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1 – 10 of over 1000The feasibility is examined of devising a scheme for operating a joint keyword system in a given subject area using several independently compiled thesauri. It is suggested that…
Abstract
The feasibility is examined of devising a scheme for operating a joint keyword system in a given subject area using several independently compiled thesauri. It is suggested that if the individual keywords of each participating thesaurus represent identifiable concepts, and these concepts are given unique code numbers, then the code numbers enable the keywords of any participating thesaurus to be converted into the appropriate keywords of any other participant. Incompatibilities between keyword systems arise from differences in the selection and form of keywords. Eleven types of incompatibility are identified and a method of reconciliation is proposed for each. The types of incompatibility that can arise in a single language include those that arise between one language and another, so that a multilingual joint system presents no additional problems.
Andrea Nana Ofori-Boadu, DeAndria Bryant, Christian Bock-Hyeng, Zerihun Assefa, Frederick Aryeetey, Samira Munkaila and Elham Fini
The purpose of this study is to explore the feasibility of utilizing agricultural (almond shell, rice husk and wood) waste biochars for partial cement replacement by evaluating…
Abstract
Purpose
The purpose of this study is to explore the feasibility of utilizing agricultural (almond shell, rice husk and wood) waste biochars for partial cement replacement by evaluating the relationships between the physiochemical properties of biochars and the early-age characteristics of cement pastes.
Design/methodology/approach
Biochars are prepared through the thermal decomposition of biomass in an inert atmosphere. Using varying percentages, biochars are used to replace ordinary Portland cement (OPC) in cement pastes at a water/binder ratio of 0.35. Characterization methods include XPS, FTIR, SEM, TGA, BET, Raman, loss-on-ignition, setting, compression and water absorption tests.
Findings
Accelerated setting in biochar-modified cement pastes is attributed to chemical interactions between surface functional groups of biochars and calcium cations from OPC, leading to the early development of metal carboxylate and alkyne salts, alongside the typical calcium-silicate-hydrate (C-S-H). Also, metal chlorides such as calcium chlorides in biochars contribute to the accelerate setting in pastes. Lower compression strength and higher water absorption result from weakened microstructure due to poor C-S-H development as the high carbon content in biochars reduces water available for optimum C-S-H hydration. Amorphous silica contributes to strength development in pastes through pozzolanic interactions. With its optimal physiochemical properties, rice-husk biochars are best suited for cement replacement.
Research limitations/implications
While biochar parent material properties have an impact on biochar properties, these are not investigated in this study. Additional investigations will be conducted in the future.
Practical implications
Carbon/silicon ratio, oxygen/carbon ratio, alkali and alkaline metal content, chlorine content, carboxylic and alkyne surface functional groups and surface areas of biochars may be used to estimate biochar suitability for cement replacement. Biochars with chlorides and reactive functional groups such as C=C and COOH demonstrate potential for concrete accelerator applications. Such applications will speed up the construction of concrete structures and reduce overall construction time and related costs.
Social implications
Reductions in OPC production and agricultural waste deterioration will slow down the progression of negative environmental and human health impacts. Also, agricultural, manufacturing and construction employment opportunities will improve the quality of life in agricultural communities.
Originality/value
Empirical findings advance research and practice toward optimum utilization of biomass in cement-based materials.
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Faeze Nejati, Samira Ahmadi and S.A. Edalatpanah
Modern construction methods have been developed with the goal of reducing construction time as much as possible, which results in some situations during construction and within…
Abstract
Purpose
Modern construction methods have been developed with the goal of reducing construction time as much as possible, which results in some situations during construction and within the first few days after it, when concrete is subjected to exceptionally high loads. The precast concrete, which is the concrete in very early ages, may result in severe cracks or damages. In conventional construction projects, sometimes working with concrete, which had not reached its ultimate strength, is an unavoidable matter of fact. This paper aims to discuss these issues.
Design/methodology/approach
Researchers in the field of construction materials have done their best to make some changes in the different parts of the concrete in order to bring about reforms, based on the existing needs, and achieve new quality and primacy from concrete. One kind of concrete, the emergence of which dates back to many years ago, is self-compacting concrete. Thanks to its high efficiency for the parts with complex forms of high-density steel, this kind of concrete suggests new prospects.
Findings
This study aims at evaluating the effect of early loads on the 28-day compressive strength of concretes with zeolite and limestone powder under different curing conditions (wet or dry). In this regard, two self-compacting concrete mix designs with the same ratio of water to cementations materials and 0.4 percent and 10 percent zeolite have been considered; therefore, concrete cube samples with zeolite and limestone powder in different curing conditions at ages of three, one and seven days under preloading with 80–90 percent of compressive strength are damaged, and after curing in different conditions, their 28-day compressive strength is measured. According to the results, the recovery of the 28-day compressive strength of damaged samples, compared to that of intact samples, is possible in all curing conditions. The experiments that have been performed on concrete samples under dry and wet curing conditions show that the full recovery of compressive strength of damaged samples compared to that of intact ones happened only in preloaded samples at the age of one days, and in other ages (three and seven days) the 28-day strength reduction has occurred in damaged samples compared to the that in intact samples. The results of concrete samples with zeolite and without limestone powder at the age of one day indicate the greatest impact on other samples on the 28-day compressive strength of damaged samples compared to that of intact ones, occurring under dry condition.
