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Zeitschriftendaten
Format
Zeitschrift
eISSN
1338-3973
ISSN
1210-3896
Erstveröffentlichung
23 May 2011
Erscheinungsweise
4 Hefte pro Jahr
Sprachen
Englisch

Suche

Volumen 27 (2019): Heft 2 (June 2019)

Zeitschriftendaten
Format
Zeitschrift
eISSN
1338-3973
ISSN
1210-3896
Erstveröffentlichung
23 May 2011
Erscheinungsweise
4 Hefte pro Jahr
Sprachen
Englisch

Suche

7 Artikel
Uneingeschränkter Zugang

Comparative Study of Self-Compacting Concrete Containing Lightweight and Normal Aggregates

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 1 - 8

Zusammenfassung

Abstract

Based on the available literature, a simple method was adopted to calculate the packing density of aggregates and thereby reduce their void content by optimising their packing aggregates and by using two different sizes of coarse aggregates and fine aggregates. This study provides an understanding of the way in which the shape of aggregates affects the properties of self-compacting concrete (SCC). The fresh, hardened, and durable properties of SCC with normal and lightweight fly ash coarse aggregates are found at the corresponding age of the curing. Their values were compared with respect to SCC containing normal aggregates. A mix with fly ash aggregates was found to have better fresh concrete properties due to the round shape of the aggregates. After the packing of the aggregates, this mix was found to have better mechanical and durability properties than all the other concrete mixes.

Schlüsselwörter

  • Lightweight fly ash coarse aggregates
  • optimisation
  • Packing density
Uneingeschränkter Zugang

The Use of Polyethylene Terephthalate Waste for Modifying Asphalt Concrete Using the Marshall Test

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 9 - 15

Zusammenfassung

Abstract

This study considers the use of polyethylene terephthalate (PET) waste for modifying asphalt concrete. In the study, the optimum bitumen content of asphalt concrete was replaced with 4%, 6%, 8%, 10%, 12%, 14% and 16% of PET waste; the Marshall test was conducted on the samples. A comparison of the unmodified and PET-modified asphalt concrete showed that the stability of the modified asphalt concrete was reduced. The maximum stability for the PET waste-modified asphalt concrete was recorded at a content of 12% PET waste. This gives about a 20.4% reduction in stability. The study reveals that the addition of PET waste to the asphalt concrete causes a reduction in the flow value except with the addition of 14% and 16 % waste. This implies that the introduction of PET waste could improve the permanent deformation resistance of asphalt, although there is concern about a reduction in fatigue resistance.

Schlüsselwörter

  • Asphaltconcrete
  • Waste
  • Polyethylene terephthalate
  • Marshall test
  • Stability
  • flow
Uneingeschränkter Zugang

Alternative Micro-Milled Binders in Cold Recycling Technologies

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 16 - 20

Zusammenfassung

Abstract

In addition to bituminous binders (bituminous emulsion, foamed bitumen), hydraulic binders are applied in cold recycling technologies to increase the strength of a final structural layer as well as to increase its resistance to water and frost impacts. This paper deals with the use of energy by-products from fluidized bed coal combustion and mineral waste and their modification into reactive material with the potential of replacing commonly used hydraulic binders. The increase in the reactive potential takes place through a high-speed milling process where the mechanical-chemical activation of the material takes place. This process is associated with the refinement of the material, a higher proportion of micro and nanoparticles, an increased surface area, opening of particles, etc. The material treated exhibits binding properties, and it can be used as an active filler that allows for the partial or complete substitution of hydraulic binders. The experimental part is focused on the application of alternative binders to cold recycling mixtures and their assessment according to valid technical regulations, i.e., an assessment of their indirect tensile strength and water susceptibility as well as compressive strength and resistance to the effects of water and frost.

Schlüsselwörter

  • Cold recycling technologies
  • Hydraulic binders
  • Micro-milling
  • Indirect tensile strength
  • Resistance to water
Uneingeschränkter Zugang

The Use of Effective Coagulants and Flocculants to Intensify the Process of Water Purification at Coke Plants

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 21 - 28

Zusammenfassung

Abstract

The paper proposes a reagent method of water purification at the Kharkiv Coke Plant when using the phenolic wastewater in the water-circulating system, which corresponds to industry standards, together with coagulant (aluminum sulfate, aluminum hydroxychloride Pro-AQUA-18) and flocculant treatment (Extraflock and Besfloc). The use of cationic flocculants in water treatment has shown a high degree of efficiency in the removal of suspended substances compared with the Pro-AQUA-18 coagulant at a dose of 50 mg/dm3 or flocculant – 2-4 mg/dm3; it does not lead to the secondary pollution of the water and does not increase its corrosive activity. The purification of the clarified water was carried out using a filtration unit with a filtering load from a layer of quartz sand. The use of the proposed reagent method of water purification will allow it to be used for the technical purposes of the enterprise, reduce the consumption of fresh water, and eliminate the discharge of phenolic wastewater into the municipal sewer network.

