Abstract: The present study evaluates the mechanical-microstructural characteristics of the densified high-performance concrete (HPC) incorporating high volume fly ash (FA). The densified mixture design algorithm (DMDA) technology was applied to design the concrete proportions. The effects of various FA contents on both fresh and hardened concrete were investigated. A scanning electron microscope (SEM) was used to observe the microstructure of the concrete samples. The effectiveness of using DMDA in mix deign was also discussed in this study. As the experimental results, the FA content was found to affect the concrete properties significantly. The maximum compressive strength value of 65.1 MPa was obtained at the concrete samples containing 40% FA. Additionally, the 40% FA samples exhibited a denser microstructure as compared to the others. Generally, all of the tested concrete samples exhibited good performance in terms of workability, strength development, water absorption, and porosity. The results of this study further show the effectiveness of using DMDA technology in proportioning of the concrete mixture.
Abstract: Nowadays, on the construction market, there are offered agents for concrete hydrophobization. In most cases, these are preparations that are applied on surfaces of already existing elements. The main disadvantage of such agents are strictly specified conditions, under which they can be applied. It is not recommended to apply the preparations for the elements under water level, exposed to contact with water under pressure, and with visible cracks and scratches [1, 2]. The article presents the results of tests of an innovative agent for concrete hydrophobization that has not disadvantages of the currently applied materials – application of the developed solution takes place at the stage of creating concrete mix. The preparation may be classified as an admixture for concretes.
Abstract: The basic feature characterising the concrete’s quality and its usefulness for a structure is compressive strength. However, other features, such as frost resistance, absorbability, tightness, abrasiveness, decide on the durability of concrete in the structure as well. The paper presents the results of tests conducted on an ecological air entraining agent applied as a concrete mix admixture. The air entrainment of a concrete mix is aimed at entraining additional air pores with appropriate shape, size, and distribution into the concrete structure. The air entrainment is one of the main technological processes aimed at improving the concrete’s resistance to destructive effect of frost [1,2,3,4].
Abstract: A lot of research centres in the world deal with developing the reuse of waste technology. The processed waste is applied in many industries, especially in the infrastructure construction. The European standards allow to apply recycled materials in implementation of buildings and the road engineering. In most cases, the detailed classifications for recycled aggregates are the subject of domestic standards, in which this topic is studied and developed deeply (Germany, Austria). In Poland, at the stage of applying the recycled aggregate, contractors are forced to rely on German or Austrian guidelines. In many cases, the application of the recycled materials is based on the contractors’ experience or intuition. That is why each additional development expansion of the knowledge on the recycled aggregates is added value and is very helpful for designers and contractors. The paper presents the comparison of mechanical resistance to fragmentation in a Los Angeles abrasion machine of selected crushed-stone and recycled aggregates (crushed concrete rubble) from demolished road structures.
Abstract: The long-term durability of concrete hydraulic structures can be improved by controlling their rate of water absorption and linear shrinkage. Incorporation of fibers in concrete composites has the potential to improve these properties of concrete. Artificial fibers are commonly used in concrete due to its durable nature for long serviceable life. So, the overall aim of this research program is to study the effectiveness of artificial fibers for improvement of long-term durability of concrete hydraulic structures. To start with, polypropylene fibers are considered. The polypropylene fibers (PPF) have the unique properties of chemically inertness and low cost raw materials. The pilot study presents the experimental evaluation of water absorption and linear shrinkage of polypropylene fiber reinforced concrete (PPFRC) in comparison to that of plain concrete (PC). The mix design proportion of 1:3:1.5:0.7 (cement:sand:aggregates:water) is used in preparation of PC and PPFRC. For PPFRC, the fiber length of 50 mm and content of 5% by mass of cement are added. All tests are performed as per ASTM standard. Discussions on the considered properties of PC and PPFRC are made. As per expected outcomes PPFRC showed less water absorption and less linear shrinkage as compared to that of PC. Because of this possible attribute, the PPFRC can be used in hydraulic structures.
