The increasing use of polymeric reinforcements in concrete structures requires either the development of a new design theory or the adaptation of current designs considering the engineering properties of this type of materials. In this work a method for calculating the deflections of reinforced concrete elements is proposed, which can be used in predicting the flexural behavior of longitudinally reinforced concrete with PET strips in amounts up to 1%. The model theory assumes that concrete has a tensile load capacity different to zero, characterized by a uniaxial tensile stress-strain diagram. A series of tests were conducted to corroborate the validity of the suggested method, showing that the theory also correctly predicts the creep deformation post-cracking. The deflection results of reinforced concrete with recycled PET strips are presented. The tests are carried out by a simple beam with center-point loading, using three different amounts of reinforcement and comparing the experimental results with the theoretical results of the proposed model.

In the present study a new sandwich laminate is designed and mechanically characterized. The laminate is elaborated with a core of particulate composite material consisting of recycled material from milk and juice cartons (multilayer laminate of Tetra Brik®), and HDPE containers from Urban Solid Waste (USW). The elaborated material consists of aluminum facings with a particulate core, consolidated with a thermoplastic adhesive of polypropylene- maleic anhydride. The main properties under tension are evaluated under testing standards. Results show good compatibility in the union of elements, with potential applications in building facades and false walls for the construction and furnishing industries.

The topic of Urban Solid Waste (USW) has become increasingly controversial in our times due to the high volumes being produced and not disposed properly; one effective way to reduce the generation of USW is finding new ways to recycling. This study proposes a means of recycling Tetra Brik® (TBr) cartons and high density polyethylene recycled containers (HDPEr), by generating an agglomerate with optimal mechanical properties in comparison with other TBr-based agglomerates. For the analysis of this material’s mechanical properties, two types of evaluation tests are carried out; flexure and screw pull-out test. Results show significant mechanical advantages over other TBr-based laminates by the integration of an HDPEr matrix to the system, thereby improving mechanical properties.

A study of the fluid flow in a mixing device proposed to dissolve alloying elements in iron baths is performed through a mathematical model in order to predict the best operating conditions for a proper melting/dissolution of solid alloying particles. The mathematical model consists in the mass and momentum conservation equations (continuity and Turbulent Navier-Stokes equations), and the standard two k-epsilon turbulence model. The model is numerically solved in transient regime with the Volume of Fluid algorithm (VOF) to calculate the vortex shape. VOF is built-in the CFD (Computational Fluid Dynamics) software ANSYS FLUENT 14. A flow of metal enters tangentially in the mixing chamber of the proposed mixing device (taken from an open patent) to generate a vortex. The shape and height of the vortex reached in this chamber depends on several design variables, but in this work only the presence or absence of a barrier in the device is analyzed. Results are obtained on the vortex sizes and shapes, liquid flow patterns, turbulent structure, residence times of the particles of alloying elements added to the melt and mixing times (Residence time distribution curves) of two devices: one with a barrier and the other without this barrier. It is found that the presence of the barrier in the device increases turbulence, destroys the vortex, decreases the residence time of the particles, and decreases the volume of fluid in the device. Most of the features of the barrier are detrimental for mixing and inhibits melting/dissolution of the alloying elements. Then, it is suggested a device without the presence of barrier for better performance.

Shape Memory Alloys (SMA) are characterized by the capacity to recover a permanent deformation after being heated above a critical temperature called Final Austenite Temperature (Af). The Ni-Ti SMA are the most commercially used, however recent studies showed that the Cu-Al-Mn SMA present significant shape recovery and mechanical properties, showing a strong potential for developing new applications. In this context, the main goal of this work is to manufacture a Cu-Al-Mn SMA through a plasma melting process followed by injection molding of liquid metal and then characterize the samples, using the following techniques: Optical Microscopy (OM), Differential Scanning Calorimetry (DSC), Electrical Resistance as a function of Temperature (ERT) tests, Dynamical Mechanical Analysis (DMA) and Microhardness (MH).

Shape Memory Alloys (SMA) metallic materials that change their mechanical and physical properties with temperature variation and mechanical loading, surprising engineers and researchers. In this way, one can develop thermomechanical actuators capable, for example, of generating force by blocking the shape recovery or change the natural frequency of a mechanical system by blocking resonance. The processing of these SMA are countless, each one with its specific limitation and particularity. This study aims to evaluate the influence of rapid solidification of a Ni-Ti SMA that is originally manufactured by Vacuum Induction Melting (VIM) and reprocessed by Plasma Melting (PM) followed by injection molding into different metal molds (steel, brass, aluminum and copper). The influence of such a processing is analyzed through Differential Scanning Calorimetry (DSC) and Electrical Resistance as a function of Temperature (ERT) to determine the effects on transformation temperatures. The results demonstrate that by using the copper mold one can provide greater uniformity of the material properties. Thus, there is the possibility of obtaining different kinds of SMA mini-actuators by PM injection in a copper mold and that includes different shapes and sizes that can be studied further.

