In recent years, there has been a growing interest in cold asphalt emulsion mixture (CAEM) due to its numerous advantages, including reduced CO2 emissions, energy savings, and improved safety during ...construction and application. However, CAEM has often been considered inferior to hot mix asphalt (HMA) in terms of performance. To address this issue and achieve desirable performance characteristics, researchers have been exploring the modification of CAEM using high-cost additives like ordinary Portland cement. In this study, the focus was on investigating the effects of utilizing waste alkaline Ca(OH)2 solution, ground granulated blast-furnace slag (GGBFS), and calcium carbide residue (CCR) as modifiers to enhance the properties of CAEM. The aim was to develop an innovative geopolymer geopolymer-based cold asphalt emulsion mixture (GCAE). The results of the study revealed that the use of waste alkaline Ca(OH)2 solution led to an increase in early hydration, which was confirmed through scanning electron microscopy. Furthermore, the experimental findings demonstrated that waste alkaline Ca(OH)2 solution significantly contributed to the rapid development of early-age strength in GCAE. As a result, GCAE showed great potential for utilization in pavement applications, particularly for roads subjected to harsh service conditions involving moisture and temperature. By exploring these alternative modifiers, the study highlights a promising avenue for enhancing the performance of CAEM and potentially reducing the reliance on expensive additives like ordinary Portland cement. The development of GCAE has the potential to offer improved performance and durability in pavement applications, thus contributing to sustainable and efficient road infrastructure.
In order to determine the ideal degree of inclination that should be employed for constructing effective thermal energy storage systems, it is important to examine the impact of inclination angle on ...the melting behavior of phase change materials (PCMs) such as paraffin wax within a square cell. In consequence, this would guarantee the greatest capacity for energy release and storage. Additionally, analyzing this influence aids engineers in creating systems that enhance heat flow from external sources to the PCM and vice versa. To find out how the cell's inclination angle affects the melting of PCM of paraffin wax (RT42) inside a square cell, a numerical analysis is carried out using the ANSYS/FLUENT 16 software. Specifically, the temperature and velocity distributions, together with the evolution of the melting process, will be shown for various inclination angles, and a thorough comparison will be made to assess the influence of inclination angle on the PCM melting process and its completion. The findings demonstrated that when the cell's inclination angle increased from 0° to 15° and from 0° to 30° and 45°, respectively, the amount of time required to finish the melting process increased by 15%, 42%, and 71%, respectively. Additionally, after 210 min of operation, the PCM's maximum temperature is 351.5 K with a 0° angle of inclination (horizontal) against 332.5 K with an angle of inclination of 45°.
Semiflexible pavement (SFP) is considered a composite mixture, as it consists mainly of a porous asphalt mixture with high air voids grouted with highly flowed cementitious grout. Numerous benefits ...have been attributed to this technology, including exceptional slip resistance, a high static bearing capacity, and rutting resistance. In this study, two different types of semiflexible paving mix were produced by using two different types of grouting materials (GMs). There is a discrepancy between the compressive strengths of the two GMs used, as the compressive strength of the first mixture, which consisted of 96% cement and 4% silica fume (SF), was approximately twice the compressive strength of the second mixture, which consisted of 75% cement and 25% sand. The mechanical and durable properties of the two SFPs were studied, in addition to the effect of variation in the compressive strengths of the two GMs and their effect on the final performance of the pavement. The results of Marshall and rutting tests show that the SFP material exhibits good high-temperature stability. The effect of the variation in the compressive strength of the two mixtures was evident in the results of the tests compared with the sand mixture at a strength of 20.8 MPa, the SF at a strength of 48.1 MPa witnessed a 39.54% increase in the Marshall stability at 28-day curing age. Also, the composite material (CM) showed better rutting performance than traditional asphalt mixtures, which did not exceed 2 mm. The results of the indirect tensile strength (ITS) test showed a discrepancy between the two types of CM, as the ITS value of the grouting material of SF (GMSF) mixture increased by 14.91% compared with the grouting material of sand (GMSN) for the curing age of 28 days for unconditioned samples and by 20.22% for the conditioned samples for the same curing age, while the durability of two types of CM was measured by Cantabro abrasion loss and tensile strength ratio. The results were acceptable and within the specification limits. With a variation for the two types of CM, the GMSF mixture showed an increase in the value of Cantabro loss by 11.52% over the GMSN mixture for ageing samples and 6.59% for non-aging samples of 28 days of curing age.