Schlüsselwörter

  • Reagenttreatment
  • Coagulant
  • Flocculant
  • Circulating water supply
  • Coke plant
Uneingeschränkter Zugang

Study of the Mechanical Behaviour of a Clayey Soil Under Normal and Frozen Conditions

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 29 - 35

Zusammenfassung

Abstract

Lime and cement are quite compatible for stabilizing clayey soils; changes in a thermal regime may inversely affect the advantages of stabilized soil. The present study interprets changes in the mechanical behaviour of frozen and unfrozen Himalayan soil samples through an unconfined compressive strength test. The soil was treated with ground eggshell powder (3%-9%) and alkali activator (Sodium chloride) (2%-6%); it was reinforced with arbitrarily distributed polypropylene fibers (0.05%-0.15%). Standard 7, 14 and 21-day-old soil specimens were tested in unfrozen conditions, while fresh 21-day-old soil specimens were tested after 3, 5 and 10 freeze-thaw cycles. The design of the experiments was based on the Taguchi technique and arranged in an orthogonal array. The results of the research clearly show that poultry waste (eggshell powder) and alkaline soil stabilizer improved the strength behaviour of the subject soil. On the other hand, the polypropylene fibers played an important role in changing the brittle behaviour of the stabilized soil to ductile behaviour. The sudden collapse of a structure may be avoided by using polypropylene fibers.

Schlüsselwörter

  • Eggshellpowder
  • Sodium chloride
  • Polypropylene fiber
  • Freeze-thaw
  • Mechanical properties
  • Taguchi technique
Uneingeschränkter Zugang

Analyses of Monthly Discharges in Slovakia Using Hydrological Exploratory Methods and Statistical Methods

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 36 - 43

Zusammenfassung

Abstract

Detailed analyses of hydrological data are necessary in order to examine changes in their character. This article focuses on an analysis of the average monthly discharges of 14 stage-discharge gauging stations in Slovakia. The measured period is from 1931 to 2016. The approaches used are hydrological exploration methods, which were created by hydrologists to describe the behaviour of hydrological time series. The methods are used to identify a change-point through an analysis of any residuals, Pettitt´s test, and an analysis of the relationship between the mean annual discharge deviations from the long-term annual discharge and the deviations of the average monthly discharge from the long-term average monthly discharge. A considerable number of change-points were identified in the 1970s and 1980s. The results of the analyses show changes in the hydrological regimes, but to confirm the accuracy of the outcomes, it is also necessary to examine other hydrological and meteorological elements such as, e.g., precipitation and the air temperature.

Schlüsselwörter

  • Monthlydischarge
  • Hydrological exploratory methods
  • Change-point
Uneingeschränkter Zugang

Deterministic and Probabilistic Approaches in the Analysis of the Bearing Capacity of a Bridge Foundation on Undrained Clay Soil

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 44 - 51

Zusammenfassung

Abstract

This study aims at evaluating deterministic and probabilistic approaches for an analysis of the bearing capacity of a highway bridge foundation on undrained clay soil. The analysis of a rectangular concrete footing was presented for the ultimate strength limit state of the bearing resistance according to the formulation in ES EN 1991:2015 and ERA-Bridge Design Manual, which are the Ethiopian design codes for foundation structures. In the deterministic analysis, the traditional total safety factor method recommended by the ES EN 1991:2015, ERA and AASHTO LRFD method was implemented. It was assumed that design variables such as the soil parameters and loads would follow normal and lognormal distribution functions. With regard to the probabilistic methods, NESSUS-9.8 software, a statistical computer program, was used for the analysis. Comparisons were made between the results obtained from the traditional deterministic method and the reliability-based design approach. The evaluation asserts that the probabilistic approach is a better tool than the deterministic one for assessing the safety and reliability of geotechnical structures. The probabilistic design method rationally accounts for uncertainties more than the conventional deterministic method does. Thus, the author recommends that the National Design Codes of Ethiopia need to be revised and calibrated based on a reliability design format.

