Analysis of elongation variance of tendons using stress-strain graphs
- Dundu, Morgan, Rupieper, Sebastian
- Authors: Dundu, Morgan , Rupieper, Sebastian
- Date: 2014
- Subjects: South African Design Standards , Tendons (Prestressed concrete) , Bonded tendons , Building materials
- Type: Article
- Identifier: uj:5079 , http://hdl.handle.net/10210/13650
- Description: The South African design standards (SANS 2001-CC1 and COLTO) prescribes an elongation variation limit of ±6% and an average variation limit of ±3%. Most often these limits are exceeded in practice. If the elongation variation of a tendon falls outside the prescribed elongation limits it must be assessed by the engineer. This paper analyses data of bonded tendons from post-tensioned structures. The aim of this study is to explain the elongation variance of tendons in post-tensioned structures using selected stress-strain graphs. These structures include a reservoir (Mthatha 1-10) and a viaduct (Gautrain Jean Avenue P80).
- Full Text:
- Authors: Dundu, Morgan , Rupieper, Sebastian
- Date: 2014
- Subjects: South African Design Standards , Tendons (Prestressed concrete) , Bonded tendons , Building materials
- Type: Article
- Identifier: uj:5079 , http://hdl.handle.net/10210/13650
- Description: The South African design standards (SANS 2001-CC1 and COLTO) prescribes an elongation variation limit of ±6% and an average variation limit of ±3%. Most often these limits are exceeded in practice. If the elongation variation of a tendon falls outside the prescribed elongation limits it must be assessed by the engineer. This paper analyses data of bonded tendons from post-tensioned structures. The aim of this study is to explain the elongation variance of tendons in post-tensioned structures using selected stress-strain graphs. These structures include a reservoir (Mthatha 1-10) and a viaduct (Gautrain Jean Avenue P80).
- Full Text:
Bottom ash and fly ash wastes as alkalinising reagents for neutralising acid mine drainage
- Ekolu, Stephen O., Diop, Souleymane, Azene, Firehiwot
- Authors: Ekolu, Stephen O. , Diop, Souleymane , Azene, Firehiwot
- Date: 2012
- Subjects: Acid mine drainage , Bottom ash , Fly ash , Coal ash
- Type: Book chapter
- Identifier: http://ujcontent.uj.ac.za8080/10210/370290 , uj:5024 , http://hdl.handle.net/10210/13461
- Description: Preliminary investigation was conducted to evaluate the utilization of bottom ash and fly ash by-products on a study limited to their role as alkalizing reagents, with the ultimate objective of examining their potential use for insitu treatment of acid mine drainage (AMD) in South African mines. Bottom ash (BA) and fly ash (FA) obtained from a coal-powered electricity generation station were used in varied combined proportions of 100/0, 90/10, 70/30 BA:FA reagent mixtures and used to conduct neutralization tests done at mix proportions varied from 20:1 to 1:1 AMD to reagent mixtures. Three types of acid mine drainage water from an underground gold mine (AMD-Wz), gold tailings dam (AMD-Lc) and a coal mine (AMD-MpK) were used in the investigation. Water quality tests were carried out before and after the neutralisation treatment. It was found that both bottom ash and fly ash are effective alkalinising reagents for neutralising AMD. The materials were found to be most effective when mixed at a ratio no greater than 5:1 of mine water to reagent. Use of the coal ash wastes effectively removed up to 99% of iron from the AMD. The sulphate concentration was also reduced by the treatment but it remained fairly elevated. Manganese concentration reduced as the pH of the treated water increased, reaching a negliglible concentration of < 1.0 mg/l at pH ≥ 11. Further investigations are underway to examine leaching and weathering characteristics of the reagents.
