Lightweight-foamed soils are promising new geomaterials that can be used when the lateral earth pressure and settlement need to be reduced. Lightweight-foamed soil typically consists of dredged ...soils, cement, and air foam. Extra additives could be used to enhance the performance of lightweight-foamed soils, and waste fishing nets are materials that can be used for tensile reinforcement of geomaterials. In this study, a waste fishing net was used in lightweight-foamed soil, and several laboratory tests were conducted to optimize the composition of lightweight-foamed soils in terms of water content, cement ratio, air foam ratio, and net type. A dredged soil in-situ was sampled to use and a waste fishing net was retreated for laboratory experiments. The waste fishing net cut into pieces and some were unthreaded. A form generator was used to produce air foam. The comprehensive evaluation of lightweight-foamed soil reinforced with waste fishing net was performed in terms of the sample preparation time, rheology, unit weight, and strength associated with lightweight-foamed soils. The results showed that lightweight-foamed soils reinforced with waste fishing net provided a peak strength similar with unreinforced one, but having higher critical strength. Finally, the normalized factor (NF) was used to develop a design guideline for lightweight-foamed soils.
This research presents an innovative solution aimed at addressing the cost and accessibility challenges associated with soil stiffness analysis in construction projects. Traditional lightweight ...deflectometer (LWD) systems have limitations due to their high cost and proprietary nature, prompting the need for a more widely accessible technology. To fulfill this purpose, a low-cost, open-source LWD onboard sensor signal interpretation system, utilizing Electro-Mechanical and Micro-Electro-Mechanical-System (MEMS) technology-based sensors in conjunction with an Arduino
Uno and ADS1262 Breakout Board, has been developed. This system efficiently processes raw signal data into deflection and force units, enabling precise soil property analysis. Thorough enhancements, calibration, and alignment procedures have been applied and validated through field tests, which have produced highly satisfactory results. By significantly reducing costs while maintaining accuracy, this developed system has the potential to popularize quality control and assurance practices in the construction industry. This open-source approach not only enhances affordability but also broadens accessibility, making soil property analysis more efficient and attainable for a wider range of construction projects.
The retrofitting of existing RC slabs with an innovative system comprising FRP and HPC has been demonstrated to be effective in strengthening and overcoming the logistical challenges of installation. ...Nonetheless, the excessive improvement of flexural strength over shear strength would cause the sudden failure of rehabilitated flexural members. The literature has previously recommended failure limits to determine the additional moment strength compared with the shear strength to prevent brittle shear failure of strengthened, continuous RC slabs. This study suggests a design process for preventing shear failure and inducing the ductile-failure mode to improve the safety and applicability of retrofitted RC slabs based on the proposed failure limits. The effectiveness of the procedure in brittle-failure prevention for the end and interior spans of retrofitted RC slabs is illustrated via a case study. The outcomes showed that the retrofit system with 0.53-mm-thick-CFRP prevented brittle failure and significantly enhanced the design-factored load and ultimate failure load by up to 2.07 times and 2.13 times, respectively.
In this study, we estimate the potential efficiency of waste fishing net (WFN) fibers as concrete reinforcements. Three WFN fiber concentrations (1, 2, and 3% by volume) were mixed with concrete. ...Compressive strength, toughness, splitting tensile strength, and biaxial flexural tests were conducted. Compressive strength decreased but other properties increased as a function of fiber proportions. According to the mechanical strength observations and the ductility number, WFN fibers yielded benefits in crack arresting that improved the postcracking behavior and transformed concrete from a brittle into a quasi-brittle material. It is inferred that WFN fiber is a recycled and eco-friendly material that can be utilized as potential concrete reinforcement.
The management of plastic waste is a massive challenge and the recycling of plastics for newer applications is a potential solution. This study investigates the feasibility of using polyethylene ...terephthalate (PET) powder in cementitious composites. The changes in the strength and microstructure of Portland cement incorporating PET powder with different replacement ratios were systematically analyzed through the measurements of compressive strength, isothermal calorimetry, X-ray diffraction, thermogravimetric analysis, and Raman spectroscopy. In addition, the possible chemical changes of cement paste samples were studied upon exposure to different conditions, including deionized water, seawater, and simulated pore solution. Based on the test results and analysis, no apparent chemical changes were observed in the cement paste samples, regardless of the exposure conditions. In contrast, the PET powder incorporated into concrete exhibited remarkable changes, which may have occurred during the mixing process. The results also suggested that the maximum replacement ratio of PET powder should be less than 10% of the binder (by mass) to minimize its influence on cement hydration, due to the interaction between water and PET. The PET-containing samples showed the presence of calcium aluminate hydrates which were absent in the neat paste sample.