Schlüsselwörter

  • Deterministic
  • Probabilistic
  • Reliability
  • Bearing capacity
  • Bridge foundation
  • Undrained clay soil
7 Artikel
Uneingeschränkter Zugang

Comparative Study of Self-Compacting Concrete Containing Lightweight and Normal Aggregates

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 1 - 8

Zusammenfassung

Abstract

Based on the available literature, a simple method was adopted to calculate the packing density of aggregates and thereby reduce their void content by optimising their packing aggregates and by using two different sizes of coarse aggregates and fine aggregates. This study provides an understanding of the way in which the shape of aggregates affects the properties of self-compacting concrete (SCC). The fresh, hardened, and durable properties of SCC with normal and lightweight fly ash coarse aggregates are found at the corresponding age of the curing. Their values were compared with respect to SCC containing normal aggregates. A mix with fly ash aggregates was found to have better fresh concrete properties due to the round shape of the aggregates. After the packing of the aggregates, this mix was found to have better mechanical and durability properties than all the other concrete mixes.

Schlüsselwörter

  • Lightweight fly ash coarse aggregates
  • optimisation
  • Packing density
Uneingeschränkter Zugang

The Use of Polyethylene Terephthalate Waste for Modifying Asphalt Concrete Using the Marshall Test

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 9 - 15

Zusammenfassung

Abstract

This study considers the use of polyethylene terephthalate (PET) waste for modifying asphalt concrete. In the study, the optimum bitumen content of asphalt concrete was replaced with 4%, 6%, 8%, 10%, 12%, 14% and 16% of PET waste; the Marshall test was conducted on the samples. A comparison of the unmodified and PET-modified asphalt concrete showed that the stability of the modified asphalt concrete was reduced. The maximum stability for the PET waste-modified asphalt concrete was recorded at a content of 12% PET waste. This gives about a 20.4% reduction in stability. The study reveals that the addition of PET waste to the asphalt concrete causes a reduction in the flow value except with the addition of 14% and 16 % waste. This implies that the introduction of PET waste could improve the permanent deformation resistance of asphalt, although there is concern about a reduction in fatigue resistance.

Schlüsselwörter

  • Asphaltconcrete
  • Waste
  • Polyethylene terephthalate
  • Marshall test
  • Stability
  • flow
Uneingeschränkter Zugang

Alternative Micro-Milled Binders in Cold Recycling Technologies

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 16 - 20

Zusammenfassung

Abstract

In addition to bituminous binders (bituminous emulsion, foamed bitumen), hydraulic binders are applied in cold recycling technologies to increase the strength of a final structural layer as well as to increase its resistance to water and frost impacts. This paper deals with the use of energy by-products from fluidized bed coal combustion and mineral waste and their modification into reactive material with the potential of replacing commonly used hydraulic binders. The increase in the reactive potential takes place through a high-speed milling process where the mechanical-chemical activation of the material takes place. This process is associated with the refinement of the material, a higher proportion of micro and nanoparticles, an increased surface area, opening of particles, etc. The material treated exhibits binding properties, and it can be used as an active filler that allows for the partial or complete substitution of hydraulic binders. The experimental part is focused on the application of alternative binders to cold recycling mixtures and their assessment according to valid technical regulations, i.e., an assessment of their indirect tensile strength and water susceptibility as well as compressive strength and resistance to the effects of water and frost.

Schlüsselwörter

  • Cold recycling technologies
  • Hydraulic binders
  • Micro-milling
  • Indirect tensile strength
  • Resistance to water
Uneingeschränkter Zugang

The Use of Effective Coagulants and Flocculants to Intensify the Process of Water Purification at Coke Plants

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 21 - 28

Zusammenfassung

Abstract

The paper proposes a reagent method of water purification at the Kharkiv Coke Plant when using the phenolic wastewater in the water-circulating system, which corresponds to industry standards, together with coagulant (aluminum sulfate, aluminum hydroxychloride Pro-AQUA-18) and flocculant treatment (Extraflock and Besfloc). The use of cationic flocculants in water treatment has shown a high degree of efficiency in the removal of suspended substances compared with the Pro-AQUA-18 coagulant at a dose of 50 mg/dm3 or flocculant – 2-4 mg/dm3; it does not lead to the secondary pollution of the water and does not increase its corrosive activity. The purification of the clarified water was carried out using a filtration unit with a filtering load from a layer of quartz sand. The use of the proposed reagent method of water purification will allow it to be used for the technical purposes of the enterprise, reduce the consumption of fresh water, and eliminate the discharge of phenolic wastewater into the municipal sewer network.