- Full Text:
- Authors: Ekolu, Stephen O. , Diop, Souleymane , Azene, Firehiwot
- Date: 2012
- Subjects: Acid mine drainage , Bottom ash , Fly ash , Coal ash
- Type: Book chapter
- Identifier: http://ujcontent.uj.ac.za8080/10210/370290 , uj:5024 , http://hdl.handle.net/10210/13461
- Description: Preliminary investigation was conducted to evaluate the utilization of bottom ash and fly ash by-products on a study limited to their role as alkalizing reagents, with the ultimate objective of examining their potential use for insitu treatment of acid mine drainage (AMD) in South African mines. Bottom ash (BA) and fly ash (FA) obtained from a coal-powered electricity generation station were used in varied combined proportions of 100/0, 90/10, 70/30 BA:FA reagent mixtures and used to conduct neutralization tests done at mix proportions varied from 20:1 to 1:1 AMD to reagent mixtures. Three types of acid mine drainage water from an underground gold mine (AMD-Wz), gold tailings dam (AMD-Lc) and a coal mine (AMD-MpK) were used in the investigation. Water quality tests were carried out before and after the neutralisation treatment. It was found that both bottom ash and fly ash are effective alkalinising reagents for neutralising AMD. The materials were found to be most effective when mixed at a ratio no greater than 5:1 of mine water to reagent. Use of the coal ash wastes effectively removed up to 99% of iron from the AMD. The sulphate concentration was also reduced by the treatment but it remained fairly elevated. Manganese concentration reduced as the pH of the treated water increased, reaching a negliglible concentration of < 1.0 mg/l at pH ≥ 11. Further investigations are underway to examine leaching and weathering characteristics of the reagents.
- Full Text:
Cold-formed circular hollow sections under axial compression
- Dundu, Morgan, Chabalala, Vongani
- Authors: Dundu, Morgan , Chabalala, Vongani
- Date: 2014
- Subjects: Columns, Concrete , Concrete slabs , Reinforced concrete construction , Concrete beams , South African Design Standards
- Type: Article
- Identifier: uj:5068 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13639
- Description: Two series of experiments were carried out to investigate the behaviour of pinned-ended circular hollow section (CHS) columns, subjected to axial compressive load. A total of 30 columns were tested in this investigation; 20 columns in Series 1 and 10 columns in Series 2. The outside diameter-to-thickness ratio (d/t) and the slenderness ratio (KL/r) ranged from 29.7 to 46.4 and 20.8 to 82.2 for Series 1, respectively, and from 55.0 to 62.9 and 10.7 to 34.9 for Series 2, respectively. In general, Series 1 columns failed by overall flexural buckling and, whilst Series 2 columns failed by local ring-type buckling. The test strengths of the columns were compared with the strengths predicted by the South African design standard (SANS10162-1) and the European design standard (EN 1993-1-1).
- Full Text:
- Authors: Dundu, Morgan , Chabalala, Vongani
- Date: 2014
- Subjects: Columns, Concrete , Concrete slabs , Reinforced concrete construction , Concrete beams , South African Design Standards
- Type: Article
- Identifier: uj:5068 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13639
- Description: Two series of experiments were carried out to investigate the behaviour of pinned-ended circular hollow section (CHS) columns, subjected to axial compressive load. A total of 30 columns were tested in this investigation; 20 columns in Series 1 and 10 columns in Series 2. The outside diameter-to-thickness ratio (d/t) and the slenderness ratio (KL/r) ranged from 29.7 to 46.4 and 20.8 to 82.2 for Series 1, respectively, and from 55.0 to 62.9 and 10.7 to 34.9 for Series 2, respectively. In general, Series 1 columns failed by overall flexural buckling and, whilst Series 2 columns failed by local ring-type buckling. The test strengths of the columns were compared with the strengths predicted by the South African design standard (SANS10162-1) and the European design standard (EN 1993-1-1).
- Full Text:
Compression tests of Mi Panels
- Authors: Bukasa, G. M. , Dundu, M.
- Date: 2014
- Subjects: Reinforced concrete construction , Concrete beams , Flexure , Concrete - Deterioration
- Type: Article
- Identifier: uj:5073 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13644
- Description: A number of compression tests of Mi Panels are presented. The use of lightweight Mi Panels as building system allows the reduction of construction time and waste in the building environment. The compression tests are performed to simulate the behaviour of the wall, when subjected to vertical loads from the roof. Two LVDTs were placed at mid-height of the panels during the compression tests, to record the lateral displacement. Mi Panels failed by fracturing into two parts at mid-height. No cracks in the panel were observed before overall flexural buckling failure. The tests showed that the panels are capable of carrying the required loads, and can be used in place of brick walls.
- Full Text:
- Authors: Bukasa, G. M. , Dundu, M.
- Date: 2014
- Subjects: Reinforced concrete construction , Concrete beams , Flexure , Concrete - Deterioration
- Type: Article
- Identifier: uj:5073 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13644
- Description: A number of compression tests of Mi Panels are presented. The use of lightweight Mi Panels as building system allows the reduction of construction time and waste in the building environment. The compression tests are performed to simulate the behaviour of the wall, when subjected to vertical loads from the roof. Two LVDTs were placed at mid-height of the panels during the compression tests, to record the lateral displacement. Mi Panels failed by fracturing into two parts at mid-height. No cracks in the panel were observed before overall flexural buckling failure. The tests showed that the panels are capable of carrying the required loads, and can be used in place of brick walls.