Researchers have been driven to investigate sustainable alternatives to cement production, such as geopolymers, due to the impact of global warming and climate change resulting from greenhouse gas ...emissions. Currently, they are exploring different methods and waste materials to enhance the mechanical and physical properties of geopolymer and expand its application range. This review paper offers a thorough analysis of the utilization of various waste materials in geopolymer manufacturing and shows the creative contribution of this research to the development of environmentally friendly cement substitutes. The article covers the properties, durability, and practical applications of geopolymer composites made from various waste binders. It includes a microstructure and chemical analysis. The research findings indicate that geopolymers are an effective cementitious binder substitute for cement in various applications. Additionally, the ecological and carbon footprint analysis highlights the sustainability of geopolymers compared to cement.
The present experimental work briefly aimed to utilize two different waste materials; calcium carbide residue (CCR) and the locally available rice husk ash (RHA) to produce an eco-friendly binder for ...the use in fine-grained soil stabilization. The effect of different binary mixtures, produced by mixing CCR and RHA with different proportion, on the geotechnical properties of a fine-grained soil was investigated. For the unconfined compressive strength (UCS) test, the soil specimens were subjected to various curing periods (7, 21, 28 and 90 days). The microstructure of the soil treated with the optimum mixture was carried out by utilizing scanning electron microscopy (SEM) test. Results of UCS test showed an interesting growth after the treatment of binary mixtures relative to those samples treated with only CCR. Plasticity index (PI) was found to decrease noticeably with use of CCR only while further reductions in PI were achieved after the RHA incorporation. Clear variations in the microstructure of the treated soil were revealed from SEM testing approving the creation of cementitious products. The results of the current study indicated that the wastes utilized in this investigation could be potentially used as alternatives to the conventional binders and final disposition with economic and environmental advantages.
Waste ceramic is produced from different sources and, if not reused, is often disposed of in landfills, contributing to the pressure on landfill capacity and potentially releasing toxins into the ...surrounding environment as ceramics break down over time. The waste can easily be crushed to the required sizes, which has interested many researchers. It has been used as a replacement for concrete constituents, including cement and aggregates. This offers a promising avenue for reducing the environmental impact and promoting sustainable construction practices by reducing the amount of energy consumed and resources required for concrete production, as well as the amount of waste being sent to landfills. This paper aims to provide a review of the use of waste ceramic in concrete. In essence, the paper is divided into several sections. The first section highlights the current environmental issues associated with concrete production and waste disposal. The second section deals with ceramics, its raw materials, production steps, and the different types of waste ceramic used in concrete. A literature review of the use of waste ceramic in concrete was included in the third section. The study reports different research on the use of waste ceramic and its impacts on the mechanical and durability properties of concrete.
The efficacy of a pavement system is significantly influenced by the condition of the road pavement. Improving pavement quality is essentially the key to reducing problems with fatigue cracks and ...rutting on roads. One of its tenets is changing and enhancing asphalt’s performance by use of various additives. One of the plastics having the highest recycling rates across various nations is polyethylene terephthalate, or PET. Since virgin PET (V-PET) and recycled PET (R-PET) cannot currently be analytically separated from one another, numerous indirect approaches have been developed to achieve this. According to one idea, recycling PET causes polymer chains to break, which alters the material’s structural, mechanical, and thermal characteristics. R-PET and V-PET can therefore be distinguished from one another. Temperature and load stress cause asphalt pavement damage, especially rutting. In order to reduce the issue of road rutting, several measures have been implemented, such as enhancing the quality of pavement and improving the procedures used for structural design. In recent years, engineers have shown a growing interest in enhancing the performance of asphalt by incorporating various additives and substituting raw materials with virgin and recycled materials. This approach aims to improve environmental sustainability and reduce the cost of modified pavement mixtures. The purpose of the study is to assess the effect of modifying bitumen of grade 40–50 with V-PET. This study examined the use of V-PET as an asphalt modifier, at varying concentrations of 1, 2, and 4% by weight of asphalt. The study aimed to assess the influence of these concentrations on the performance of asphalt under high temperature conditions. The results demonstrated that the addition of 2% V-PET to the asphalt binder significantly improved the characteristics of the asphalt, resulting in increased resistance to rutting in the pavement.
