Papers by Keyword: Durability

Abstract: The present research study is an effort to evaluate the effect of different nanoparticles in lime-pozzolan system, in time. nanosilica, nanoalumina and nanocalcium oxide were used in different combinations in this traditional binding system. The paper aims to record the durability of the traditional binding system in time, up to 365 days. For that purpose, the samples were subjected to ageing tests, such as wetting-drying cycles, sea water cycles and salt cycles. Up to 90 days, nanosilica benefits the most of the physic-mechanical properties, as well as the microstructure. Though, by studying the systems in time, the behavior of the other nanoparticles seems to favor certain properties more than nanosilica, especially at later ages. The addition of nanocalcium oxide combined with nanoalumina aids the improvement of the microstructure and the system presented great compressive after 40 cycles in ageing tests.

Abstract: The main objective of this case study is to compare whether standardized test methods are able reliably prognosticate the performance of joint sealants and adhesives after installation in a construction. The authors of presented study believe that existing testing procedures intended for testing of bonded and sealed joints do not fully reflect the weather changes exterior surfaces have to withstand. Based on previous experiences a unique geometry of testing sample was used for this purpose allowing the testing of a so-called real joint. A group of test samples was subjected to two normalized test procedures that may influence the resulting behavior of the joint in the exterior. The second group of test samples was exposed to the external environment for a particular period. The obtained results of tests show that the standardized methods are able to simulate an outdoor environment, however, only to a certain level. Unfortunately, these methods do not consider the possibility that the sealed or bonded joint might be damaged already during the application itself. While laboratory environment is clean and often dust free, it is not possible to ensure the same conditions in situ. Moreover, in some cases it was monitored that some of the selected sealants tested in an external environment aged rapidly compared to the ones cured and stored in the laboratory. In some cases, the difference between monitored failure modes for indoor and outdoor environment was substantial. The predominant type of sealant failure observed in-situ was adhesive while mainly cohesive failure was monitored in laboratory.

Abstract: The paper presents the experimental results of the possible use of the type 2024-T351 aluminum alloy for manufacturing the ball bearing rings of the rotary support system of the calibration equipment for magnetometric inclinometers. Non-magnetic materials for ball bearing manufacturing are reviewed. The description is given to the test equipment and procedures. The experimental results demonstrate that the type 2024-T351 aluminum alloy can be used for manufacturing a tailor-made ball bearing of the rotary support system. Stresses arising in the contact area do not exceed the allowable values of s_max £ (0.3–0.5)s_0,2.

Abstract: The use of dehydrated fibres of cactus, Opuntia ficus-indica (FN), and starch (corn starch,Zea Mays (MZ)) as partial substitutes for the total mass of Portland Cement (CP) in the making ofmortar, aims at modifying its physical and mechanical properties, reducing the amount of cementand the CO2 emission. Four mixtures of CP mortar were designed incorporating a superplasticizeradditive with a water/cement weight ratio of 0.68. To compare the results, there was a controlmortar; two mixtures with partial substitutions using fibres of FN, 0.5 and 1.5% (in weight of CP)respectively; and a substituted mixture with 2% of corn starch plus 0.5% of cactus fibre (MZ - FN).The test age was 180 days. The specimens were subjected to an accelerated attack of sodiumsulphate, quantifying the electric resistivity (ER) and the ultrasonic pulse velocity (UPV). Theresults indicate that the substitution of the materials, remarkably densify the cement matrix, whichresults in the improvement of the physical properties and the durability.

Abstract: The wettability and durability of Si-O coatings prepared on zirconia substrate using radiofrequency magnetron sputtering (rf-sputtering) was studied. XRD analysis revealed no phase transformation of zirconia before/after rf-sputtering process. XPS spectroscopy showed that as-deposited films with a SiO₂ configuration was formed. EDX analysis indicated that the Si/Zr ratio was high and when magnetron rf-sputtering was performed using a plasma gas Ar+5% O₂, which may be the optimum condition of rf-sputtering to form a sustainable hydrophilic layer on zirconia substrate. The wear testing using pin on disc wear apparatus was performed. The wettability and durability of Si-O coatings fabricated by magnetron radiofrequency magnetron sputtering (rf-sputtering) on zirconia substrate was studied. A plasma gas Ar+5% O₂ may be the optimum condition of rf-sputtering to form a sustainable hydrophilic layer on zirconia substrate

Abstract: Premature deterioration of reinforced concrete structures due to corrosion of the reinforcing steel is a major concern worldwide. In this study code provisions and design considerations for using corrosion resistant reinforcing steel bars have been discussed at length. The most common corrosion resistant reinforcing bars available today are– Fusion Bonded Epoxy Coated Bars (ASTM A775), Hot Dip Galvanized Steel Bar (ASTMA767), Glass Fiber Reinforced ,Polymer Bars and Stainless Steel Rebars (ASTM A955). Especially in marine environments corrosion of reinforcement is one the major concerns regarding durability of RC Structures. Also parts of any structure that are subjected to intermittent wetting and drying (e.g. bridge piers) and those that are subjected to dampness (e.g. topmost roof slab of a building) are more susceptible to corrosion. It is well known that Bangladesh’s already struggling infrastructure is under a constant threat of deterioration due to various physical and environmental conditions while a huge shortfall in budget exists to ensure periodic maintenance and repair works. Corrosion resistant rebars are globally accepted corrosion resistant system that will ensure the structures can be used till the end of their design lives. While demand for all non-corroding bars is on the rise, expertise of engineers and construction workers in handling these bars should grow as well. Therefore recommended work practices while manufacturing, fabricating and concreting has to be included in the country’s standards and guidelines.

Abstract: The structure and properties of the cemented products from steel 20H2N4A strengthened according to different schemes of chemical heat treatment is investigated. The reason of low static and cyclic firmness of parts is established. The new technology of hardening of parts which is based on application of low-temperature cementation is developed and offered. For a steel saturation process of intensification with carbon it is recommended to increase the content of hydrogen to 40% in the endoatmosphere and to enter a small amount of ammonia into the saturating atmosphere of the furnace.

Abstract: The investigations carried out in the field of creation of large-size crack-resistant structures and cellular concrete products have shown that this problem is multifaceted and it must be solved in a complex manner, and one of the ways to increase the crack resistance and durability of such structures and products is prestressed reinforcement.

Abstract: Concrete on Portland cement and cement modified with expanding additives were studied. The authors present the results of study of the modified concrete with combined aggregate. Combined aggregate is a composition of natural granite and limestone crushed stone mixed with crushed concrete. Structure and properties of concrete with combined aggregate is insufficiently studied, which limits their use in civil engineering Recycling of building materials allows to expand the raw material base, to solve the problems of resource conservation and environmental protection. The regularities and causes of changes (reduction) indicators of the quality of concrete with combined aggregate. Studying of properties and laws of formation of structure of concrete at the same time is a method of control of their production. The valuation of properties of concrete with combined aggregates will allow to use them along with traditional concrete.

Abstract: Reinforced concrete conical structures are the basis of safety and operational reliability of railways power supply systems. The article presents optimal methods for diagnostics of reinforced concrete structures, which allow recommending the sequence and amount of repair work aimed at restoring or maintaining the required state of reinforced concrete conical section structures (contact-line supports, power transmission line supports, etc.). A design scheme is proposed for determining the residual bearing capacity of the support in the presence of cracks and corrosion of the reinforcement.