- Full Text:
Compressive strength and durability of fly ash stabilized dolomitic waste as a lightweight construction material
- Aneke, Ikechukwu F., Okonta, Felix N.
- Authors: Aneke, Ikechukwu F. , Okonta, Felix N.
- Date: 2014
- Subjects: Fly ash , Subsidences (Earth movements) - South Africa , Dolomitic waste
- Type: Article
- Identifier: uj:5075 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13646
- Description: Due to the seriousness of environmental pollution and the production of huge energy consuming building and construction materials, the development of new eco-friendly and energy saving building materials to overcome these issues has been gaining increasing attention. South Africa has largest number of dolomite deposits in Southern Africa, if not in the entire Africa. Nonetheless most of the dolomite in South Africa has some impurities of which they are neglected in dumping site (millions of tons). This paper looked at finding alternative use for this dolomitic waste (DW) by stabilizing this waste with another waste called fly ash (FA), introduction of gypsum as an activator will trigger a pozzolanic reaction in presences of water. As a result of this, the product of this reaction will be a useful material in construction and as well solve the difficulties i.e. environmental, social and cost often associated with storing and handling of this waste. This work went as far as providing an alternative for low-cost construction materials that can help deal with South African housing problems. The waste material was analyzed from geomaterial and geochemistry view point, the chemical reaction between these materials: dolomitic waste and fly ash were illustrated. The XRF, SEM and EDS of the reacted product were looked at, the strength gained by the reaction after sample preparation for 28 days were also shown. However various geotechnical laboratory experiments were conducted ranging from proctor compaction test, compressive strength test and a mathematical model was generated to predict the compressive strength and these results were compared to compressive strength values obtained from the laboratory.
- Full Text:
- Authors: Aneke, Ikechukwu F. , Okonta, Felix N.
- Date: 2014
- Subjects: Fly ash , Subsidences (Earth movements) - South Africa , Dolomitic waste
- Type: Article
- Identifier: uj:5075 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13646
- Description: Due to the seriousness of environmental pollution and the production of huge energy consuming building and construction materials, the development of new eco-friendly and energy saving building materials to overcome these issues has been gaining increasing attention. South Africa has largest number of dolomite deposits in Southern Africa, if not in the entire Africa. Nonetheless most of the dolomite in South Africa has some impurities of which they are neglected in dumping site (millions of tons). This paper looked at finding alternative use for this dolomitic waste (DW) by stabilizing this waste with another waste called fly ash (FA), introduction of gypsum as an activator will trigger a pozzolanic reaction in presences of water. As a result of this, the product of this reaction will be a useful material in construction and as well solve the difficulties i.e. environmental, social and cost often associated with storing and handling of this waste. This work went as far as providing an alternative for low-cost construction materials that can help deal with South African housing problems. The waste material was analyzed from geomaterial and geochemistry view point, the chemical reaction between these materials: dolomitic waste and fly ash were illustrated. The XRF, SEM and EDS of the reacted product were looked at, the strength gained by the reaction after sample preparation for 28 days were also shown. However various geotechnical laboratory experiments were conducted ranging from proctor compaction test, compressive strength test and a mathematical model was generated to predict the compressive strength and these results were compared to compressive strength values obtained from the laboratory.
- Full Text:
Concrete filled double skin circular tubes : a review
- Essopjee, Yoosuf, Dundu, Morgan
- Authors: Essopjee, Yoosuf , Dundu, Morgan
- Date: 2014
- Subjects: Prestressed concrete construction , Columns, Concrete , Plates, Iron and steel
- Type: Article
- Identifier: uj:5083 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13654
- Description: A review of the research conducted on the compressive strength of concrete filled double skin circular tubes (CFDSCT) columns is conducted. Variables of the CFDSCT considered in this review include the concrete strength, steel strength, inner and outer tube diameter, steel thickness and length of the stub columns. Test results show that the composite columns had compressive strengths of up to 41% higher than the sum of the individual strengths of the section. All the outer tubes of these composite columns by failed local buckling. A review of the design equations proposed are presented and discussed. The paper also identifies gaps for further research for these types of columns.