Ballistic grade composite materials have shown several advantages in comparison with their individual constituents, such as increased ballistic limit and reduced posterior trauma. One configuration in particular that has demonstrated greater ballistic efficiency is the arrangement of independent laminates (IL). It presents an increase in energy absorption compared to its counterpart of consolidated laminates (CL). In this study, an analysis is carried out to determine the effect on the ballistic performance of IL and CL arrangements when they are subjected to biaxial prestress (BP). Results show how the ballistic advantage obtained in IL is nullified in comparison with CL, thus demonstrating the limitations of this arrangement for possible applications where the arrangement is subjected to normal impacts with BP.

The aim of the present study is to analyze interfacial adhesion and characterize the tensile properties of a FML elaborated from thin layers of an aluminum alloy and layers of maleic anhydride modified polypropylene (MAHPP) reinforced with an aramid woven fabric. For the analysis of interfacial adhesion, a microbond test is carried out on the MAHPP-aramid fiber system and a single lap joint test is performed on FML constituent materials, as well as the tensile characterization of the FML and its constituents is conducted accordingly. Microbond testing revealed an improvement in interfacial shear strength for the MAHPP-aramid fiber system in comparison with that of polypropylene-aramid fiber systems reported in the literature. The apparent shear strength between the FML constituent materials is comparable to that for bonding of aluminum with MAHPP. Tensile characterization of the FML and its constituents showed that the FML presented greater tensile strength than the aluminum alloy; and a more ductile behavior in comparison with its individual components due to the degree of adhesion between the constituents which allows the material to deform in unison.

A mathematical model is developed to describe deoxidation of water in a physical model of a batch aluminum degassing reactor equipped with the rotor-injector technique, assuming that deoxidation kinetics of water is similar to dehydrogenization of liquid aluminum. Degassing kinetics is described by using mass transport and mass balance principles by assuming that degassing kinetics can be characterized by a mass transfer coefficient, which depends on the process variables. The transport coefficient and the average bubble diameter are estimated with correlations reported in the literature for similar gas-injection systems. The water physical model helped to validate the mathematical model and to perform a process analysis by varying: 1) Gas flow rate (20 and 40 l/min); and 2) Impeller’s angular velocity (290 and 573 rpm). Results from the model agree well with measurements of deoxidation kinetics at low impeller rotating speeds. At high rotating speeds the model is still valid but less reliable because it does not take into account the formation of the vortex at the free surface. Nevertheless, the model provides predictions of the influence of every operating parameter and it can be used as a good approximation for real systems.

The phase composition and the microstructure of multilayer ceramics synthesized by directed laser treatment of ternary powder mixtures of Al2O3–TiO2–Y2O3 have been studied. It is established that at R = 2.34 (where R is TiO2/Y2O3 in mol %) the main phases observed are Y2Ti2O7, α-Al2O3 and a little amount of β-Al2TiO5. The content of the formed phases is determined by the composition of the initial mixtures. The texture of the surface and the microstructure of the formed ceramics depend on the α-Al2O3 and Y2Ti2O7 content. Increasing the content of alumina in the initial mixtures, the surface of the ceramics is saturated by α-Al2O3 crystallites. When a multi-layer synthesis is realized, the Y2Ti2O7 phase is concentrated at the boundary between the two adjacent layers (top and bottom). In the underlying layer, the growth of the corundum crystallites is prolonged due to the additional heating.

The paper deals with the problems of mechanical properties of structural steels used for load-carrying structures of civil engineering constructions. The attention is mainly paid to the values of yield strength from the viewpoint of the design concept of European Standards, i.e. Eurocode 3 for the design of steel structures, with respect to the structural reliability given by the failure probability. In the case of other materials, concrete or timber for example, characteristic and design values of strength given by the corresponding failure probability are used in the design procedures, where the partial safety factor of material is γM > 1.0. However, in the case of steel, the nominal values instead of characteristic values of steel yield strength are utilized in the structural design procedure, with the partial safety factor for material of γM = 1.0. These values have been derived based on the statistical and probabilistic evaluation of the data sets of actual material properties obtained from various recent steel producers. The paper presents the brief information on the results of the study oriented to the influence of the nominal or characteristic value of yield strength on the design resistance, which is shown on the examples of the member subjected to tension and bending moment, respectively. The influence mentioned is shown using the examples of structural steels used in constructions of the age of about 40 and 100 years.

