Gokhan Baykal - Academia.edu (original) (raw)
Papers by Gokhan Baykal
Transportation Research Record, Nov 21, 2021
Soils with high plasticity and high swell potential undergo great volume changes in the presence ... more Soils with high plasticity and high swell potential undergo great volume changes in the presence of unstable water content changes. The resulting expansion leads to damage to pavements and/or lightweight structures with such a subsoil. Expansive soils can be improved by adding chemical stabilizers such as lime, fly ash and micro cement. To construct a highway on an expansive subgrade soil, the subgrade should be stabilized to satisfy the minimum requirements of the highway standards. In this research, expansive clay samples were collected from clay deposits in the Akyurt district of Ankara (Turkey), near Esenboğa Airport. The swelling, strength and resilient modulus properties of the soil samples were determined via laboratory tests. First, reference tests were carried out on natural soil samples. Then, the clay samples were mixed with lime agent at different percentages (1%, 3%, 5%, 7% and 9%) according to the dry weight of the soil. The index, swelling, strength and resilient modulus (Mr) properties of these samples were determined. The soil samples were tested at 7, 28, 56 and 90-day curing times for each percentage of lime agent considered. The changes in the abovementioned properties, especially with regard to the effect of curing time on improvement, were interpreted in this research. Designing for a 7% lime content and a 28-day curing time can be a sound solution for addressing the expansive clay studied in this research, since the criteria of the Turkish Highway Standards are satisfied under these conditions.
Transportation Research Record, Nov 21, 2021
Soils with high plasticity and high swell potential undergo great volume changes in the presence ... more Soils with high plasticity and high swell potential undergo great volume changes in the presence of unstable water content changes. The resulting expansion leads to damage to pavements and/or lightweight structures with such a subsoil. Expansive soils can be improved by adding chemical stabilizers such as lime, fly ash and micro cement. To construct a highway on an expansive subgrade soil, the subgrade should be stabilized to satisfy the minimum requirements of the highway standards. In this research, expansive clay samples were collected from clay deposits in the Akyurt district of Ankara (Turkey), near Esenboğa Airport. The swelling, strength and resilient modulus properties of the soil samples were determined via laboratory tests. First, reference tests were carried out on natural soil samples. Then, the clay samples were mixed with lime agent at different percentages (1%, 3%, 5%, 7% and 9%) according to the dry weight of the soil. The index, swelling, strength and resilient modulus (Mr) properties of these samples were determined. The soil samples were tested at 7, 28, 56 and 90-day curing times for each percentage of lime agent considered. The changes in the abovementioned properties, especially with regard to the effect of curing time on improvement, were interpreted in this research. Designing for a 7% lime content and a 28-day curing time can be a sound solution for addressing the expansive clay studied in this research, since the criteria of the Turkish Highway Standards are satisfied under these conditions.
Symposium GREEN'93-Geotechnics related to the environment, 1995
Symposium GREEN'93-Geotechnics related to the environment, 1995
Environmental Geotechnology. Balkema, 1992
MRS Proceedings, 1987
Compacted fly ash, lime, bentonite and water mixtures were cured at 230 and 50 0 C, for 1, 28, 90... more Compacted fly ash, lime, bentonite and water mixtures were cured at 230 and 50 0 C, for 1, 28, 90 and 180 days. Cementitious products and microstructure were observed by scanning electron microscopy, energy dispersive x-ray spectrometry and x-ray diffractometry. Unconfined compressive strength changes are correlated to the formation of new mineral phases. For bentonite-limefly ash mixtures, strength increased from 1050 kPa (I day) to 2,300 kPa (90 days) and then slightly increased to 2,400 kPa after 180 days at-23 0 C. Ettringite is the most abundant mineral associated with the increased compressive strength. New minerals identified in the 23 0 C mixtures include calcium silicate hydrate-Type 1, afwillite and ettringite. Acicular crystals of these and other minerals were formed by the hydration of lime and fly ash in the montmorillonitic clay. The cementitious phases create a rigid framework joining spheres and clay aggregates. Continued reaction dissolves some of the spheres and slightly reduces the rigidity of the cured samples.