- Full Text:
- Authors: Essopjee, Yoosuf , Dundu, Morgan
- Date: 2014
- Subjects: Prestressed concrete construction , Columns, Concrete , Plates, Iron and steel
- Type: Article
- Identifier: uj:5083 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13654
- Description: A review of the research conducted on the compressive strength of concrete filled double skin circular tubes (CFDSCT) columns is conducted. Variables of the CFDSCT considered in this review include the concrete strength, steel strength, inner and outer tube diameter, steel thickness and length of the stub columns. Test results show that the composite columns had compressive strengths of up to 41% higher than the sum of the individual strengths of the section. All the outer tubes of these composite columns by failed local buckling. A review of the design equations proposed are presented and discussed. The paper also identifies gaps for further research for these types of columns.
- Full Text:
Condition assessment of a Johannesburg skyscraper
- Ekolu, Stephen, Van Ede, Willem F.
- Authors: Ekolu, Stephen , Van Ede, Willem F.
- Date: 2014
- Subjects: Skyscrapers - Evaluation
- Type: Book chapter
- Identifier: uj:5045 , ISSN 9781614994664 , http://hdl.handle.net/10210/13565
- Description: This paper presents a condition assessment conducted on a Johannesburg skyscraper. It had become apparent that concrete spalling occurred in areas of the top 11m of the Southern and Western facades of the reinforced concrete skyscraper constructed in the 1970’s. However, the extent of the problem was unknown. The only information available were two photographs showing spalled concrete and severely corroded reinforcement bars. Some literature search pertaining to the structure was conducted after which, visual inspection and mapping of spalled areas and cracks were conducted. This was followed by a cover meter survey, a half-cell potential survey, and the removal of 20 (twenty) cores for laboratory testing. It was found that the typical problems associated with carbonation and insufficient cover resulted in the corrosion of reinforcement which then led to the spalling observed.
- Full Text:
- Authors: Ekolu, Stephen , Van Ede, Willem F.
- Date: 2014
- Subjects: Skyscrapers - Evaluation
- Type: Book chapter
- Identifier: uj:5045 , ISSN 9781614994664 , http://hdl.handle.net/10210/13565
- Description: This paper presents a condition assessment conducted on a Johannesburg skyscraper. It had become apparent that concrete spalling occurred in areas of the top 11m of the Southern and Western facades of the reinforced concrete skyscraper constructed in the 1970’s. However, the extent of the problem was unknown. The only information available were two photographs showing spalled concrete and severely corroded reinforcement bars. Some literature search pertaining to the structure was conducted after which, visual inspection and mapping of spalled areas and cracks were conducted. This was followed by a cover meter survey, a half-cell potential survey, and the removal of 20 (twenty) cores for laboratory testing. It was found that the typical problems associated with carbonation and insufficient cover resulted in the corrosion of reinforcement which then led to the spalling observed.
- Full Text:
Effect of clay-concrete lining on canal seepage towards the drainage region – an analysis using Finite-Element method
- Solomon, Fitsum, Ekolu, Stephen
- Authors: Solomon, Fitsum , Ekolu, Stephen
- Date: 2014
- Subjects: Canals , Seepage , Drainage , Finite element method , Canals - Linings
- Type: Book chapter
- Identifier: uj:5049 , http://hdl.handle.net/10210/13588
- Description: For proper design of a drainage system that utilizes lined canals, knowledge of the seepage into a soil substrate/drainage region is necessary so that the drainage blanket and /or filter type and thickness, and the size of collector pipes can all be designed. The work presented in this paper is based on the problem of steady-state seepage from a hypothetical irrigation canal into the substrate/drainage region towards asymmetrical trapezoidal concrete-lined canal. The problem is solved using a finite element based software program to determine the flow volume into the drainage region. Typical values of soil permeability coefficients of single and two-layer subsoil from literature are used along with experimental results of a laboratory study done for the design seepage coefficient of clay-cement concrete as lining material. The water flow effect of canal seepage discharge analyzed shows that the effectiveness of canal lining in reducing seepage is less when drainage distance is large. This study may contribute towards a better understanding on design of hydraulic conductivity under hydraulic structures. It will systematically enumerate the many, often straightforward factors that determine coefficient of permeability for compliance purposes. This could also involve a re-estimation of the values of the permeability coefficient and the factors on which the coefficient depends.