Originality/value
This research analyzed and studied the influence under wet and dry curing conditions and the presence of limestone powder and zeolite fillers in recovering of the 28-day compressive strength of preloaded concrete samples at early stages (one, three and seven days) after the construction of the concrete.
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Feng Chen, Zhongjin Wang, Dong Zhang and Shuai Zeng
Explore the development trend of chemically-improved soil in railway engineering.
Abstract
Purpose
Explore the development trend of chemically-improved soil in railway engineering.
Design/methodology/approach
In this paper, the technical standards home and abroad were analyzed. Laboratory test, field test and monitoring were carried out.
Findings
The performance design system of the chemically-improved soil should be established.
Originality/value
On the basis of the performance design, the test methods and standards for various properties of chemically-improved soil should be established to evaluate the improvement effect and control the engineering quality.
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Hassan A.M. Mhamoud and Jia Yanmin
This study aims to focus on the resistance to elevated temperatures of up to 700ºC of high-performance concrete (HPC) compared to ordinary Portland concrete (OPC) with regards to…
Abstract
Purpose
This study aims to focus on the resistance to elevated temperatures of up to 700ºC of high-performance concrete (HPC) compared to ordinary Portland concrete (OPC) with regards to mass loss and residual compressive and flexural strength.
Design/methodology/approach
Two mixtures were developed to test. The first mixture, OPC, was used as the control, and the second mixture was HPC. After 28 days under water (per Chinese standard), the samples were tested for compressive strength and residual strength.
Findings
The test results showed that at elevated temperatures of up to 500ºC, each mixture experienced mass loss. Below this temperature, the strength and the mass loss did not differ greatly.
Originality/value
When adding a 10 per cent silica fume, 25 per cent fly, 25 per cent slag to HPC, the compressive strength increased by 17 per cent and enhanced the residual compressive strength. A sharp decrease was observed in the residual flexural strength of HPC when compared to OPC after exposure to temperatures of 700ºC.
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Hadji Ben Salah, Benamara Dalila and Taallah Bachir
This paper aims to express a mathematical model that predicts the effect of mineral additives on the physical–mechanical properties of high-performance sand concrete (HPSC), using…
Abstract
Purpose
This paper aims to express a mathematical model that predicts the effect of mineral additives on the physical–mechanical properties of high-performance sand concrete (HPSC), using SAS's JMP7 statistical analysis software.
Design/methodology/approach
A mixture design modeling approach is applied to sand concrete (SC) for optimizing mixtures without being obliged to do a lot of experiments, where the cement is partially replaced with two mineral additives silica fume (SF) and blast furnace slag (BFS) in proportions as high as 20% of the mass. A total of 15 mixtures of sand concrete is prepared in the laboratory using this analytical technique in combinations with binary and ternary systems to estimate the workability and the compressive strength (CS) of sand concrete at 7 and 28 days.
Findings
The results obtained showed that the use of derived models based on the experimental design approach greatly assisted in understanding the interactions between the various parameters of the studied mixtures; the mathematical models present excellent correlation coefficients (R² = 0.96 for CS7 days, R² = 0.93 for CS28 days and R² = 0.95 for slump) for all studied responses. Moreover, it was also found that the inclusion of additives (SF and BFS) in binary mixture SC12 and ternary mixtures SC8 leads to a significant improvement in mechanical strength compared to reference sand concrete SC15. These results give the possibility to obtain a formulation of HPSC.
Originality/value
This paper shows the possibility of manufacturing high-performance sand-concrete with good compressive strength; the developed mathematical model by using SAS's JMP7 statistical analysis software allowed us to reach a strength compression value of about 60 MPa, in 28 days, by replacing 10% of the cement weight with silica fume. Furthermore, with partial replacement of the cement weight (15%) with two additions such as silica fume (10%) and blast furnace slag (5%), a 58 MPa of compressive strength can be achieved, without overlooking the fact that this can be a key economic and environmental alternative.
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Hassan A.M. Mhamoud and Jia Yanmin
This study aims to investigate the effectiveness of different additives (individual effects) in improving the strength of concrete to resist temperatures of up to 60ºC.
Abstract
Purpose
This study aims to investigate the effectiveness of different additives (individual effects) in improving the strength of concrete to resist temperatures of up to 60ºC.
Design/methodology/approach
In all, 13 different mixtures with a constant water/binder ratio of 0.36 and grade M40 were prepared by using ordinary Portland concrete alone, or with partial replacement by fly ash (FA), blast-furnace slag, silica fume (SF) and a combination of all three. After 7 and 28 days under water, their strength and residual strength were measured.
