B. Saleh, Ayman A. Aly, M. Alsehli, M.M. Bassuoni and A. Elfasakhany
This paper aims to investigate the performance and working fluids screening for an ejector refrigeration cycle (ERC) activated by solar energy. Several common and new…
Abstract
Purpose
This paper aims to investigate the performance and working fluids screening for an ejector refrigeration cycle (ERC) activated by solar energy. Several common and new hydrofluorocarbons, hydrocarbons, hydrofluoroolefins and hydrofluoroethers are proposed as refrigerants for the ERC to determine the most appropriate one.
Design/methodology/approach
The ejector performance is characterized by the ejector area ratio (EAR) and entrainment ratio (ω), while the cycle performance is described by the coefficient of performance (COP). The influences of many working parameters like the evaporator, condenser and generator temperatures on the ejector and cycle performances are investigated for all candidates as well.
Findings
The results indicate that the best ejector and cycle performances are attained with the highest critical temperature dry refrigerant, i.e. R601 under all studied working conditions. From the perspective of energy efficiency and environmental issues, R601 can be considered the most appropriate working fluid amongst all candidates. However, extra attention should be considered against its flammability. The maximum COP, the corresponding ω and the necessary EAR using R601 are 0.743, 1.02 and 15.5, respectively, with 25 ºC condenser temperature and the typical values for the rest operating conditions.
Originality/value
Many common and new hydrofluorocarbons, hydrocarbons, hydrofluoroolefins and hydrofluoroethers are suggested as working fluids for the ERC to determine the most appropriate one. The mixing process inside the ejector constant-area section is assumed constant-pressure process.
Details
Keywords
Duc-Hoc Tran and Putri Basenda Tarigan
The concept of sustainability is about the relationships among people, the planet, and profit. Nowadays, it has been spread to many areas, including construction projects…
Abstract
The concept of sustainability is about the relationships among people, the planet, and profit. Nowadays, it has been spread to many areas, including construction projects. Sustainability in construction projects has been so important in the present time. It is commonly pointed to the environment and construction materials. Nevertheless, it is also important in construction management which addresses sustainable project scheduling. Sustainable project scheduling will help to deliver the project under the deadlines, within the available budget, and also ensuring about the quality of the works. This study presents the trade-off among time, cost, and quality in the construction project to provide the decision-maker some alternative solutions in the planning phase to conduct a sustainable construction project. Multi-objective optimisation using Symbiotic Organism Search (SOS) algorithm is done to find the best solutions to the problem under investigation. Then, fuzzy logic approach is utilised to model the diverse environment and uncertainty in the construction project. A case study in repetitive construction project is analysed to see the capability of the model to work in time cost quality trade-off to reach into a sustainable construction project.
Details
Keywords
Djoual Belkacem, Mitiche-Kettab Ratiba and Zaitri Rebih
The study aimed to explore the effects of mineral admixtures – especially limestone filler (LF), brick powder (BP) and ceramic powder (CP) – on the performance of self-compacting…
Abstract
Purpose
The study aimed to explore the effects of mineral admixtures – especially limestone filler (LF), brick powder (BP) and ceramic powder (CP) – on the performance of self-compacting sand concrete (SCSC). It studies their effect on mechanical properties and mass loss when exposed to acidic solutions (H2SO4 5% and HCl 5%) over periods of 28, 90 and 180 days. The study seeks to develop SCSC technology by taking advantage of locally available sand resources.
Design/methodology/approach
Using an experimental design, the study explores different formulation parameters, including the use of silty sand (AS) and dune sand (DS) in fixed proportions, where AS constitutes 70% and DS 30% of the total sand content. The superplasticizer ratio (SP) and water-to-binder ratio (W/B) are constant with varying amounts of mineral additives. The study immerses SCSC samples in acidic solutions (5% H2SO4 and 5% HCl) for 28, 90, and 180 days to evaluate mass loss and mechanical properties. This endeavor to advance such concrete technology is motivated by the desire to incorporate sand concrete into the realm of self-compacting concrete technology while also harnessing the advantages of locally available sand resources, particularly dune sand, which is abundant in the southern regions of Algeria.
Findings
SCSC results with mineral additives showed enhanced resistance in both tensile and compression tests, indicating improved durability compared to the reference sample without additives. However, excessive proportions of BP (>60%) or CP led to exceptions in this trend An exception to this trend was observed when BP was added in proportions exceeding 60% or when CP, indicating potential limitations in some additive formulations. Overall, the research provides valuable insights into improving the performance and durability of SCSC through the strategic incorporation of mineral admixtures, contributing to advances in self-compacting concrete technology.
Originality/value
1 – Valorization of local materials and recycling of waste: DS, LF, BP and CP, which are available in great quantities in the south of Algeria; 2 – Combination, at the same time, of alluvial sand and dune sand as aggregate and LF, BP and CP as filler. 3 – Application of the design of experiments method methodology for the optimization of these elements of the new sand concrete studied. The new building material elaborated present indeed a technical, economic and environmental interest.