- Full Text:
- Authors: Solomon, Fitsum , Ekolu, Stephen
- Date: 2014
- Subjects: Canals , Seepage , Drainage , Finite element method , Canals - Linings
- Type: Book chapter
- Identifier: uj:5049 , http://hdl.handle.net/10210/13588
- Description: For proper design of a drainage system that utilizes lined canals, knowledge of the seepage into a soil substrate/drainage region is necessary so that the drainage blanket and /or filter type and thickness, and the size of collector pipes can all be designed. The work presented in this paper is based on the problem of steady-state seepage from a hypothetical irrigation canal into the substrate/drainage region towards asymmetrical trapezoidal concrete-lined canal. The problem is solved using a finite element based software program to determine the flow volume into the drainage region. Typical values of soil permeability coefficients of single and two-layer subsoil from literature are used along with experimental results of a laboratory study done for the design seepage coefficient of clay-cement concrete as lining material. The water flow effect of canal seepage discharge analyzed shows that the effectiveness of canal lining in reducing seepage is less when drainage distance is large. This study may contribute towards a better understanding on design of hydraulic conductivity under hydraulic structures. It will systematically enumerate the many, often straightforward factors that determine coefficient of permeability for compliance purposes. This could also involve a re-estimation of the values of the permeability coefficient and the factors on which the coefficient depends.
- Full Text:
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
- Full Text:
- 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
- Full Text:
Effect of wetting and air curing durations on strength of stabilized sands
- Moatlhodi, Lerato J., Okonta, Felix N.
- Authors: Moatlhodi, Lerato J. , Okonta, Felix N.
- Date: 2014
- Subjects: Sandcrete blocks , Low-cost houses - South Africa , Building materials , High strength concrete , Portland cement , Fly ash
- Type: Article
- Identifier: uj:5076 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13647
- Description: Low cost houses in most developing countries are constructed from sandcrete blocks manufactured from sand-cement mortar. In South Africa, failure of many of these blocks has been experienced leading to collapse of the structures. Lack of sufficient compressive strength in the manufactured blocks was attributed as the main cause of the failures. The unconfined compressive strength (UCS) of sandcrete blocks can however be improved by curing the blocks under different conditions. Therefore the objective of this study was to evaluate the effect of different wetting and air drying durations would have on the strength and the stiffness of the cubes produced. Weakly cemented sand cubes, with different cement contents and cement-fly ash binder ratios compacted at the optimum moisture content, were prepared. The 28 days UCS was determined, modulus of elasticity and moisture contents of sample specimen was also determined. The results showed that curing cubes under water for 7 days and then air curing for 21 days yield maximum UCS and modulus of elasticity for sands cemented by plain Portland cement, and that 3 days under water curing produced maximum results for sands stabilized by cement-fly ash binder. It was however found that under water for 28 days results in minimum strength. Therefore the longer the cubes are cured under water minimum strengths were achieved.
- Full Text:
- Authors: Moatlhodi, Lerato J. , Okonta, Felix N.
- Date: 2014
- Subjects: Sandcrete blocks , Low-cost houses - South Africa , Building materials , High strength concrete , Portland cement , Fly ash
- Type: Article
- Identifier: uj:5076 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13647
- Description: Low cost houses in most developing countries are constructed from sandcrete blocks manufactured from sand-cement mortar. In South Africa, failure of many of these blocks has been experienced leading to collapse of the structures. Lack of sufficient compressive strength in the manufactured blocks was attributed as the main cause of the failures. The unconfined compressive strength (UCS) of sandcrete blocks can however be improved by curing the blocks under different conditions. Therefore the objective of this study was to evaluate the effect of different wetting and air drying durations would have on the strength and the stiffness of the cubes produced. Weakly cemented sand cubes, with different cement contents and cement-fly ash binder ratios compacted at the optimum moisture content, were prepared. The 28 days UCS was determined, modulus of elasticity and moisture contents of sample specimen was also determined. The results showed that curing cubes under water for 7 days and then air curing for 21 days yield maximum UCS and modulus of elasticity for sands cemented by plain Portland cement, and that 3 days under water curing produced maximum results for sands stabilized by cement-fly ash binder. It was however found that under water for 28 days results in minimum strength. Therefore the longer the cubes are cured under water minimum strengths were achieved.
- Full Text:
Effects of multi-walled carbon nanotubes on strength and interfacial transition zone of concrete
- Van Tonder, P., Mafokoane, T.T.
- Authors: Van Tonder, P. , Mafokoane, T.T.