Abstract: The aim of this study was to synthesize the geopolymer composites formed by two industrial wastes, namely red mud (RM) and saw dust (SD). SD was chemically treated with alkali for the removal of lignin and subsequently bleached, before forming composite with acid-modified RM. The composites were then characterized by using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetic analysis (TGA) and universal testing machine to study the morphology, chemical, thermal and mechanical properties. The FTIR spectrum showed that Si and Al from the raw materials played the major role in forming aluminosilicate geopolymer composites. The SEM images revealed that SD and RM particles aggregated to form fully condensed geopolymer matrices with high compressive strength of 8.3-138 MPa, which were comparable to Portland cement (compressive strength of 9-20.7 MPa).
Abstract: Commonly used waterproofing membranes consist, in over 80%, of bituminous blend. That is why thorough knowledge of factors having impact on the destruction of waterproofing products is of utmost importance. In many cases it is caused by rheological changes, especially ageing processes occurring in bitumen. The purpose of the research is to develop modern solutions that will slow down the processes which occur and thus will extend the life of waterproofing materials. The paper discusses factors affecting the intensity of bitumen ageing and describes physicochemical changes caused by ageing. It also presents test results of bitumen modified with imidazoline which can be used as inhibitors of ageing processes.
Abstract: Metallic material processing plays a significant role in terms of global environmental impact which contributes to the climate change phenomena that is a serious international environmental concern and the subject of much research and debate. Thus, energy-and resource-efficient strategies in the metal shaping technology domain need to be identified urgently. A frequent theme in the debates that surround waste and resources management is the extent to which the recycling of metallic materials offers genuine benefits to the environment. Solid state recycling techniques allow the manufacture of high density aluminum alloy parts directly from production scrap. In this paper the environmental impacts associated with ‘meltless’ scrap processing routes through hot press forging process with varying parameter has been studied. A comparative analysis has been performed, with different operating temperature and holding time of direct recycling hot press forging process AA6061 aluminum chip. The importance of an environmental performance analysis that included both parameter setting was discussed and highlighted throughout the paper. Finally, the application of the proposed parameter setup has resulted in the setting up of an eco-process. Indeed, LCA study on recycling (solid-state) are recommended as well it gives a noteworthy benefit to the environment and to fill the knowledge gap.
Abstract: We choose the optimal cross-sectional shape of the polymer five-lumen catheter products as the goal, and the simulation and experiment of extrusion process parameters were carried out. Firstly, the effect of gas injection pressure and extrusion rate on the extrusion expansion ratio, and the influence of gas injection pressure, extrusion rate and traction speed on the cross-section size, was studied by using Polyflow software; The effects of gas injection pressure, extrusion rate and traction velocity on the five-lumen catheter were studied, the experimental results are compared with the numerical simulation results. The optimal combination of the parameters of the extruded five-lumen catheter is obtained by orthogonal experiment, I.e., the head temperature T = 210 °C, injection pressure P = 4515Pa, the extrusion rate v = 4.5mm / s, pulling speed vp = 33.83mm / s; The corresponding relative error is: Primary lumen relative error Y1 = 3.46%, secondary lumen relative error Y2 = 3.33%, the minimum relative error lumen Y3 = 1%, the outer contour relative error Y0 = 0.61%.
Abstract: This paper establishes a 2D geometrical parameter optimization design method of CMC/metal dovetail joint by using ABAQUS and ISIGHT. Firstly, use the ABAQUS script to finish the 2D geometric parametric modeling and the whole process of the finite element analysis of the simplified dovetail joint in the Python language. Then use ISIGHT software to optimize the 2D geometrical parameters. Finally, compare the optimization results of different optimization methods and get the optimal design parameters. This method is really efficient for the preliminary 2D design of the CMC/metal dovetail.