Behaviour and load capacities of cast-in recoverable anchor screws
- Authors: Liebenberg, Willem Adriaan
- Date: 2014-05-29
- Subjects: Anchorage (Structural engineering) , Concrete construction , Fasteners - Design
- Type: Thesis
- Identifier: uj:11221 , http://hdl.handle.net/10210/10814
- Description: M.Tech. (Civil Engineering) , Recoverable anchor screws are widely used in the construction of massive concrete structures such as dams, channels, tunnels and multi-story buildings to fix temporary cantilever forms. Attempts have been made before to quantify the failure capacities of recoverable anchor screws. However, such tests were conducted and reported on more than 25 years ago and were limited to a small number of tests on concrete strengths not exceeding 20 MPa, whereas most concrete constructions now exceed such strengths. The aim of this dissertation was to review the existing theories on the use of concrete anchors in practice and to apply the appropriate theories to recoverable anchor screws. In doing so, the overall shear strength of these screws was determined by considering existing theoretical standards and norms, and by testing the tensile capacity in the laboratory. The failure behaviour of recoverable anchor screws in various concrete strengths and construction applications is reviewed and is discussed based on both theory and the laboratory results obtained. The empirical formulas derived for the practical use of recoverable anchor screws are presented in standard form. These formulas provide an easy reference for engineering professionals in practice to determine the load capacity of recoverable anchor screws in various concrete strengths and construction applications. In conclusion, the required future research on recoverable anchor screws is presented.
- Full Text:
- Authors: Liebenberg, Willem Adriaan
- Date: 2014-05-29
- Subjects: Anchorage (Structural engineering) , Concrete construction , Fasteners - Design
- Type: Thesis
- Identifier: uj:11221 , http://hdl.handle.net/10210/10814
- Description: M.Tech. (Civil Engineering) , Recoverable anchor screws are widely used in the construction of massive concrete structures such as dams, channels, tunnels and multi-story buildings to fix temporary cantilever forms. Attempts have been made before to quantify the failure capacities of recoverable anchor screws. However, such tests were conducted and reported on more than 25 years ago and were limited to a small number of tests on concrete strengths not exceeding 20 MPa, whereas most concrete constructions now exceed such strengths. The aim of this dissertation was to review the existing theories on the use of concrete anchors in practice and to apply the appropriate theories to recoverable anchor screws. In doing so, the overall shear strength of these screws was determined by considering existing theoretical standards and norms, and by testing the tensile capacity in the laboratory. The failure behaviour of recoverable anchor screws in various concrete strengths and construction applications is reviewed and is discussed based on both theory and the laboratory results obtained. The empirical formulas derived for the practical use of recoverable anchor screws are presented in standard form. These formulas provide an easy reference for engineering professionals in practice to determine the load capacity of recoverable anchor screws in various concrete strengths and construction applications. In conclusion, the required future research on recoverable anchor screws is presented.
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Effect of surface treatments on abrasion and permeation properties of clay concretes
- Solomon, Fitsum, Ekolu, Stephen
- Authors: Solomon, Fitsum , Ekolu, Stephen
- Date: 2014
- Subjects: Reinforced concrete , Concrete construction , Floors, Concrete - Design and construction
- Type: Article
- Identifier: uj:5066 , ISBN 9781614994657 , ISSN 9781614994664 , http://hdl.handle.net/10210/13637
- Description: The resistance of concrete surfaces to various types of wear can be a defining performance characteristic in certain applications. Some concrete structures are required to be abrasion-resistant; among them are dams, canals, roads, floors, footpaths, parking lots, and paths in parks. The work reported in this paper is based on a laboratory study of the concrete-surface treatments (CSTs) consisting of dry shake and screeding. Four control concrete mixtures were prepared with ordinary Portland cement (OPC), having a cement content (CC) of 350 kg/m3 at water-cementitious ratio (w/cc) = 0.70, 0.75; and 280 kg/m3 CC of w/cc = 0.80, 0.85. Other concrete mixtures were then prepared by substituting OPC in the control mixtures with 10, 20, 30, and 40% local raw clay. Compressive strength, abrasion resistance, and air permeability of the surface-treated concretes were measured at the ages of six months, while drying shrinkage was monitored for up to year. Drying shrinkage of concrete reduced with decrease in w/cc ratio and increased with increase in raw clay content. Among all the mixtures, the control concrete of w/cm ratio = 0.70 and the claycement concrete containing w/cm=0.80 at 70% OPC/30% raw clay showed the least and highest shrinkage increments respectively. Abrasion resistance of concrete, measured by the rotating-cutter method, increased with increasing clay content and decreasing compressive strength. However, abrasion performance results of clay-cement concrete mixtures with CSTs were generally higher. Air permeability of the concretes was measured and its relationship with the depth of abrasion of the concrete was examined
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- Authors: Solomon, Fitsum , Ekolu, Stephen
- Date: 2014
- Subjects: Reinforced concrete , Concrete construction , Floors, Concrete - Design and construction
- Type: Article
- Identifier: uj:5066 , ISBN 9781614994657 , ISSN 9781614994664 , http://hdl.handle.net/10210/13637
- Description: The resistance of concrete surfaces to various types of wear can be a defining performance characteristic in certain applications. Some concrete structures are required to be abrasion-resistant; among them are dams, canals, roads, floors, footpaths, parking lots, and paths in parks. The work reported in this paper is based on a laboratory study of the concrete-surface treatments (CSTs) consisting of dry shake and screeding. Four control concrete mixtures were prepared with ordinary Portland cement (OPC), having a cement content (CC) of 350 kg/m3 at water-cementitious ratio (w/cc) = 0.70, 0.75; and 280 kg/m3 CC of w/cc = 0.80, 0.85. Other concrete mixtures were then prepared by substituting OPC in the control mixtures with 10, 20, 30, and 40% local raw clay. Compressive strength, abrasion resistance, and air permeability of the surface-treated concretes were measured at the ages of six months, while drying shrinkage was monitored for up to year. Drying shrinkage of concrete reduced with decrease in w/cc ratio and increased with increase in raw clay content. Among all the mixtures, the control concrete of w/cm ratio = 0.70 and the claycement concrete containing w/cm=0.80 at 70% OPC/30% raw clay showed the least and highest shrinkage increments respectively. Abrasion resistance of concrete, measured by the rotating-cutter method, increased with increasing clay content and decreasing compressive strength. However, abrasion performance results of clay-cement concrete mixtures with CSTs were generally higher. Air permeability of the concretes was measured and its relationship with the depth of abrasion of the concrete was examined