Insights and Innovations in Structural Engineering, Mechanics and Computation, 2016
Geosynthetics in Civil and Environmental Engineering
The pullout performance of a locally manufactured geogrid is investigated by laboratory pullout t... more The pullout performance of a locally manufactured geogrid is investigated by laboratory pullout test, performed with a modified large scale direct shear device which has been designed and constructed at Bogazici University, Due to the lack of a generally accepted standard method, all researchers have developed their own equipment. The differences in the testing procedures and equipment make the comparison of the test results difficult. But mainly the logic and effect of the various parameters on the pull out performance is the same in most of the papers presented so far. The test device presented here is a multi purpose large size direct shear device capable of conducting pull out tests. With 0.3 m×0.3m×0.3m sample box, the testing equipment is very practical. Uniaxial polypropylene geogrid and crushed rock was tested. The effects of displacement rate, confining pressure and specimen width on the pull out response have been investigated. The coefficient of interaction, which is required for the design of reinforced earth structures has been computed under different confining pressures. The results are interpreted and conclusions are presented. Comments for a better test setup are made.
"SP-153: Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete Proceedings Fifth International Conference Milwauk"
"SP-153: Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete Proceedings Fifth International Conference Milwauk"
Evsel Kati Atik (EKA) depolama sahalari, başlica evsel ve endüstriyel atiklarin bulunduğu heteroj... more Evsel Kati Atik (EKA) depolama sahalari, başlica evsel ve endüstriyel atiklarin bulunduğu heterojen karişimlarin depolandiği yerlerdir. EKA larin mukavemet ve sikişabilirlik gibi mekanik özellikleri, çöpün kompozisyonuna, depolanan malzemenin bileşenlerinin mekanik özelliklerine, su muhtevasina ve bozulmanin etkisine bağlidir. Sismik bölgelerdeki depolama sahalari sadece statik yükler altinda değil, ayni zamanda sismik şartlar altinda da göçmelere karşi güvenli olmalidir. Depolama sahalarinin dinamik analizinin güvenli olmasi için, atik malzemenin dinamik özelliklerinin doğru belirlenmesi çok önemlidir. Depolama sahalarinin deprem sirasindaki davranişi, nümerik modellerle analiz edilebileceği gibi, sarsma masasi deneyleri ile de belirlenebilmektedir. Bu çalişmada, EKA depolama sahasiinin deprem sirasindaki davranişinin sarsma masasi modelleri ile belirlenmesi amaçlanmaktadir. Çalişma üç aşamadan oluşmaktadir. İlk aşamada, sarsma masasi deneylerinde kullanilacak malzemenin fiziksel ö...
Geosynthetics International, 2006
Findings from recent research reveal that the ductility, toughness and resistance to tensile crac... more Findings from recent research reveal that the ductility, toughness and resistance to tensile cracking of clays can be improved with the inclusion of short fibers. Tire buffings derived from the tire retread process can be elongated in shape and may be utilised as fiber reinforcement elements. The objective of the present research is to study the compaction and shear strength behavior of clay with tire buffing inclusions. Mixtures of low-plasticity kaolinitic clay with 10% by dry weight of tire buffing inclusions were prepared at both standard and modified compaction energy. The drained and undrained responses of the clay and composite soils were evaluated using the direct shear test. It was found that the drained shear strength of the clay was essentially unchanged by the introduction of rubber buffings or by an increase in the level of compaction energy employed. Its undrained strength was also not changed when standard compaction energy was used, but decreased slightly, showing a ...