The formation of the structure of geopolymer binders based on low-calcium fly ash is a multifactorial process that depends on the degree of solubility of aluminosilicate components in the solution of alkali activator. It is observed that the geopolymer binders based on fly ash with an identical chemical and mineral composition, the same grain size, and also activated by the same alkalis can result in a different strength.

This study is based on the assumption that there is dependence between the solubility of aluminosilicate components and the degree of polymerization of the silicates in glass phase. The degree of SiO2-polymerization is an integral parameter that is equal to the Si molar ratio (fSi) of the silicate component in the glass phase of fly ash. The degree of SiO2-polymerization can be estimated from the molar composition of glass phase, which is determined from the chemical composition and quantitative X-ray diffraction analysis including identification of the amorphous phase composition.

The SiO2 polymerization rates of investigated fly ash specimens are confirmed by the IR results, specifically, by comparison of absorption bands of silicate fragments with varying levels of connectivity (Q0-4) in the range of wave numbers of 650–1350 cm-1.

The comparative analysis of the correlation of 28-day strength of geopolymer binders based on fly ash from different sources and level of SiO2-polymerization demonstrated an inverse relationship with fSi molar ratio and compressive strength.

The improvement of concrete workability can provide a considerable reduction of production expenses and also leads to significant improvement of construction quality. This paper reports on the development of self-consolidating concrete (SCC) based on local materials, such as metakaolin (MK) and aggregate fines. The use of metakaolin in SCC is found to be very promising, due to its ability to increase the flowability and segregation resistance of concrete mixtures. Furthermore, due to pozzolanic properties, the application of MK provides an improvement of concrete microstructure, strength and durability. The proposed SCC design includes the optimization of aggregates and combined aggregate-binder powders to target 0.45- and 0.3- power particle size distributions, respectively.

Asphalt concrete is the most common material for highway and motorway construction. The quality of asphalt is determined, to a large extent, by properties of asphalt binder. Fillers, which are mineral powders from carbonate rocks and aggregates fines, such as limestone and dolomite, are often used in the composition of bitumen mastics affecting the performance of asphalt.

This article explores the feasibility of using the fines of aluminosilicate sedimentary rocks as fillers. These materials are composed of clay minerals, which change their properties upon the contact with water. Normally, the use of such fillers is restricted because of poor water resistance and swelling of asphalt concrete. In order to improve the performance of these fillers, the thermal modification at moderate temperatures of 500–600 °C has been proposed. Such treatment provides sufficient structural stability of obtained materials and results in the reduction of water absorption of asphalt, improved water resistance (up to 2.5 times) and also, in reduced swelling (up to 9 times).

It has been demonstrated that improvement in the filler performance can be achieved by a heat treatment. Such treatment induces changes in the mineral composition and converts the structure of clay minerals into the frame structure of zeolite, as confirmed by X-ray diffraction and infrared spectroscopy. Due to thermal treatment, there is a change in the acid-base properties of the surface of the filler, which is reflected in the profiles of the main adsorption centers. As a result, due to chemisorption, the modified aluminosilicate fillers are able to interact with bitumen. The application of new filler materials in asphalt concrete enables to enhance the performance.

The aim of this work is to process by equal channel angular pressing (ECAP) a low carbon – triple-alloyed steel containing 0.2% C, 0.5% Cr, 0.6% Ni, 0.2% Mo and 0.8 Mo. The process is performed at room temperature for up to four passes using route Bc with an equivalent strain of ∼0.6 after a single pass. Structure evolution before and after deformation is studied using scanning electron microscopy (SEM) and x-ray diffraction (XRD) and mechanical properties are assessed by microhardness and tensile testing. A significant improvement of the mechanical properties is found with increasing number of ECAP passes. Micro-hardness increases from 216 HV for the initial sample to 302 HV after four passes and tensile strength increases to 1200 MPa compared with 430 MPa prior to ECAP. X-ray diffraction and SEM analysis show changes in the original ferritic-perlitic structure through ferrite grain refinement and the deformation of perlite. This nickel-chromium-molybdenum alloy is used in manufacturing as gear material, and when it is hardened and formed through carburizing or boronizing it can be used to make hard-wearing machine parts. However, the ECAP process has not been used to harden this steel and to change its structure to obtain better mechanical performance.

