The deformation properties of concrete with classified Lethabo fly ash

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dc.contributor.advisorDe Kock, M Oen_ZA
dc.contributor.authorMukheibir, Pierre Victoren_ZA
dc.date.accessioned2015-12-28T05:59:29Z
dc.date.available2015-12-28T05:59:29Z
dc.date.issued1990en_ZA
dc.descriptionBibliography: pages 71-74.en_ZA
dc.description.abstractIt has become necessary to determine the magnitude of creep, shrinkage, elastic and thermal deformations of concrete as these characteristics determine the loss of prestressing in prestressed concrete and affect the deflections with time of large concrete sections. Much of the literature available on this topic has conflicting conclusions. In this research, the effect of fly ash was first investigated with regard to general concrete properties such as bleeding, early set, workability, mortar excess and compressive strength. Classified Lethabo fly ash and local Western Cape materials were used for this work. With the increase in the percentage fly ash present in the concrete mix, the water requirement was reduced in order to get the same workability. This characteristic reduced the amount of water available for bleeding. For a given C/W ratio the inclusion of fly ash in a concrete mix had no effect on the mortar excess. The early setting time was retarded for mixes with increasing percentages of fly ash. Higher cementitious material to water ratios were required for concrete with classified Lethabo fly ash than Ordinary Portland Cement mixes, to obtain the same 28 day compressive strength. The fly ash mixes had higher strength developments with time i.e. they have lower early strengths and higher long term strengths than OPC mixes for the same 28 day compressive strengths. Having developed a wide range of concrete mixes, the main investigation was done on specific deformation properties of concrete such as the elasticity, shrinkage, creep and thermal movement. The effect of different wet curing durations and testing ages on these properties were investigated. The elastic modulus was determined by both static and dynamic test methods. A relationship was established between the two methods to estimate the static modulus from the dynamic modulus, which was quicker to perform. In this thesis, the elastic modulus was not affected by the presence of fly ash. The elastic properties of the fly ash mixes was found to be similar to that of the OPC mixes of the same compressive strength. Similarly, the drying shrinkage and thermal movement were not affected noticeably by the presence of fly ash. The volume of aggregate was not a variable as it did not change when fly ash was added to the mix. An attempt was made to develop a test to determine the plastic shrinkage of an unrestrained sample. The effect of fly ash on the plastic shrinkage was not investigated fully. For the creep of concrete, it was established that mixes containing fly ash have lower creep factors than OPC concretes, although no clear trends were apparent for increasing percentages of fly ash. The effect of fly ash in pump mixes was also investigated and the same trends were apparent, although in general, the pump mixes had higher creep factors than the normal mixes. The curing of concrete is critical if good quality concrete is to be obtained. For all deformation properties, the longer a specimen was wet cured, the lower were the deformations. With longer wet curing, a larger volume of hydrated gel developed which gave higher compressive strengths and more rigidity within the matrix. The conclusion reached in this thesis was that the presence of classified Lethabo fly ash did not noticeably affect the deformation properties of the concrete for equivalent compressive strengths. Where some effects were noticed, the fly ash concretes displayed somewhat lower deformations.en_ZA
dc.identifier.apacitationMukheibir, P. V. (1990). <i>The deformation properties of concrete with classified Lethabo fly ash</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Civil Engineering. Retrieved from http://hdl.handle.net/11427/15944en_ZA
dc.identifier.chicagocitationMukheibir, Pierre Victor. <i>"The deformation properties of concrete with classified Lethabo fly ash."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Civil Engineering, 1990. http://hdl.handle.net/11427/15944en_ZA
dc.identifier.citationMukheibir, P. 1990. The deformation properties of concrete with classified Lethabo fly ash. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Mukheibir, Pierre Victor AB - It has become necessary to determine the magnitude of creep, shrinkage, elastic and thermal deformations of concrete as these characteristics determine the loss of prestressing in prestressed concrete and affect the deflections with time of large concrete sections. Much of the literature available on this topic has conflicting conclusions. In this research, the effect of fly ash was first investigated with regard to general concrete properties such as bleeding, early set, workability, mortar excess and compressive strength. Classified Lethabo fly ash and local Western Cape materials were used for this work. With the increase in the percentage fly ash present in the concrete mix, the water requirement was reduced in order to get the same workability. This characteristic reduced the amount of water available for bleeding. For a given C/W ratio the inclusion of fly ash in a concrete mix had no effect on the mortar excess. The early setting time was retarded for mixes with increasing percentages of fly ash. Higher cementitious material to water ratios were required for concrete with classified Lethabo fly ash than Ordinary Portland Cement mixes, to obtain the same 28 day compressive strength. The fly ash mixes had higher strength developments with time i.e. they have lower early strengths and higher long term strengths than OPC mixes for the same 28 day compressive strengths. Having developed a wide range of concrete mixes, the main investigation was done on specific deformation properties of concrete such as the elasticity, shrinkage, creep and thermal movement. The effect of different wet curing durations and testing ages on these properties were investigated. The elastic modulus was determined by both static and dynamic test methods. A relationship was established between the two methods to estimate the static modulus from the dynamic modulus, which was quicker to perform. In this thesis, the elastic modulus was not affected by the presence of fly ash. The elastic properties of the fly ash mixes was found to be similar to that of the OPC mixes of the same compressive strength. Similarly, the drying shrinkage and thermal movement were not affected noticeably by the presence of fly ash. The volume of aggregate was not a variable as it did not change when fly ash was added to the mix. An attempt was made to develop a test to determine the plastic shrinkage of an unrestrained sample. The effect of fly ash on the plastic shrinkage was not investigated fully. For the creep of concrete, it was established that mixes containing fly ash have lower creep factors than OPC concretes, although no clear trends were apparent for increasing percentages of fly ash. The effect of fly ash in pump mixes was also investigated and the same trends were apparent, although in general, the pump mixes had higher creep factors than the normal mixes. The curing of concrete is critical if good quality concrete is to be obtained. For all deformation properties, the longer a specimen was wet cured, the lower were the deformations. With longer wet curing, a larger volume of hydrated gel developed which gave higher compressive strengths and more rigidity within the matrix. The conclusion reached in this thesis was that the presence of classified Lethabo fly ash did not noticeably affect the deformation properties of the concrete for equivalent compressive strengths. Where some effects were noticed, the fly ash concretes displayed somewhat lower deformations. DA - 1990 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1990 T1 - The deformation properties of concrete with classified Lethabo fly ash TI - The deformation properties of concrete with classified Lethabo fly ash UR - http://hdl.handle.net/11427/15944 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/15944
dc.identifier.vancouvercitationMukheibir PV. The deformation properties of concrete with classified Lethabo fly ash. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Civil Engineering, 1990 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/15944en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Civil Engineeringen_ZA
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherCivil Engineeringen_ZA
dc.subject.otherConcreteen_ZA
dc.titleThe deformation properties of concrete with classified Lethabo fly ashen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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