Key Engineering Materials Vol. 913

Abstract: Biochar research has been gaining recent interest in agricultural applications because of its use as a soil amendment. Biochar is a porous carbonaceous solid produced from heat in the absence of any introduced oxygen (pyrolysis). It has relatively high surface area and slow-release properties that makes it suitable for fertilizer formulation. In this study, rice straw is used for biochar production using modified carbonizer at 600-650°C temperature range. After synthesis in the nanoscale level, the biochar produced was infused with nutrients such as nitrogen, phosphorus, potassium and zinc. The morphological characteristics were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and energy dispersive Xray spectrometry (EDS). Nutrients were incorporated in the biochar and analysis revealed concentrations of 4.96% N, 3.46% P, 2.25% K, and 10.90% OM. The nanoscale biochar-based fertilizer was then applied into rice production. Rice grown in soil amended with nanoscale biochar-based fertilizer showed higher yield than control treatments but with comparable result from the inorganic fertilizer treatments. This implies that biochar can be used as an alternative to chemical based fertilizer when infused with the essential nutrients needed by plants. Furthermore, the soil amended with the nanoscale biochar-based fertilizer was also found to have a higher nutrient and organic matter content after harvest. Therefore, it could preserve the soil fertility which is beneficial in the long term.

Abstract: Adobe is a building material that has been used since ancient times, but is not as widely used as clay bricks or concrete for housing construction. In addition, it uses a construction technique that has been passed down and improved from generation to generation. In view of this, the present work aims to improve the properties of adobe by using PET bottle fibers in its composition. A mechanical test and two physical tests were carried out for adobe with 0% (standard adobe), 2%, 4% and 6% PET fibers, where it was observed that the adobe with 6% PET fibers obtained the best results, since it increased the compressive strength of the adobe by 19%, reduced the absorption percentage by 12% and finally reduced the density by 16.4%. Therefore, the addition of PET fibers in adobe is recommended, as it contributes to improve its mechanical and physical properties. Additionally, it reduces pollution in streets, rivers, parks, etc. because it promotes the recycling of PET bottles.

Abstract: At present, the amount of organic wastes including banana stem and corn husk produced from the Philippines is roughly 56 million technical tons. On the other hand, the construction industry demands innovation to some of the construction materials including cement fiber boards (CFB). The objective of this study is to address the increasing volume of organic wastes including banana stem and corn husk (BSCH) by incorporating BSCH fibers in to cement boards. To test whether the boards fabricated with BSCH fibers is a viable option, the study determined the physical and mechanical properties of cement boards reinforced with BSCH fibers added with citric acid. The experimental results obtained from this study showed that the flexural strength of the cement boards reinforced with banana stem and corn husk fibers is higher than the cement boards without fibers. On the other hand, the compressive strength the cement fiber boards increased in 8% fiber reinforcement and gradually decreased as more fibers were added to the mix. Furthermore, the boards with fibers showed effective drilling characteristics. From the tested cement fiber boards, the cement fiber boards with 8% fiber reinforcement showed the most promising results in both physical and mechanical properties of the fiber cement board.

Abstract: The recycling of construction and demolition waste (CDW) is currently of growing interest. Starting from such waste products it’s possible to produce recycled aggregates for construction purposes providing environmental and economic advantages. Life-cycle assessment (LCA) is a valuable tool to evaluate the environmental impact at end of life of CDW and improve the employment of recycled aggregates in concrete. In this research a life cycle evaluation of concrete mixtures made with CDW is performed to assess their environmental impacts considering various scenarios related to recycling sites with different conveying distances. The advantages of replacing natural aggregates with recycled ones are evaluated using a combination of LCA model and Life-Cycle Impact Assessment to estimate the environmental effects for all the considered scenarios. The results highlighted the highest environmental impact for the scenario with total landfill as well as an increasing impact for increasing distance from the demolition site.

Abstract: Every year, in the world, the produced quantities of plastic amount to approximately 400 million tons. This implies a high level of plastic pollution and a growing decrease of available natural resources. Therefore, seems to be clear that there is a need to act in such a way as to reduce plastic pollution, safeguard natural resources and prevent the disposition of great quantities of waste in landfills or, even worse, the discharging into marine waters. This explains the need to implement processes of recovery and recycling of this plastic waste and their reuse in operable and practical products. Many studies analyzed the chances of employing plastic waste to produce cement and concrete, but the research about the use of polyolefins for the production of lightweight concretes is still limited. This study shows that the use of recycled polyolefins as substitutes of natural aggregates is a viable solution for the production of lightweight concretes by analyzing the influence of this kind of plastic on mechanical, physical and thermal performance, through experimental tests performed on four samples containing different amounts of plastic aggregates.