- Date: 2014
- Subjects: Carbon nanotubes , Concrete - Mixing , Materials - Testing
- Type: Article
- Identifier: uj:5057 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13619
- Description: Multi-walled carbon nanotubes (MWCNTs) were used to try and eliminate the aggregate interfacial transition zone. Different concrete mixes were used in fixed proportions along with varying concentrations of CNTs. The CNTs were applied in different concentrations, namely, 0.05 wt%, 0.1 wt% and 0.2 wt%, per dry weight. CNTs were dispersed using sonication. Concrete specimens were tested for compressive, flexural and split-tensile strengths. For each test, thirteen mix designs were investigated which included untreated aggregates and CNTs, and treated aggregates and CNTs. The results were compared with the results of the control concrete. The results showed that the use of CNTs improves the compressive, flexural and split-tensile strengths. It was concluded that CNTs minimize the ITZ.
- Full Text:
- Authors: Van Tonder, P. , Mafokoane, T.T.
- Date: 2014
- Subjects: Carbon nanotubes , Concrete - Mixing , Materials - Testing
- Type: Article
- Identifier: uj:5057 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13619
- Description: Multi-walled carbon nanotubes (MWCNTs) were used to try and eliminate the aggregate interfacial transition zone. Different concrete mixes were used in fixed proportions along with varying concentrations of CNTs. The CNTs were applied in different concentrations, namely, 0.05 wt%, 0.1 wt% and 0.2 wt%, per dry weight. CNTs were dispersed using sonication. Concrete specimens were tested for compressive, flexural and split-tensile strengths. For each test, thirteen mix designs were investigated which included untreated aggregates and CNTs, and treated aggregates and CNTs. The results were compared with the results of the control concrete. The results showed that the use of CNTs improves the compressive, flexural and split-tensile strengths. It was concluded that CNTs minimize the ITZ.
- Full Text:
Effects of sulphuric acid on the compressive strength of blended cement-cassava peel ash concrete
- Olonade, Kolawole Adisa, Olajumoke, Akinropo Musiliu, Omotosho, Ayoade Oluwaseun, Oyekunle, Funso Ayobami
- Authors: Olonade, Kolawole Adisa , Olajumoke, Akinropo Musiliu , Omotosho, Ayoade Oluwaseun , Oyekunle, Funso Ayobami
- Date: 2014
- Subjects: Sulphuric acid , Reinforced concrete , Concrete - Mixing
- Type: Article
- Identifier: uj:5065 , http://hdl.handle.net/10210/13636
- Description: Influence of sulphuric acid on compressive strength of concrete made with blended cement-cassava peel ash was investigated in this study. This is with a view to determining the level of resistance of such concrete to acidic exposure. Cassava peel ash (CPA) prepared from uncontrolled burning was used to substitute cement at 5, 10, 15 and 20% by weight of cement as binder. Concrete mix proportions of 1:2:4 (batching by weight) were prepared with the slump value within 6010 mm while water-binder ratios (w/b) were being noted. A total of 90 cubes of the concrete mixture of sizes 150 mm were cast and cured in fresh water (as control), 0.5, 1.0 and 1.5 M concentrations of sulphuric acid solution (H2SO4) for 7, 28, 56 and 90 days. The compressive strength was determined at the expiration of each curing age. The results showed that the w/b increased with increase in the quantity of CPA in the mixture. Compressive strength of concrete made with cement-CPA as binder and cured in fresh water was comparable to that of normal concrete when up to 15% CPA was used, but relatively low strength was obtained when cured in H2SO4 solutions, depending on the quantity of CPA. Leaching of Porlandite in the concrete cubes was observed with worse condition in the case of concrete containing 20% CPA in sulphuric acid solution of 1.5 M. The compressive strength reduced with increase in concentrations of the acid as well as with increase in the content of the CPA. It is concluded that CPA did not mitigate the adverse effects of sulphuric acid on the compressive strength of blended cement-CPA concrete.
