of entangled N-doped carbon nanotubes (CNTs) is fabricated by a facile annealing method following a simple compression without needing any tedious processing operations. The well cross-linked CNTs of the resultant free-standing anode enable robust diffusion channels for lithium ions and high flexibility. Served as the anode in lithium-ion batteries (LIBs) without the utilization of binder and current collector, the fabricated free-standing electrode can deliver a reversible area capacity of 2.14[Formula: see text]mAh[Formula: see text]cm[Formula: see text] at 1[Formula: see text]mA[Formula: see text]cm[Formula: see text] with superior cycling stability and excellent rate capability. The obtained reversible area capacity for the fabricated free-standing electrode material is much higher than that of the commercial graphite anode ([Formula: see text][Formula: see text]mAh[Formula: see text]cm[Formula: see text] at 1[Formula: see text]mA[Formula: see text]cm[Formula: see text]). Furthermore, the assembled full flexible battery utilizing the fabricated free-standing electrode also exhibits attractive performance and can substantially supply power for an electronic watch at flat and 180∘ bending positions, indicating the promising application in flexible electronic devices.