Abstract: The production of lightweight artificial aggregates proposed in this study derives from industrial waste recovery activities, such as fly ash (FA) and ground granulated blast furnace slag. The aim is to reduce the compromise of the environment and human health, through the recycling of special waste. The use of inert aggregates from recovery from industrial waste encourages the reduction of soil consumption, the waste of natural aggregates, consequently limiting the consumption of waste materials from quarries, as well as facilitating the recovery of waste that would inevitably end up in landfilled or abandoned in the environment. Specifically, in the present work, the lightweight artificial aggregates were produced by cold bonding granulation technique. All the mixtures, made by 80% of FA with various composition of cement and granulated blast furnace slag, were characterized by density values ranging from 1.63 to 1.66 g cm-3 suggesting their suitable classification as lightweight aggregates (LWAs). Water absorption capacity (WAC) and open porosity values decreased with the increase of the percentage in cement. The impact test results indicate that all the aggregates have proved to be suitable as filling for road pavements. The best crushing strength values (1.86 MPa) were observed for the mixture contain the highest amount of cement. Aggregate leaching tests indicated a significant release of chlorides and sulphates while the release of heavy metals was lower than the limits set by the standard UNI 10802.

Abstract: For ages, natural fibers have been used as building materials. In the last centuries the man-made fibers, steel and concrete have predominantly dominated construction sector. Climate change has highlighted the importance of sustainable construction that can reduce the carbon footprint and the application of green, natural, recyclable and sustainable. In this work, the chemical composition and the effectiveness of jute fibers used as reinforcement in thermal and structural mortars. Therefore, the physical properties of both jute fiber and composite were determined by Scanning Electronic Microscope (SEM), which show a good compact microstructure in case of structural mortar and bonding inhomogeneity in case of thermal mortar. The fibers improved ductility of the mortars, yet reducing their flexural and compressive strengths.

Abstract: Sawdust materials are important for several reasons. They are cheap, lightweight, and have high insulation properties. Some of this material is incorporated into the concrete as part of the cement binder phase and as gravel. Micro-cracks and defects in concrete are responsible for the low tensile strength of concrete. This study proposes the use of sawdust as a partial replacement for fine aggregate. By volume, the sawdust gradually replaced the sand with a replacement percentage that varied from 0% to 100%. Nine reinforced concrete beams with a cross-section of 90 mm × 150 mm × 1000 mm (width × depth × length) and different replacement percentages were cast and tested after 28 days. All concrete beams are supported, with two simple supports at the ends of the beam and a loading point at the center of the beam to apply load gradually using 100 kN load cells and transverse frames. The addition of sawdust results in a reduction in the flexural strength of concrete beams. The flexural reinforced concrete beam test results were compared to the design strength calculated using British Standards. According to the results of the study, both the compressive and tensile strength of concrete decreased as sawdust content increased. The weight of the sawdust concrete mixture decreased with increased sawdust content. When the replacement percentage of sand was between 5% and 20%, the sawdust concrete mixture showed good results for the structural performance of the reinforced concrete beam.

Abstract: Self-compacting concrete (SCC) is a type of concrete that does not require vibration and undergoes compaction under its own self-weight. Cement being the major constituent of self-compacting concrete is very expensive. Thereby incorporating fly ash, a by-product obtained by burning coal in coal power plants, the percentage of cement can be reduced. Thus in this study, class C fly ash in varying percentages from 0 to 30% has been used as a partial replacement of cement. The main purpose is to study the effects of fly ash on mechanical behavior and durability properties of self-compacting concrete and to choose the optimum dosage of fly ash. To determine the mechanical behavior, fresh properties of self-compacting concrete were studied by performing Slump flow, J-ring, V-funnel, and L-box tests. Hardened properties were evaluated by performing the Compressive strength and Split tensile test. The durability was determined using the volume of voids and sorptivity test. Tests to study mechanical behavior were performed by casting cylinder, whereas, concrete discs were cast to perform durability tests. Finally, it was observed that the replacement of 25% Fly ash with cement was found to be the optimum percentage.

Abstract: Traditionally stone architecture has been built in the Dhofar region in Southern Oman. However, modernization policies under the reign of Sultan Qaboos since the 1970s have led to the replacement of traditional building materials with industrial ones. As research on the manufacturing methods and usage of traditional materials is limited, many buildings are at risk of disappearing. This study aims to clarify the functions and properties of the three principal materials, khatri, nurah, and yeb', used as both joint and finishing materials in the coastal areas of Dhofar. According to interviews with local traditional masons, khatri is used as a joint and wall-finishing material, nurah as a wall-finishing material, and yeb' as a floor-finishing material. Particle-size tests revealed that the particles become finer in the order of: khatri, nurah, and yeb'. Furthermore, XRF and XRD reveal that nurah had a higher calcium content compared to khatri and yeb'. The combination of interviews and engineering experiments indicate that the manner in which local masons use these three materials is highly dependent on their physical properties. This can be reasonably explained based on the climate: Dhofar experiences more rainfall than Northern Oman during summers. These findings can aid in the improvement and continuous use of traditional building materials and contribute to a sustainability.