Papers by Keyword: Durability

Abstract: Masonry buildings are still very common in the area with high seismic zone, such as the Mediterranean countries and other areas of the world recently hit by earthquakes of considerable intensity. The structural reinforcement of the masonry load-bearing elements is often necessary to increase their seismic resistance, also underway to modern regulatory codes. The use of FRP materials (fiber-reinforced polymers), produced by the pultrusion process, is for these purposes of a possible solutions. FRP pultruded structural elements could enhance the seismic capacity of the reinforced masonry structure and represent an advantage. The application of these materials in the field of structural reinforcement, takes place by gluing with appropriate adhesives or by bolting on the element to be reinforced. The aim of our research is the evaluation of the life cycle (LCA) of FRP glued a halted to the masonry. In detail, the research shows the final experimental results, related to the residual mechanical performance of pultruded samples subject to induced aging.

Abstract: Different initiatives have evolved over the years to improve the durability of concrete, and one of the promising areas gaining attention in recent years is the use of nanomaterials in concrete. Though most of the applications of nanomaterials to improve the properties of concrete has been restricted to laboratory applications, it is anticipated that in few years to come more commercial and large-scale applications will ensue. This overview explored different types of nanomaterials already used in concrete and their effects on the durability of concrete. It was found out that nanosilica is the most used nanomaterial in concrete. And all types of nanomaterials currently used, enhance the durability of concrete significantly compared to other methods employed before the advent of nanomaterials in concrete. However, the use of other nanomaterials such as nanotitania and nanoalumina is attracting great attention. But the use of nanomaterials in concrete is faced by several challenges such as its high cost, production process, toxicity, etc. It is expected that with more research and application in the use of nanomaterials to enhance the properties of concrete, cheap and user-friendly nanomaterials can be developed. In addition, this review shows the possibility of enhancing the current durability properties with the use of nanomaterials.

Abstract: Damage due to atmospheric corrosion on metal structures is a significant aspect for both the design of new constructions and the maintenance of existing buildings. The paper discusses the corrosion depth trends for steel structures comparing an experimental campaign of measurements, given by Fratesi in 2002, with literature 2^nd level models calibrated from experiments on immersed elements, literature models based on testing in atmosphere and standard codes (i.e. EN ISO 9224 and EN 12500). Results show a significant variability of values using different models and codes. In addition, the paper underlines that literature studies and codes neglect specific models for nineteenth-century “wrought iron” constructions, that are very sensitive to corrosion phenomena. Based on this, the paper discusses results obtained by a new interpretative model developed by authors for the prediction of corrosion depth on wrought iron structures.

Abstract: The anode-supported solid oxide fuel cell (SOFC) comprises of NiO-8YSZ | 8YSZ | LSM-GDC | LSCF and the performance durability is executed for over 1000 hours. It shows low degradation phenomena under constant current operation during the complete testing period. The cell performance decreases with the decreasing of the temperature, and the maximum power densities are 408, 265, and 163 mW cm^-2 at 800, 750, and 700 °C, respectively. According to the EIS analysis with the equivalent circuit model of five serial components, all resistances decrease with the testing time except the non-charge transfer resistance of the cathode. However all resistances increase with the decreasing of the temperature on the contrary. The ohmic resistance of the cell (R_O) dominates the cell performance under the whole durability test period as well as the operation temperature. In this study, the R_O is determined by the interfacial contact resistances, which occurred between the cell and the connecting components. The LSM-GDC | LSCF interfaces formed the discontinuous gap due to the weak attachment and external loading. The result of the activation energy analysis shows that the rate-determination step of the cell is existed in the anode side between 700 and 800 °C. However, the cell performance is controlled from the domination of the R_O at 800 °C shift to the joint contributions of the R_O, anodic polarization (R_AP), and cathodic polarization (R_CP) at 700 °C.

Abstract: We reported a superhydrophobic silica-coated surface with a water contact angle of 160° with a 4 μL water droplet, and transparency of 70-86% in the wavelength range of 380-800 nm. The silica film was synthesized at room temperature (22 °C) using sol-gel process by a simple, cost-effective and uniform spin-coating by mixing silicon dioxide sol-gel with γ-(2, 3-epoxypropyloxy) propyltrimethoxysilane (KH-560). The durability of the coating could be effectively enhanced by controlling the ratio of KH-560 and modified silicon dioxide sol-gel. It was believed that this process that we used can hold a great potential in super-hydrophobic surface fabrication.

Abstract: The paper deals with the properties, quality and durability of the exposed concrete. The main part of this paper are characteristic of architectural (sometimes called visible or naked) concrete and the criterion of the quality evaluation of the performed work. This is mainly the colour balance of the subject area, the quantity and the size of the pores, the quality of the raw material and the surface structure. Achieving the quality of architectural concrete is considerably more technologically demanding compared with conventional concrete. This is reflected also in its cost. In conclusion, the problems of surface layers of architectural concrete are summarized. Especially environments can cause faster degradation, reducing the lifetime of the whole construction, but also pointing to one of the main problems in construction, which is technological discipline.