In many tropical countries coconut (coir) fiber production is a major source of income for rural communities. The Caribbean has an abundance of coconuts but research into utilizing its by-products is limited. Environmentally friendly coir fibers are natural polymers generally discarded as waste material in this region. Research has shown that coir fiber from other parts of the world has successfully been recycled. This paper therefore investigates the mechanical properties of Caribbean coir fiber for potential applications in civil engineering.

Approximately four hundred fibers were randomly taken from a coir fiber stack and subjected to retting in both distilled and saline water media. The mechanical properties of both the retted and unretted coir fibers were evaluated at weekly increments for a period of 3 months. Tensile strength test, x-ray diffraction analysis and scanning electron micrographs were used to assess trends and relationships between fiber gauge lengths, diameter, tensile strength and Young’s modulus. Diameters ranged between 0.11 mm-0.46 mm, while fiber samples were no longer than 250 mm in length. The tensile strength and strain at break decreased as the gauge length increased for both unretted and retted fibers. The opposite occurred for the relationship between the gauge length and Young’s modulus. Additionally, the tensile strength and modulus decreased as the fiber diameter increased. Neither distilled nor saline water improved the coir fiber’s crystalline index. Scanning electron micrographs qualitatively assessed fiber surfaces and captured necking and microfibril degradation at the fractured ends.

The analysis revealed that the tensile strength, modulus, strain at break and crystallinity properties of the Caribbean coir fibers were comparable to commercially available coir fiber which are currently being used in many building applications.

In this work the thermal and kinetic analysis of the cooling and solidification of a near eutectic Al-Cu alloy is performed using inverse thermal and solidification kinetics analysis. The Fourier thermal analysis is applied to experimental cooling curves to obtain data on solid fraction evolution and latent heat of solidification. Inverse thermal analysis is applied to calculate the global heat transfer coefficients that allow correct simulation of the cooling of experimental probes. The free growth method is used to obtain the eutectic growth coefficients. All the obtained parameters are feed into a heat transfer-solidification kinetics model to validate the methodology and results generated from this work. It is found a relatively good agreement between experimental and predicted cooling curves which suggest that this methodology could be used to generate useful information needed to simulate eutectic solidification.

This article deals with the development of autoclaved composites (AC) with nanostructured additive (NSA) and reports on the beneficial effects of NSA in autoclaved lime-silica mixtures.

Based on the results of X-ray diffraction and electron microscopy investigation, the effects of hydrothermal conditions on the mechanisms of lime-silica interaction are revealed. It is demonstrated that the addition of NSA intensifies the formation of the C-S-H phase, reduces the quantities of amorphous phases and enables the formation of low-base calcium hydrosilicates (11Å-tobermorite and xonotlite).

The physical and mechanical properties of autoclaved composites with NSA are investigated and optimized. The reported research demonstrates the feasibility of NSA application to improve the performance of autoclaved materials.

This paper reports on the development of a new type of low cost artificial aggregates based on granulated reactive silica (AAGS) for application in lightweight concrete. The functional principle of AAGS is based on the formation of polysilicate solutions under heat treatment (up to 80 °C) and migration of these solutions into the porous space of concrete under the thermal gradients, resulting in strengthening of inter-porous space. Developed AAGSs are based on low cost local raw materials, which may contain different amounts of amorphous silica. The activity coefficient (AC) and amorphous silica content are used to evaluate the performance of raw materials by suggested accelerated method.

Silica components with different genesis are investigated and ranked according to their AC. It is found out that chemogenic and biogenic siliceous rocks with a low degree of diagenetic transformations, which are mostly represented by CT-opals (a low-temperature nanoscale modification of tridymite and crystobalite, such as diatomite, tripoli and opoka) are the most highly active raw materials for AAGS. All tested siliceous materials including natural and artificial components are divided into three groups: highly active (with AC of 51–100%), active (with AC of 21–50 %) and low-active (with AC of 5–20 %). Based on theoretical and experimental studies, the requirements for AAGS raw materials are developed.

The annealing behavior of three HSLA steels is studied using the combined techniques of EBSD-KAM and Sub-grain Method. These techniques have been successfully used to assess the annealing behavior of AK, IF and other high strength steels. Stored energy maps in the hot band, cold rolled and after annealing are constructed and analyzed. The combined usage of the Sub-grain Method and EBSD-KAM techniques are employed to calculate and compare the evolution of the stored energy and recrystallization behaviour during the annealing of Ti-bearing, Nb-bearing, and V-bearing HSLA steels. Orientation dependent stored energy distribution maps at different annealing stages are constructed and analysed. The results show that the stored energy distribution through the thickness of the samples is not uniform and is independent of the steel composition. Similarly the recrystallization behaviour is strongly related to the initial microstructural condition and particularly to the grain boundary character distribution of the steels.