Three types of connectors were proposed and tested for a modular double-skinned composite tubular (DSCT) wind turbine tower, which is composed of two concentric steel tubes filled with concrete ...between them. The three proposed types were a socket type connector, an H-type connector, and a bolted–welded with shear key connector. Using the proposed connectors, three modular DSCT tower specimens and a single-body specimen were built. Then, quasi-static tests were conducted to evaluate the performance of the three types of connectors, and their behavioral characteristics and failure modes were analyzed. The test results showed that the bolted–welded with shear key connector specimen exerted an almost equal moment resisting capacity as the single-body specimen; however, the other modular specimens exerted only half the moment resisting capacity of the single-body specimen. Moreover, the results showed that the bolted–welded with shear key connector is applicable in a modular DSCT wind turbine tower as it has equal ductility, maximum lateral displacement, and energy dissipation as the single-body specimen.
Supplementary cementitious materials (SCMs) are used to partially replace Portland cement (PC) to reduce the CO2 footprint of concrete. Although many studies have been conducted regarding the uses of ...SCMs as well as oyster shell (OS) with PC, there has been limited investigation into the use of OS coupled with SCMs to replace PC. This study investigated the properties of different types of ternary cement containing OS powder. Ternary cement samples consisting of PC-calcium sulfoaluminate (CSA)-blast furnace slag (BFS) or PC-CSA-metakaolin (MK) were prepared and characterized after 28 and 90 days of curing. The addition of OS formed monocarbonate and hemicarbonate instead of monosulfate, stabilizing ettringite in the samples. As a result, the hydration degree was higher in the CSA-containing samples, whereas the extent of OS consumption was greater in the BFS-containing samples. The results provide new insights into the achievement of an optimal mixture when ternary cements are used with OS.
Although many studies on the blast-resistant performance of structures have focused mainly on single members such as beams and columns, there is little research on the behavior of joints that are ...subjected to blast loads. In this study, the structural behavior of a slab–column connection subjected to blast load was investigated using a numerical analysis method. LS-DYNA was used as a finite element analysis program, and in order to improve the accuracy of numerical analysis, mesh size, material model, and simulation method of blast load were determined through preliminary analysis. The effect of different restraints of the joints, depending on the position of the columns in the slab, on the blast resistance performance was investigated. As a result, the highly confined slab-interior column connection showed better behavior than other edge and corner columns. The drop panel installed between the lower column and the slab was effective in improving the blast-resistance performance of the slab–column connection. For a more accurate evaluation of blast resistance performance, it was suggested that various evaluation factors such as ductility ratio, reinforcing stress, and concrete fracture area can be considered along with the support rotation, which is an important evaluation factor suggested by many standards.
Reprogramming is one of the most essential areas of research in stem cell biology. Despite this importance, the mechanism and correlates of reprogramming remain largely unknown. In this study, we ...investigated the cytoplasmic remodeling and changes in metabolism that occur during reprogramming and differentiation of pluripotent stem cells. Specifically, we examined the cellular organelles of three pluripotent stem cells, embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and epiblast stem cells (EpiSCs), by electron microscopy. We found that the cellular organelles of primed pluripotent EpiSCs were more similar to those of naive pluripotent ESCs and iPSCs than somatic cells. EpiSCs, as well as ESCs and iPSCs, contain large nuclei, poorly developed endoplasmic reticula, and underdeveloped cristae; however, their mitochondria were still mature relative to the mitochondria of ESCs and iPSCs. Next, we differentiated these pluripotent stem cells into neural stem cells (NSCs) in vitro and compared the morphology of organelles. We found that the morphology of organelles of NSCs differentiated from ESCs, iPSCs, and EpiSCs was indistinguishable from brain-derived NSCs. Finally, we examined the changes in energy metabolism that accompanied mitochondrial remodeling during reprogramming and differentiation. We found that the glycolytic activity of ESCs and iPSCs was greater compared with EpiSCs, and that the glycolytic activity of EpiSCs was greater compared with NSCs differentiated from ESCs, iPSCs, and EpiSCs. These results suggest that a change in the cellular state is accompanied by dynamic changes in the morphology of cytoplasmic organelles and corresponding changes in energy metabolism.
This study investigated the effects of seawater exposure on the mechanical, durability, and microstructural properties of cement mortars, which contained silica fume, metakaolin, or glass powder at ...two different replacement ratios. Test variables included the exposure conditions, exposure periods, supplementary cementitious material types, and replacement ratios. Compressive, flexural, and pull-off strengths were measured periodically. Mass change, water absorption, and rapid chloride permeability tests were conducted to evaluate the durability performance of Portland cement mortars (PCMs). Microcomputed tomography was utilized to obtain the pore information from representative PCMs. Test results revealed that seawater exposure yielded positive effects, including flexural strength and durability improvements during short-term exposure periods while those effects might not be last for long period. Metakaolin was the most effective supplementary cementitious material to minimize the reduction in compressive strength, while silica fume contributed to durability improvements. On the other hand, PCM containing GP did not show significant changes in strength and durability. Strong correlations between the flexural strength and durability were observed, and it was explained by additional hydration (i.e., matrix densification) of PCMs (except for the GP) due to the seawater curing which filled specific size of pores ranging 50–200 µm.
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