Abstract: Green concrete is a recent sustainable practice in UAE that was enforced by Dubai Municipality in construction field within the emirate of Dubai to reduce the carbon foot print in construction industry and to increase the durability of the structures. This led the construction industry to reduce the usage of ordinary portland cement by replacing it with supplementary cementitious materials (SCMs) such as Grand Granulated Blast Furnace Slag (GGBS) and flyash (FA). Incorporating GGBS or FA in concrete mixtures can improve durability parameters of hardened concrete, such as resistance to water permeability, reduced water absorption and chloride penetration. This ultimately increases the structure’s service life by increasing the threshold of concrete mixture for chloride induced corrosion. On the other hand, carbonation induced corrosion to concrete is usually being ignored or forgotten generally, due its usual slow rate ingression in plain portland cement concrete mixtures. Several studies showed that incorporating some types of SCM – especially at high percentage - can reduce the concrete resistance to carbonation. Additionally and for concrete with recycled aggregate, carbonation investigation should be taken into consideration. This is since recycled aggregates are reused aggregates that are extracted from demolished structures and buildings which were already subjected to different environmental exposures and deteriorations. Unlike chloride penetration, there is no direct ASTM standard test to anticipate the concrete mixture resistance to carbonation at early ages. In this study, concrete mixtures with flyash and different recycled aggregate replacement percentages are investigated for carbonation resistance in accelerated proposed method, considering concrete mixtures’ key parameters like water-cement ratio, and total cement content. The results are analyzed to arrive to pertinent conclusions for the best utilization of sustainable concrete for carbonation resistance.

Abstract: In an effort to reduce the amount of cement in the concrete industry and produce greener concrete, emphasis was put on using several industrial by-products such as silica fume, fly ash and slag as partial replacements for cement in concrete. Due to the enormous number of mega reinforced concrete projects constructed in the United Arab Emirates, it is considered to be one of the largest consumers of high strength concrete in the region. On the other hand, only limited research has been done on high strength concrete incorporating local materials in the UAE. The main objective of this research is to conduct an investigation on the performance of high strength concrete containing silica fume as partial replacement of ordinary Portland cement incorporating superplasticizers and local UAE materials by studying its mechanical properties and durability. The experimental program involved two groups: The first group had a water-to-binder material ratio (w/b) of 0.4, whereas, the second group had w/b = 0.3. For both groups the silica fume replacement percentages were 0 (control mix) 5, 7.5, 10, 12.5, and 15 percent. The mechanical properties were tested at 7, 28, and 91 days and the durability tests were performed at 28 days. The results were compared to the control mix and they showed that for all the curing ages studied the use of silica fume as partial replacement of OPC has favorable effect on the compressive strength values and the optimum replacement ratios of silica fume for the tested specimens are found to be at 12.5% and 10% replacement for the w/b ratios of 0.3 and 0.4, respectively. For all the four performed durability tests the replacement of the OPC with silica fume is found to have favorable results and the higher the silica fume percentage replacement of OPC the more favorable the results are. The detailed description of the used mixes and the main conclusions drawn from this research are presented in this paper

Abstract: The current level of the development of composite materials allows producing laminate structures with the desired properties. The application of supercomputer calculation and software systems, numerical modeling methods using finite elements enables the design and analysis of such structures. This article deals with design and calculation methods; the results of the full-scale tests of the joints of glued laminated timber with carbon fiber dowel pins and plates are presented. An overview of the behavior of such structures in corrosive environment and the comparative analysis with traditional steel components are also presented herein. Advantages and disadvantages of glulam joints where composite materials are used are noted. Examples of the joint use of composi\te materials and timber in Russia and internationally are given. Conclusions about the possibilities and ways of using composite materials in the design of wide-spanned glued timber structures are drawn.

Abstract: Titanium dioxide nanoparticle thin films on the glass slide of 5x20 cm² as substrate were prepared by sparking method. The sparking system was modified by using titanium wires as an anode of 9 pieces and a cathode of 9 pieces which set the gap between the electrodes of 1 mm and connected a high voltage power supply. The sparking method was controlled a surface temperature of substrate as 26, 100 and 150 ^OC and a sparking time of 1-5 h in air atmosphere. The as-deposited thin films were analyzed by a scanning electron microscope, measured the water contact angle of 180 days and studied the durability of thin films on glass substrate to the drop water. The result indicated that the optimum condition of the as-deposited thin films was shown at the sparking time of 4 h and surface temperature of 150 ^OC which shown the homogeneity surface, the hydrophilic properties. The water contact angle increased with increasing the sparking time whereas the increasing surface temperature was found the decreasing of water contact angle. The optimum durability of thin films was used a minimum of a standard deviation (S.D.) at 4.27 which calculated from the water contact angle data from 1-180 days.