Findings
The results of testing revealed that the addition of 10 per cent SF was found to result in the greatest increase in compressive strength and flexural strength along with decreased the residual strengths. The addition of FA increased the compressive strength and enhanced the residual compressive strength. However, it also decreased the residual flexural strength.
Originality/value
The addition of slag achieved better flexural strength and the best residual compressive strength. The combination of additives also enhanced the compressive strength but was not found to be better than using SF alone.
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Eric Asa, Ahmed Shaker Anna and Edmund Baffoe-Twum
This paper aims to discuss the evaluation of the compressive and splitting tensile strength of concrete mixes containing different proportions of up to 20 per cent glass…
Abstract
Purpose
This paper aims to discuss the evaluation of the compressive and splitting tensile strength of concrete mixes containing different proportions of up to 20 per cent glass aggregate. Portions of sand in concretes with and without admixtures were replaced with measurements of glass aggregates.
Design/methodology/approach
“Glascrete” is a term used for concrete in which crushed glass is used as a substitute for all or part of the aggregates. Glass can be recycled many times without changing its properties, making it an ideal material in concrete. Overall, 144 cubes and 144 cylinders of glascretes were prepared with different admixtures and subjected to compressive and splitting tensile strength test.
Findings
A comparison with a 21-day control mix indicated that glass aggregates are replacing sand in concrete ranging from 5 to 20 per cent by volume, resulting in 3.8-10.6 per cent and 3.9-16.4 per cent fall in compressive and tensile strength, respectively. However, the use of mineral admixture improved the properties of the mixes at 3, 7, 14 and 21 days.
Social implications
Cities worldwide are congested, and even those with the best waste-management system would have issues with waste disposal after the year 2030. Consequently, waste management is a current issue for cities all over the world.
Originality/value
This study aims to evaluate the physical properties of mortar mixes that contain different volumes of waste glass as substitutes for fine aggregate with or without additives. Mineral additives are used to improve the mechanical properties of glascrete mixes in addition to its chemical resistance by absorbing the OH− ions responsible for the possible alkali-silica reaction (ASR). It also reduces the adverse effects of mix-dimensional stability. Water-reducing admixtures are used to reduce the impact of the ASR by minimizing the amount of moisture in concrete, in effect decreasing the possible expansion of any produced gel. In this research, compressive and splitting tensile strength of concrete mortar containing waste glass of limited substitutions is evaluated.
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Chengqiang Ren, Yi He, Dezhi Zeng and Taihe Shi
The long‐term durability of cement becomes an important challenge in oil and gas wells due to the aggressive acid gas. H2S has been found in more and more wells. The purpose of…
Abstract
Purpose
The long‐term durability of cement becomes an important challenge in oil and gas wells due to the aggressive acid gas. H2S has been found in more and more wells. The purpose of this research was to add polymer latex to the Class G cement in order to promote the H2S corrosion resistance of oilwell cement.
Design/methodology/approach
The water loss and thickening time of cement slurry and compressive strength and gas permeability of bond cement were investigated to determine the cement formulation. The corrosion resistance of the polymer cement was compared to base Class G cement in solution with 1.8 MPa H2S at 120°C.
Findings
The optimum concentration of polystyrene latex was determined as 5 percent. The permeability change, compressive strength loss and corrosion ratio of latex cement were all lower than for the base Class G cement. The electrochemical impedance spectroscopy results and microstructure details confirmed that the latex cement had stronger resistance to the aggressive medium. Thus, latex cement had excellent corrosion resistance to H2S.
Originality/value
The findings of this study can further improve the sulfide resistance of Class G cement. Two roles of the polystyrene latex were observed in the cement, including interstitial in‐filling of the pore structure and packing around hydration products, which are proposed to properly explain the results.
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Md. Hazrat Ali, Gani Issayev, Essam Shehab and Shoaib Sarfraz
In recent years, 3D printing technologies have been widely used in the construction industry. 3D printing in construction is very attractive because of its capability of process…
Abstract
Purpose
In recent years, 3D printing technologies have been widely used in the construction industry. 3D printing in construction is very attractive because of its capability of process automation and the possibility of saving labor, waste materials, construction time and hazardous procedures for humans. Significant researches were conducted to identify the performance of the materials, while some researches focused on the development of novel techniques and methods, such as building information modeling. This paper aims to provide a detailed overview of the state-of-the-art of currently used 3D printing technologies in the construction areas and global acceptance in its applications.
Design/methodology/approach
The working principle of additive manufacturing in construction engineering (CE) is presented in terms of structural design, materials used and theoretical background of the leading technologies that are used to construct buildings and structures as well as their distinctive features.
Findings
The trends of 3D printing processes in CE are very promising, as well as the development of novel materials, will gain further momentum. The findings also indicate that the digital twin (DT) in construction technology would bring the industry a step forward toward achieving the goal of Industry 5.0.
Originality/value
This review highlights the prospects of digital manufacturing and the DT in construction engineering. It also indicates the future research direction of 3D printing in various constriction sectors.
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