The influence of styrene butadiene rubber (SBR) or low-density polyethylene (LDPE) polymers on the characteristics of local asphalt binder was analyzed to characterize the rheological properties. The ...results indicated that the SBR or LDPE increased the softening point. The softening point was enhanced by around 35% when 9% of SBR was used in comparison to the unmodified asphalt, while there was a 15% increment when LDPE was used. The results also indicated that the SBR or LDPE decreased the penetration rate. The penetration decreases by around 36% when 9% of SBR is used compared to the neat asphalt, while a significant increment was 89% when 9% of LDPE is used. Additionally, when 9% SBR was employed, the ductility of the asphalt binder rose by roughly 73%, but 64% less ductility was seen when 9% LDPE was utilized. Finally, the addition of the additive has improved the penetration index, thus reducing the temperature sensitivity. Due to said above, SBR and LDPE are practical and promising modifiers that will be useful in enhancing the performance of the asphalt binder straightforwardly and efficiently.
Numerous heating and cooling design methods, including energy storage, geothermal resources, heaters, solar collectors, underground water movement, lakes, and nuclear reactors, require the study of ...flow regimes in a cavity and their impact on thermal efficiency in heat transportation. Despite the existence of several review studies in the open literature, there is no specific review of heat transfer investigations that consider different cavity designs, such as spheres, squares, trapezoids, and triangles. Therefore, this work aims to conduct a comprehensive review of previous research published between 2016 and 2023 on heat transfer analysis in these cavity designs. The intention is to clarify how various cavity shapes perform in terms of flow and heat transfer, both with and without the addition of nano-enhanced phase change materials (NePCMs), which may include fins, obstacles, cylinders, and baffles. The study also explores the influence of factors like thermophoresis, buoyancy, magnetic forces, and others on heat transport in cavities. Additionally, it investigates the role of air, water, nanofluids, and hybrid nanofluids within cavities. According to the reviewed research, nanoparticles in the base fluid speed up the cooling process and reduce the required discharging time. Thermophoresis, where nanoparticles move from the heated wall to the cold nanofluid flow, becomes more pronounced with increasing Reynolds numbers. Increasing the heated area of the lower flat fin enhances the heat transfer rate, while increasing both the Rayleigh number and the solid volume percentage of nanoparticles reduces it. Radiation blockage alters the path of hot particles and affects the anticipated radiative amount. Optical thickness plays a role in rapidly cooling a medium, and partition thickness has the most significant effect on heat transport when the thermal conductivity ratio is low. Heat transmission is most improved when the Rayleigh number is high and the Richardson number is low.
Due to its significant deficiencies such as low permeability, low bearing and shear strength, and excessive compressibility, soft soil is one of the most problematic types of soil in civil ...engineering and soil stabilization can be considered a suitable technique for pavements. This study investigates the use of ground granulated blast slag (GGBS) and cement kiln dust (CKD) as stabilizers for soft soil. Thus, this study involves two optimization stages; in the first stage, GGBS was incorporated into 0%, 3%, 6%, 9%, and 12% by the weight of cement to obtain the optimal percentage, which was 6%. Then, the optimal GGBS was blended with CKD in a binary system at 0%, 25%, 50%, 75%, and 100% by the dry weight of the soil. The testing program used in this paper was Atterberg limits with compaction parameters to investigate the physical properties and unconfined compressive strength (USC) at 7 and 28 days to examine the mechanical characteristics. In addition, the microstructures of the soil specimens were tested at 7 and 28 days using scanning electron microscopy (SEM). The findings reveal that the binary system enhanced the physical and mechanical properties of the soft soil. The optimum binder achieved in this study was 6% (25% GGBS and 75% CKD), which generates an increase in strength of about 3.3 times in 7 days, and of 5.5 times in 28 days in comparison to the untreated soil. The enhancement was attributed to the formation of the hydration products as approved by SEM. Consequently, in the case of soft subgrade soils, this technique can increase the pavement’s bearing capacity and performance.
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