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Mix design and alkali resistance of fly ash geopolymer binders
- Authors: Naghizadeh, Abdolhossein
- Date: 2019
- Subjects: Fly ash , Concrete construction
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/430766 , uj:37143
- Description: Abstract: The environmental impacts of ordinary Portland cement raise a need for alternative cements to be used as binders in concretes. A number of studies have shown that geopolymers could be employed as sustainable binders to replace the use of Portland cement in concrete. However, these new binder systems need to be investigated on different aspects before being employed at industrial scale. Fly ash is one of the common geopolymers, which has attracted research interest due to its wide availability for use as a starting material of acceptable performance. The present thesis addresses two different research challenges conducted in two phases. The first phase of this study deals with the strength of a fly ash - based geopolymer system, focusing on the development of a mix design method for fly ash - based geopolymers activated using different combinations of sodium hydroxide and sodium silicate solutions as alkali - activators. For this purpose, the effects of different mixture parameters on the strength of fly ash - based geopolymer pastes and mortars were investigated... , D.Phil. (Civil Engineering Science)
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- Authors: Naghizadeh, Abdolhossein
- Date: 2019
- Subjects: Fly ash , Concrete construction
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/430766 , uj:37143
- Description: Abstract: The environmental impacts of ordinary Portland cement raise a need for alternative cements to be used as binders in concretes. A number of studies have shown that geopolymers could be employed as sustainable binders to replace the use of Portland cement in concrete. However, these new binder systems need to be investigated on different aspects before being employed at industrial scale. Fly ash is one of the common geopolymers, which has attracted research interest due to its wide availability for use as a starting material of acceptable performance. The present thesis addresses two different research challenges conducted in two phases. The first phase of this study deals with the strength of a fly ash - based geopolymer system, focusing on the development of a mix design method for fly ash - based geopolymers activated using different combinations of sodium hydroxide and sodium silicate solutions as alkali - activators. For this purpose, the effects of different mixture parameters on the strength of fly ash - based geopolymer pastes and mortars were investigated... , D.Phil. (Civil Engineering Science)
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Validation of post-installed anchors tested to European technical approval guideline 001 in South African concrete using portable test equipment
- Authors: Sillman, C.R.
- Date: 2012-06-04
- Subjects: Ready-mixed concrete - Specifications - South Africa , Concrete construction , Concrete - Testing , Concrete - Quality control
- Type: Thesis
- Identifier: uj:2345 , http://hdl.handle.net/10210/4801
- Description: M. Phil. , The purpose of this research is to see if on-site portable pull-out tests in South Africa on post-installed chemical and mechanical fixings can produce similar results to internationally laboratory tested fixings. The method used in the field study was to use typical South African 25 MPa, 75 mm slump ready mix concrete as supplied by a reputable supplier and to test several types of fixings in common situations, some covered in the European Technical Approval Guidelines (ETAG) and some not. The results were analyzed against published international values and theoretical calculations for the fixings. The findings showed that the results produced using the portable equipment can show values similar to the published and theoretical values. It was also shown that this methodology can be used as a diagnostic tool to reveal installation errors. The pull-out test operator needs to be skilled to ensure a satisfactory outcome of the tests. The implications of the findings have direct bearing on: The on-site pullout testing of post installed anchors in South Africa; The diagnosing of bad anchor installation. And secondarily bearing on: The education of post-installed fixing installers and designers; The lack of standards for post-installed anchors in South Africa; The transportability of data from international research to South African conditions.
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- Authors: Sillman, C.R.
- Date: 2012-06-04
- Subjects: Ready-mixed concrete - Specifications - South Africa , Concrete construction , Concrete - Testing , Concrete - Quality control
- Type: Thesis
- Identifier: uj:2345 , http://hdl.handle.net/10210/4801
- Description: M. Phil. , The purpose of this research is to see if on-site portable pull-out tests in South Africa on post-installed chemical and mechanical fixings can produce similar results to internationally laboratory tested fixings. The method used in the field study was to use typical South African 25 MPa, 75 mm slump ready mix concrete as supplied by a reputable supplier and to test several types of fixings in common situations, some covered in the European Technical Approval Guidelines (ETAG) and some not. The results were analyzed against published international values and theoretical calculations for the fixings. The findings showed that the results produced using the portable equipment can show values similar to the published and theoretical values. It was also shown that this methodology can be used as a diagnostic tool to reveal installation errors. The pull-out test operator needs to be skilled to ensure a satisfactory outcome of the tests. The implications of the findings have direct bearing on: The on-site pullout testing of post installed anchors in South Africa; The diagnosing of bad anchor installation. And secondarily bearing on: The education of post-installed fixing installers and designers; The lack of standards for post-installed anchors in South Africa; The transportability of data from international research to South African conditions.
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