Granular Matter, 2009
The behavior of granular materials mainly depends on the mechanical and engineering properties of... more The behavior of granular materials mainly depends on the mechanical and engineering properties of particles in its structural matrix. Crushing or breakage of granular materials under compression or shear occurs when the energy available is sufficient to overcome the resistance of the material. Relatively little systematic research has been conducted regarding how to evaluate or quantify particle crushing and how it effects the engineering properties of the granular materials. The aim of this study is to investigate the effect of crushing on the bulk behavior of granular materials by using manufactured granular materials (MGM) rather than using a naturally occurring cohesionless granular material. MGM allow changing only one particle parameter, namely the "crushing strength". Four different categories of MGM (with different crushing strength) are used to study the effect on the bulk shear strength, stiffness modulus, friction and dilatancy angle "engineering properties". A substantial influence on the stress-strain behavior and engineering properties of granular materials is observed. Higher confining stress causes some non-uniformity (strong variations/jumps) in volumetric strain and a constant volumetric strain is not always observed under large shear
Energy and Buildings, 2011
In the autoclaved aerated concrete production, aluminum powder is used to create pores which lead... more In the autoclaved aerated concrete production, aluminum powder is used to create pores which lead to high thermal insulation property. In the present technique developed, snow or crushed ice is added to fly ash over optimum moisture content and compacted to obtain an increased porosity and a stronger matrix. The main objective of this study is to investigate the effect of various practical mix percentages of snow into fly ash and evaluation of their insulation properties. The optimum water content of fly ash was determined and additional snow with percentages of 10, 20 and 30 by weight are added to type C fly ash samples. Thermal conductivity tests were performed on samples to evaluate the insulation capability of the snow added fly ash samples where information is not readily available in the literature. The highest improvement in the thermal conductivity is obtained by adding 20 per cent snow to fly ash samples over optimum moisture content. Higher percentages of snow addition resulted in interconnected voids, causing lower thermal conductivity performance. These findings can be utilized for nonstructural insulating construction blocks and also as an insulation layer for embankments in permafrost areas.
The study reports the results of physical, mineralogical, and micromorphological tests on laborat... more The study reports the results of physical, mineralogical, and micromorphological tests on laboratory prepared mixtures of bentonite (75wt%), Class C fly ash (20wt%), and lime (5wt%). Combined results of X-ray powder diffraction, scanning electron microscopy, compressive strength tests, and elastic modulus calculations on the same test specimens after curing for periods of time up to 180 days at 23 deg C or 50 deg C provide much insight on the stabilization reaction mechanisms in a montmorillonite-rich material. Ettringite, C-S-H gel, and afwillite create a 3-dimensional network of bound particles that is responsible for increased compressive strengths and elastic moduli 15-17 times greater than the untreated bentonite. Test results produced after one day of curing at 50 deg C are comparable to those obtained after 28 days of curing at 23 deg C.
The morphological, mineralogical, and stress-strain properties of compacted bentonite-fly ash-lim... more The morphological, mineralogical, and stress-strain properties of compacted bentonite-fly ash-lime, bentonite-fly ash, and bentonite-lime cured at 23 deg C and 50 deg C were compared. The development of microstructure and cementitious crystals was observed by scanning electron microscopy, energy dispersive spectral analysis, and x-ray diffractometry. The elastic moduli and compressive strengths were obtained from unconsolidated, undrained triaxial and unconfined compression tests. Curing at 50 deg C increased the rate of strength development. Similar elastic moduli were obtained for specimens cured for one day at 50 deg C and 28 days at 23 deg C. However, strain at failure after one day of curing at 50 deg C was considerably higher than that obtained after 28 days of curing at 23 deg C. The samples cured at 50 deg C yielded higher compressive strengths relative to the samples cured at 23 deg C. Cementitious minerals formed at both curing temperatures were similar except that the cem...
Interface between construction materials and soils play an important role in many geotechnical sy... more Interface between construction materials and soils play an important role in many geotechnical systems, including retaining walls, shallow and deep foundations. Interface behavior is studied using split samples consisting of concrete block at the bottom half and soil at the top half of the direct shear. The objective of this research is to assess the effect of aggregate crushing at the concrete-soil interface. To be able to control the large number of parameters affecting the interface behavior, granular soil was manufactured using fly ash by cold-bonding pelletization technique with predetermined shape, size, grain size distribution, surface roughness, water absorption, unit weight and crushing strength. The physical and mechanical properties of these aggregates were investigated by using conventional soil mechanics tests. Interface tests between lightweight aggregates and concrete showed that the effects of grain crushing, particle shape and the surface roughness of aggregates pla...