Details
Keywords
Taha Hocine Douara, Salim Guettala, Tarek Hadji and Ahmed Attia
The purpose of this study is to contribute with experimental study of the effects of binary and ternary combinations of river sand (RS), crushed sand (CS) and dune sand (DS) on…
Abstract
Purpose
The purpose of this study is to contribute with experimental study of the effects of binary and ternary combinations of river sand (RS), crushed sand (CS) and dune sand (DS) on the physical and mechanical performances of self-compacting concrete (SCC) subjected to acidic curing environments, HCl and H2SO4 solutions.
Design/methodology/approach
Five SCCs were prepared with the combinations 100% RS, 0.8RS + 0.2CS, 0.6RS + 0.2CS + 0.2DS, 0.6RS + 0.4DS and 0.6CS + 0.4DS. The porosity of sand, fluidity, deformability, stability, compressive strength and sorptivity coefficient were tested. SCCs cubic specimens with a side length of 10 cm were submerged in HCl and H2SO4 acids, wherein the concentration was 5%, for periods of 28, 90 and 180 days. The resistance to acid attack was evaluated by visual examination, mass loss and compressive strength loss.
Findings
The results showed that it is possible to partially substitute the RS with CS and DS in the SCC, without strongly affecting the fluidity, deformability, stability, compressive strength and durability against HCl and H2SO4 attack. The two combinations, 0.8RS + 0.2CS and 0.6RS + 0.2CS + 0.2DS, improved the compactness and the resistance to acid attacks of SCC. Consequently, the improvement in SCC compactness, by the combination of RS, CS and DS, decreased the sorptivity coefficient of SCC and increased its resistance to acid attacks, in comparison with that made only by RS.
Originality/value
The use of RS is experiencing a considerable increase in line with the development of the country. To satisfy this demand, it is necessary to substitute this sand with other materials more abundant. The use of locally available materials is a very effective way to protect the environment, improve the physico-mechanical properties and durability of SCC and it can be a beneficial economical alternative. Few studies have addressed the effect of the binary and ternary combination of RS, CS and DS on the resistance to acid attacks of SCC.
Details
Keywords
Hebah Mohammad Aljabali, Rami H. Haddad and Laith H. Gharaibeh
The durability of concrete beams (150 × 250 × 1,600 mm3) strengthened using creative profiles with near-surface mounted (NSM) CFRP ropes under severe sulfate cyclic conditions was…
Abstract
Purpose
The durability of concrete beams (150 × 250 × 1,600 mm3) strengthened using creative profiles with near-surface mounted (NSM) CFRP ropes under severe sulfate cyclic conditions was experimentally investigated.
Design/methodology/approach
Parabolic and straight profiles of NSM-CFRP ropes were implemented without and with internal vertical and lateral dowelings using the CFRP ropes. Another group of concrete beams was repaired using similar schemes after being exposed to sulfate damage. The mechanical response of virgin (control), and sulfate damaged beams as well as of those retrofitted before and after exposure to sulfates, was evaluated under a four-point loading setup.
Findings
Mechanical evaluation of concrete indicated an increase in concrete’s brittleness and a decrease in its compressive strength by 21%. The beams strengthened using proposed configurations before being exposed to severe sulfate attack showed reductions in load capacity, displacement ductility and toughness of up to 24, 22 and 53%, respectively, yet an increase in stiffness of up to 16% compared to counterpart virgin-strengthened beams. The implantation of vertical and lateral dowels helped maintain the load capacity and improve the stiffness and displacement ductility for former beams by as much as 35 and 16%, respectively. In contrast, beams exposed to the same stage of sulfate treatment and then repaired with a parabolic profile (with and without vertical dowels) attained or surpassed the mechanical performance of relevantly strengthened and then sulfate-treated ones. The adopted retrofitting configurations did not alter the ductile flexural failure mode observed for virgin and sulfate-damaged beams.
Research limitations/implications
Concrete beams were strengthened and then subjected to sulfate attack in the absence of actual loading, which is not the case in the field.
Practical implications
Encouraging the use of the proposed repair configuration with CFRP ropes for concrete elements subjected to severe sulfate attack.
Social implications
The repair proposed may help maintain the integrity of marine structures for a long time to save on municipal spending on repair issues.
Originality/value
Limited work (if none) on the evaluation of repair durability of concrete flexural elements under sulfate severe condition was reported.