- Full Text:
- Authors: Olonade, Kolawole Adisa , Olajumoke, Akinropo Musiliu , Omotosho, Ayoade Oluwaseun , Oyekunle, Funso Ayobami
- Date: 2014
- Subjects: Sulphuric acid , Reinforced concrete , Concrete - Mixing
- Type: Article
- Identifier: uj:5065 , http://hdl.handle.net/10210/13636
- Description: Influence of sulphuric acid on compressive strength of concrete made with blended cement-cassava peel ash was investigated in this study. This is with a view to determining the level of resistance of such concrete to acidic exposure. Cassava peel ash (CPA) prepared from uncontrolled burning was used to substitute cement at 5, 10, 15 and 20% by weight of cement as binder. Concrete mix proportions of 1:2:4 (batching by weight) were prepared with the slump value within 6010 mm while water-binder ratios (w/b) were being noted. A total of 90 cubes of the concrete mixture of sizes 150 mm were cast and cured in fresh water (as control), 0.5, 1.0 and 1.5 M concentrations of sulphuric acid solution (H2SO4) for 7, 28, 56 and 90 days. The compressive strength was determined at the expiration of each curing age. The results showed that the w/b increased with increase in the quantity of CPA in the mixture. Compressive strength of concrete made with cement-CPA as binder and cured in fresh water was comparable to that of normal concrete when up to 15% CPA was used, but relatively low strength was obtained when cured in H2SO4 solutions, depending on the quantity of CPA. Leaching of Porlandite in the concrete cubes was observed with worse condition in the case of concrete containing 20% CPA in sulphuric acid solution of 1.5 M. The compressive strength reduced with increase in concentrations of the acid as well as with increase in the content of the CPA. It is concluded that CPA did not mitigate the adverse effects of sulphuric acid on the compressive strength of blended cement-CPA concrete.
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Factors that influence friction in tendons of unbonded post-tensioning systems
- Dundu, Morgan, Ward, Michelle
- Authors: Dundu, Morgan , Ward, Michelle
- Date: 2014
- Subjects: Tendons (Prestressed concrete) , Corrosion and anti-corrosives , Steel, Structural - Protection
- Type: Article
- Identifier: uj:5059 , ISSN 9781614994657 , ISSN 9781614994664 , http://hdl.handle.net/10210/13621
- Description: The coefficient of friction in an unbonded post tensioning system is influenced by many factors, and these factors include the thickness of lubricant or grease present in the system, clearance between the strand and the plastic sheath, surface characteristics of the strand and plastic sheath. In order to determine the effect of these factors, a series of friction tests were performed on two different diameters of strand, namely; 12.7 mm and 15.24 mm diameters. Through a regression analysis, it was found that the frictional force decreases with increase in the thickness of the grease and that friction increases with increase in the mass of the strand. The amount of friction was found to be dependent on the surface characteristics of the strand and plastic sheath, clearance between the plastic sheath and the strand and the extrusion process of the plastic sheath.
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- Authors: Dundu, Morgan , Ward, Michelle
- Date: 2014
- Subjects: Tendons (Prestressed concrete) , Corrosion and anti-corrosives , Steel, Structural - Protection
- Type: Article
- Identifier: uj:5059 , ISSN 9781614994657 , ISSN 9781614994664 , http://hdl.handle.net/10210/13621
- Description: The coefficient of friction in an unbonded post tensioning system is influenced by many factors, and these factors include the thickness of lubricant or grease present in the system, clearance between the strand and the plastic sheath, surface characteristics of the strand and plastic sheath. In order to determine the effect of these factors, a series of friction tests were performed on two different diameters of strand, namely; 12.7 mm and 15.24 mm diameters. Through a regression analysis, it was found that the frictional force decreases with increase in the thickness of the grease and that friction increases with increase in the mass of the strand. The amount of friction was found to be dependent on the surface characteristics of the strand and plastic sheath, clearance between the plastic sheath and the strand and the extrusion process of the plastic sheath.
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Flexural failure modes of steel plate-strengthened reinforced concrete elements
- Olajumoke, Akinropo Musiliu, Dundu, Morgan
- Authors: Olajumoke, Akinropo Musiliu , Dundu, Morgan
- Date: 2014
- Subjects: Reinforced concrete , Composite materials - Bonding - Congresses , Concrete beams - Maintenance and repair , Plates, Iron and steel
- Type: Article
- Identifier: uj:5071 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13642
- Description: Failure of plate strengthened flexural reinforced concrete (RC) member can be crushing of the concrete at the compression face or premature debonding of the plate from the concrete element at the tension face. Debonding can be classified into three groups; namely, intermediate crack debonding (ICD), delamination and plate-end debonding (PED). Intermediate crack debonding is caused by flexural or flexural-shear stress, and plate-end debonding and delamination are caused by interfacial stress. This paper reviews the failure modes of flexural strengthened RC elements in bending, using epoxy-bonded steel plates. It also attempts to establish the width-to-thickness ratios of plates that can achieve the full flexural strengths of the strengthened element and promote a ductile failure.