Schlüsselwörter

  • Reagenttreatment
  • Coagulant
  • Flocculant
  • Circulating water supply
  • Coke plant
Uneingeschränkter Zugang

Study of the Mechanical Behaviour of a Clayey Soil Under Normal and Frozen Conditions

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 29 - 35

Zusammenfassung

Abstract

Lime and cement are quite compatible for stabilizing clayey soils; changes in a thermal regime may inversely affect the advantages of stabilized soil. The present study interprets changes in the mechanical behaviour of frozen and unfrozen Himalayan soil samples through an unconfined compressive strength test. The soil was treated with ground eggshell powder (3%-9%) and alkali activator (Sodium chloride) (2%-6%); it was reinforced with arbitrarily distributed polypropylene fibers (0.05%-0.15%). Standard 7, 14 and 21-day-old soil specimens were tested in unfrozen conditions, while fresh 21-day-old soil specimens were tested after 3, 5 and 10 freeze-thaw cycles. The design of the experiments was based on the Taguchi technique and arranged in an orthogonal array. The results of the research clearly show that poultry waste (eggshell powder) and alkaline soil stabilizer improved the strength behaviour of the subject soil. On the other hand, the polypropylene fibers played an important role in changing the brittle behaviour of the stabilized soil to ductile behaviour. The sudden collapse of a structure may be avoided by using polypropylene fibers.

Schlüsselwörter

  • Eggshellpowder
  • Sodium chloride
  • Polypropylene fiber
  • Freeze-thaw
  • Mechanical properties
  • Taguchi technique
Uneingeschränkter Zugang

Analyses of Monthly Discharges in Slovakia Using Hydrological Exploratory Methods and Statistical Methods

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 36 - 43

Zusammenfassung

Abstract

Detailed analyses of hydrological data are necessary in order to examine changes in their character. This article focuses on an analysis of the average monthly discharges of 14 stage-discharge gauging stations in Slovakia. The measured period is from 1931 to 2016. The approaches used are hydrological exploration methods, which were created by hydrologists to describe the behaviour of hydrological time series. The methods are used to identify a change-point through an analysis of any residuals, Pettitt´s test, and an analysis of the relationship between the mean annual discharge deviations from the long-term annual discharge and the deviations of the average monthly discharge from the long-term average monthly discharge. A considerable number of change-points were identified in the 1970s and 1980s. The results of the analyses show changes in the hydrological regimes, but to confirm the accuracy of the outcomes, it is also necessary to examine other hydrological and meteorological elements such as, e.g., precipitation and the air temperature.

Schlüsselwörter

  • Monthlydischarge
  • Hydrological exploratory methods
  • Change-point
Uneingeschränkter Zugang

Deterministic and Probabilistic Approaches in the Analysis of the Bearing Capacity of a Bridge Foundation on Undrained Clay Soil

Online veröffentlicht: 02 Jul 2019
Seitenbereich: 44 - 51

Zusammenfassung

Abstract

This study aims at evaluating deterministic and probabilistic approaches for an analysis of the bearing capacity of a highway bridge foundation on undrained clay soil. The analysis of a rectangular concrete footing was presented for the ultimate strength limit state of the bearing resistance according to the formulation in ES EN 1991:2015 and ERA-Bridge Design Manual, which are the Ethiopian design codes for foundation structures. In the deterministic analysis, the traditional total safety factor method recommended by the ES EN 1991:2015, ERA and AASHTO LRFD method was implemented. It was assumed that design variables such as the soil parameters and loads would follow normal and lognormal distribution functions. With regard to the probabilistic methods, NESSUS-9.8 software, a statistical computer program, was used for the analysis. Comparisons were made between the results obtained from the traditional deterministic method and the reliability-based design approach. The evaluation asserts that the probabilistic approach is a better tool than the deterministic one for assessing the safety and reliability of geotechnical structures. The probabilistic design method rationally accounts for uncertainties more than the conventional deterministic method does. Thus, the author recommends that the National Design Codes of Ethiopia need to be revised and calibrated based on a reliability design format.

Schlüsselwörter

  • Deterministic
  • Probabilistic
  • Reliability
  • Bearing capacity
  • Bridge foundation
  • Undrained clay soil

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