Transportation Research Record, Nov 21, 2021
Soils with high plasticity and high swell potential undergo great volume changes in the presence ... more Soils with high plasticity and high swell potential undergo great volume changes in the presence of unstable water content changes. The resulting expansion leads to damage to pavements and/or lightweight structures with such a subsoil. Expansive soils can be improved by adding chemical stabilizers such as lime, fly ash and micro cement. To construct a highway on an expansive subgrade soil, the subgrade should be stabilized to satisfy the minimum requirements of the highway standards. In this research, expansive clay samples were collected from clay deposits in the Akyurt district of Ankara (Turkey), near Esenboğa Airport. The swelling, strength and resilient modulus properties of the soil samples were determined via laboratory tests. First, reference tests were carried out on natural soil samples. Then, the clay samples were mixed with lime agent at different percentages (1%, 3%, 5%, 7% and 9%) according to the dry weight of the soil. The index, swelling, strength and resilient modulus (Mr) properties of these samples were determined. The soil samples were tested at 7, 28, 56 and 90-day curing times for each percentage of lime agent considered. The changes in the abovementioned properties, especially with regard to the effect of curing time on improvement, were interpreted in this research. Designing for a 7% lime content and a 28-day curing time can be a sound solution for addressing the expansive clay studied in this research, since the criteria of the Turkish Highway Standards are satisfied under these conditions.
Transportation Research Record, Nov 21, 2021
Soils with high plasticity and high swell potential undergo great volume changes in the presence ... more Soils with high plasticity and high swell potential undergo great volume changes in the presence of unstable water content changes. The resulting expansion leads to damage to pavements and/or lightweight structures with such a subsoil. Expansive soils can be improved by adding chemical stabilizers such as lime, fly ash and micro cement. To construct a highway on an expansive subgrade soil, the subgrade should be stabilized to satisfy the minimum requirements of the highway standards. In this research, expansive clay samples were collected from clay deposits in the Akyurt district of Ankara (Turkey), near Esenboğa Airport. The swelling, strength and resilient modulus properties of the soil samples were determined via laboratory tests. First, reference tests were carried out on natural soil samples. Then, the clay samples were mixed with lime agent at different percentages (1%, 3%, 5%, 7% and 9%) according to the dry weight of the soil. The index, swelling, strength and resilient modulus (Mr) properties of these samples were determined. The soil samples were tested at 7, 28, 56 and 90-day curing times for each percentage of lime agent considered. The changes in the abovementioned properties, especially with regard to the effect of curing time on improvement, were interpreted in this research. Designing for a 7% lime content and a 28-day curing time can be a sound solution for addressing the expansive clay studied in this research, since the criteria of the Turkish Highway Standards are satisfied under these conditions.
Symposium GREEN'93-Geotechnics related to the environment, 1995
Symposium GREEN'93-Geotechnics related to the environment, 1995
Environmental Geotechnology. Balkema, 1992
MRS Proceedings, 1987
Compacted fly ash, lime, bentonite and water mixtures were cured at 230 and 50 0 C, for 1, 28, 90... more Compacted fly ash, lime, bentonite and water mixtures were cured at 230 and 50 0 C, for 1, 28, 90 and 180 days. Cementitious products and microstructure were observed by scanning electron microscopy, energy dispersive x-ray spectrometry and x-ray diffractometry. Unconfined compressive strength changes are correlated to the formation of new mineral phases. For bentonite-limefly ash mixtures, strength increased from 1050 kPa (I day) to 2,300 kPa (90 days) and then slightly increased to 2,400 kPa after 180 days at-23 0 C. Ettringite is the most abundant mineral associated with the increased compressive strength. New minerals identified in the 23 0 C mixtures include calcium silicate hydrate-Type 1, afwillite and ettringite. Acicular crystals of these and other minerals were formed by the hydration of lime and fly ash in the montmorillonitic clay. The cementitious phases create a rigid framework joining spheres and clay aggregates. Continued reaction dissolves some of the spheres and slightly reduces the rigidity of the cured samples.