Details
Keywords
Prathamesh Pawar, Sudhir Patil and Sandeep Sathe
This study investigated the potential of partially replacing cement with red mud (RM) in concrete and examined its effects on its mechanical properties and microstructure. This…
Abstract
Purpose
This study investigated the potential of partially replacing cement with red mud (RM) in concrete and examined its effects on its mechanical properties and microstructure. This study aims to explore sustainable alternatives to traditional cement and evaluate the performance of concrete mixtures with varying percentages (%) of RM as cement replacement.
Design/methodology/approach
This research aims to comprehensively understand the impact of RM on concrete, aiming for both environmental sustainability and improved construction materials. Subsequently, concrete mixtures were prepared with varying RM contents, ranging from 0% to 21% in increments of 3%, replacing cement. The workability of these mixtures was evaluated using the Slump Cone Test, whereas their mechanical properties (compressive strength, flexural strength and split tensile strength) were assessed through standardized tests. The durability was further investigated via water absorption, acid attack, rapid chloride permeability tests, open porosity test and Sorptivity test. To gain deeper insights into the internal structure of concrete, microstructure analysis was conducted using X-ray diffraction and scanning electron microscopy. Finally, the results were analyzed and quantified.
Findings
The finding demonstrates that substituting 12% of cement with RM not only boosts the mechanical characteristics of concrete but also mitigates waste disposal. The microstructural analysis identified a denser cement matrix and improved bonding between the cement paste and the aggregates, suggesting potential improvements in strength and durability.
Originality/value
These results suggest that RM can be efficiently used to produce sustainable concrete with potential applications in construction projects with environmental considerations.
Details
Keywords
Suehail Aijaz Shah, Manzoor Ahmad Tantray and Jan Mohammad Banday
Durability of concrete can be enhanced by reducing the pore size/volume of pores or by entrapping the pores. This can be achieved by adding concrete admixtures that have particle…
Abstract
Purpose
Durability of concrete can be enhanced by reducing the pore size/volume of pores or by entrapping the pores. This can be achieved by adding concrete admixtures that have particle size finer than cement. In this study, GNP, having particle size much smaller than cement, has been introduced/added to concrete mix to control the pore size in concrete to tape out the contribution of GNP in the durability enhancement of concrete.
Design/methodology/approach
Different concrete mixes, at various water–cement ratios and amounts of graphene, have been manufactured to produce concrete containing three different %ages of GNP, i.e. 0%, 0.05% and 0.1%. To demonstrate the effect on durability of the concrete through the addition of GNP, these concrete samples have been subjected to repeated Freeze-Thaw cycles. Followed by testing after 28 days of curing, including weight loss, water absorption and strength, which are directly related to the durability aspect of concrete.
Findings
It has been observed that the addition of GNP to concrete mixes reduces the weight loss and pore size distribution and enhances tensile and compressive strength of concrete, thereby increasing the durability of concrete in unfavorable circumstances like freeze-thaw i.e. alternate hot and cold weather conditions.
Originality/value
This investigation presents original piece of experimental work conducted on modified concrete (GNP-based concrete). The aim is to construct the civil infrastructure in deep-cold region with increased life span and better performance.
Details
Keywords
Kumaran Coopamootoo and Reshma Rughooputh
The cementitious/chemical properties of the untreated CFA are dependent on the coal composition and previous burning conditions. The purpose of this paper is to investigate…
Abstract
Purpose
The cementitious/chemical properties of the untreated CFA are dependent on the coal composition and previous burning conditions. The purpose of this paper is to investigate whether untreated CFA can efficiently reduce cement replacement and does not require further combustion treatment to be a viable cement replacement.
Design/methodology/approach
Two types of mixes: Type I concrete and PCFA (Type I and 30 per cent untreated CFA) concrete were batched and subjected to compressive strength tests and cyclic exposures of 5 per cent sodium sulphate (Na2SO4) and 5 per cent magnesium sulphate (MgSO4), respectively.
Findings
PCFA mix was 41.1 and 35.21 per cent lower in strength compared to Type I at 28 and 56 days correspondingly. Continuous-sulphate-exposure resulted in slow but continued strength development for both mixes. However, the strengths of PCFA cubes exposed to cyclic sulphate and sulphate/magnesium salts continued to increase at a lower rate from their corresponding 28-day strength (rate of 18.7 per cent and strength 27.30 MPa in Na2SO4 and rate of 10.0 per cent and strength 25.30 MPa in MgSO4) while Type I specimens subjected to the same exposure conditions experienced drastic reductions in strength (rate of −15.0 per cent and strength 33.21 MPa in Na2SO4 and rate of −23.4 per cent and strength 29.94 MPa in MgSO4).
Research limitations/implications
Results justify the need for additional tests essentially: at different percentage replacement of untreated CFA, fineness of materials, chloride environment and longer exposures, to address the cementitious properties of untreated CFA as cement replacement.
Originality/value
Treatment methods for fly ashes require undoubtedly additional resources, energy input and cost. This paper paves the way to define whether untreated CFA can be used as cement replacement in concrete.