Insights and Innovations in Structural Engineering, Mechanics and Computation, 2016
Geosynthetics in Civil and Environmental Engineering
The pullout performance of a locally manufactured geogrid is investigated by laboratory pullout t... more The pullout performance of a locally manufactured geogrid is investigated by laboratory pullout test, performed with a modified large scale direct shear device which has been designed and constructed at Bogazici University, Due to the lack of a generally accepted standard method, all researchers have developed their own equipment. The differences in the testing procedures and equipment make the comparison of the test results difficult. But mainly the logic and effect of the various parameters on the pull out performance is the same in most of the papers presented so far. The test device presented here is a multi purpose large size direct shear device capable of conducting pull out tests. With 0.3 m×0.3m×0.3m sample box, the testing equipment is very practical. Uniaxial polypropylene geogrid and crushed rock was tested. The effects of displacement rate, confining pressure and specimen width on the pull out response have been investigated. The coefficient of interaction, which is required for the design of reinforced earth structures has been computed under different confining pressures. The results are interpreted and conclusions are presented. Comments for a better test setup are made.
"SP-153: Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete Proceedings Fifth International Conference Milwauk"
"SP-153: Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete Proceedings Fifth International Conference Milwauk"
Evsel Kati Atik (EKA) depolama sahalari, başlica evsel ve endüstriyel atiklarin bulunduğu heteroj... more Evsel Kati Atik (EKA) depolama sahalari, başlica evsel ve endüstriyel atiklarin bulunduğu heterojen karişimlarin depolandiği yerlerdir. EKA larin mukavemet ve sikişabilirlik gibi mekanik özellikleri, çöpün kompozisyonuna, depolanan malzemenin bileşenlerinin mekanik özelliklerine, su muhtevasina ve bozulmanin etkisine bağlidir. Sismik bölgelerdeki depolama sahalari sadece statik yükler altinda değil, ayni zamanda sismik şartlar altinda da göçmelere karşi güvenli olmalidir. Depolama sahalarinin dinamik analizinin güvenli olmasi için, atik malzemenin dinamik özelliklerinin doğru belirlenmesi çok önemlidir. Depolama sahalarinin deprem sirasindaki davranişi, nümerik modellerle analiz edilebileceği gibi, sarsma masasi deneyleri ile de belirlenebilmektedir. Bu çalişmada, EKA depolama sahasiinin deprem sirasindaki davranişinin sarsma masasi modelleri ile belirlenmesi amaçlanmaktadir. Çalişma üç aşamadan oluşmaktadir. İlk aşamada, sarsma masasi deneylerinde kullanilacak malzemenin fiziksel ö...
Geosynthetics International, 2006
Findings from recent research reveal that the ductility, toughness and resistance to tensile crac... more Findings from recent research reveal that the ductility, toughness and resistance to tensile cracking of clays can be improved with the inclusion of short fibers. Tire buffings derived from the tire retread process can be elongated in shape and may be utilised as fiber reinforcement elements. The objective of the present research is to study the compaction and shear strength behavior of clay with tire buffing inclusions. Mixtures of low-plasticity kaolinitic clay with 10% by dry weight of tire buffing inclusions were prepared at both standard and modified compaction energy. The drained and undrained responses of the clay and composite soils were evaluated using the direct shear test. It was found that the drained shear strength of the clay was essentially unchanged by the introduction of rubber buffings or by an increase in the level of compaction energy employed. Its undrained strength was also not changed when standard compaction energy was used, but decreased slightly, showing a ...
Granular Matter, 2009
The behavior of granular materials mainly depends on the mechanical and engineering properties of... more The behavior of granular materials mainly depends on the mechanical and engineering properties of particles in its structural matrix. Crushing or breakage of granular materials under compression or shear occurs when the energy available is sufficient to overcome the resistance of the material. Relatively little systematic research has been conducted regarding how to evaluate or quantify particle crushing and how it effects the engineering properties of the granular materials. The aim of this study is to investigate the effect of crushing on the bulk behavior of granular materials by using manufactured granular materials (MGM) rather than using a naturally occurring cohesionless granular material. MGM allow changing only one particle parameter, namely the "crushing strength". Four different categories of MGM (with different crushing strength) are used to study the effect on the bulk shear strength, stiffness modulus, friction and dilatancy angle "engineering properties". A substantial influence on the stress-strain behavior and engineering properties of granular materials is observed. Higher confining stress causes some non-uniformity (strong variations/jumps) in volumetric strain and a constant volumetric strain is not always observed under large shear
Energy and Buildings, 2011
In the autoclaved aerated concrete production, aluminum powder is used to create pores which lead... more In the autoclaved aerated concrete production, aluminum powder is used to create pores which lead to high thermal insulation property. In the present technique developed, snow or crushed ice is added to fly ash over optimum moisture content and compacted to obtain an increased porosity and a stronger matrix. The main objective of this study is to investigate the effect of various practical mix percentages of snow into fly ash and evaluation of their insulation properties. The optimum water content of fly ash was determined and additional snow with percentages of 10, 20 and 30 by weight are added to type C fly ash samples. Thermal conductivity tests were performed on samples to evaluate the insulation capability of the snow added fly ash samples where information is not readily available in the literature. The highest improvement in the thermal conductivity is obtained by adding 20 per cent snow to fly ash samples over optimum moisture content. Higher percentages of snow addition resulted in interconnected voids, causing lower thermal conductivity performance. These findings can be utilized for nonstructural insulating construction blocks and also as an insulation layer for embankments in permafrost areas.
The study reports the results of physical, mineralogical, and micromorphological tests on laborat... more The study reports the results of physical, mineralogical, and micromorphological tests on laboratory prepared mixtures of bentonite (75wt%), Class C fly ash (20wt%), and lime (5wt%). Combined results of X-ray powder diffraction, scanning electron microscopy, compressive strength tests, and elastic modulus calculations on the same test specimens after curing for periods of time up to 180 days at 23 deg C or 50 deg C provide much insight on the stabilization reaction mechanisms in a montmorillonite-rich material. Ettringite, C-S-H gel, and afwillite create a 3-dimensional network of bound particles that is responsible for increased compressive strengths and elastic moduli 15-17 times greater than the untreated bentonite. Test results produced after one day of curing at 50 deg C are comparable to those obtained after 28 days of curing at 23 deg C.
The morphological, mineralogical, and stress-strain properties of compacted bentonite-fly ash-lim... more The morphological, mineralogical, and stress-strain properties of compacted bentonite-fly ash-lime, bentonite-fly ash, and bentonite-lime cured at 23 deg C and 50 deg C were compared. The development of microstructure and cementitious crystals was observed by scanning electron microscopy, energy dispersive spectral analysis, and x-ray diffractometry. The elastic moduli and compressive strengths were obtained from unconsolidated, undrained triaxial and unconfined compression tests. Curing at 50 deg C increased the rate of strength development. Similar elastic moduli were obtained for specimens cured for one day at 50 deg C and 28 days at 23 deg C. However, strain at failure after one day of curing at 50 deg C was considerably higher than that obtained after 28 days of curing at 23 deg C. The samples cured at 50 deg C yielded higher compressive strengths relative to the samples cured at 23 deg C. Cementitious minerals formed at both curing temperatures were similar except that the cem...
Interface between construction materials and soils play an important role in many geotechnical sy... more Interface between construction materials and soils play an important role in many geotechnical systems, including retaining walls, shallow and deep foundations. Interface behavior is studied using split samples consisting of concrete block at the bottom half and soil at the top half of the direct shear. The objective of this research is to assess the effect of aggregate crushing at the concrete-soil interface. To be able to control the large number of parameters affecting the interface behavior, granular soil was manufactured using fly ash by cold-bonding pelletization technique with predetermined shape, size, grain size distribution, surface roughness, water absorption, unit weight and crushing strength. The physical and mechanical properties of these aggregates were investigated by using conventional soil mechanics tests. Interface tests between lightweight aggregates and concrete showed that the effects of grain crushing, particle shape and the surface roughness of aggregates pla...