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- Authors: Olajumoke, Akinropo Musiliu , Dundu, Morgan
- Date: 2014
- Subjects: Reinforced concrete , Composite materials - Bonding - Congresses , Concrete beams - Maintenance and repair , Plates, Iron and steel
- Type: Article
- Identifier: uj:5071 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13642
- Description: Failure of plate strengthened flexural reinforced concrete (RC) member can be crushing of the concrete at the compression face or premature debonding of the plate from the concrete element at the tension face. Debonding can be classified into three groups; namely, intermediate crack debonding (ICD), delamination and plate-end debonding (PED). Intermediate crack debonding is caused by flexural or flexural-shear stress, and plate-end debonding and delamination are caused by interfacial stress. This paper reviews the failure modes of flexural strengthened RC elements in bending, using epoxy-bonded steel plates. It also attempts to establish the width-to-thickness ratios of plates that can achieve the full flexural strengths of the strengthened element and promote a ductile failure.
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Flexural tests of Mi Panels
- Authors: Bukasa, G. M. , Dundu, M.
- Date: 2014
- Subjects: Concrete beams , Flexure , Fiber cement , Fiber-reinforced concrete
- Type: Article
- Identifier: uj:5074 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13645
- Description: Two series of flexural tests on 2700x600x75 mm Mi Panels are presented. The inner core of these lightweight panels is made from mixing polystyrene beads called Neopor, high strength cement, and water. A chemical is used as binding agent to bond the inner core to the external fibre cement sheets of 4.5 mm thickness. The experimental programme consists of two series of tests with different loading conditions; the first series has line loads at one-third point from each end support and the second series has line loads, at quarter and three quarter span of the panels. All flexural tests are performed to simulate the behaviour of the wall, when subjected to wind loads. Although the panels failed by fracturing, the tests showed that the panels are capable of carrying the required loads.
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- Authors: Bukasa, G. M. , Dundu, M.
- Date: 2014
- Subjects: Concrete beams , Flexure , Fiber cement , Fiber-reinforced concrete
- Type: Article
- Identifier: uj:5074 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13645
- Description: Two series of flexural tests on 2700x600x75 mm Mi Panels are presented. The inner core of these lightweight panels is made from mixing polystyrene beads called Neopor, high strength cement, and water. A chemical is used as binding agent to bond the inner core to the external fibre cement sheets of 4.5 mm thickness. The experimental programme consists of two series of tests with different loading conditions; the first series has line loads at one-third point from each end support and the second series has line loads, at quarter and three quarter span of the panels. All flexural tests are performed to simulate the behaviour of the wall, when subjected to wind loads. Although the panels failed by fracturing, the tests showed that the panels are capable of carrying the required loads.
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Indicative tests on the effect of fly ash-β cyclodextrin composite on mortar and concrete permeability, sorptivity and porosity
- Ikotun, B.D., Fanourakis, George C., Mishra, S., Fanourakis, G.C.
- Authors: Ikotun, B.D. , Fanourakis, George C. , Mishra, S. , Fanourakis, G.C.
- Date: 2014
- Subjects: Fly ash , Composite materials , Polymer-impregnated concrete , Cyclodextrins , Concrete
- Type: Article
- Identifier: uj:5067 , http://hdl.handle.net/10210/13638
- Description: The focus of this research is to modify fly ash (FA) structure using β - cyclodextrin (β-CD) to increase its pozzolanic function in concrete. A previous study by the authors has shown that a composite is formed due to structural changes of fly ash by its interaction with cyclodextrin [1]. The objective of this paper was to assess the effect of fly ash-β cyclodextrin composite (FA-β-CD) on the transport properties (durability performance) of mortar and concrete, with a view to optimise its incorporation in concrete. The durability performance of mortar and concrete were assessed from the measurement of oxygen gas permeability, sorptivity and porosity using the South Africa durability index approach. Six mixtures were tested, comprising a control mixture (100% Portland Cement, PC), and five mixes containing the FA-β CD composite. All the composite mixes included 30 % FA by mass. The β-CD was mixed with the FA, in separate mixtures, in proportions of 0.1 %, 0.2 % and 0.5 %. Two sample preparation procedures were followed for FA-β-CD composites mixtures; firstly, physical mixtures of a pre-weighed amount of β-CD and FA were adopted for the dry mixtures and secondly, 0.0103M, 0.0206M and 0.0516Mβ-CD solutions were added to the concrete at the mixing stage for solution mixtures. The results indicated that FA-β-CD composite improved the flowability and durability performances when β-cyclodextrin (β-CD) was used at a lower percentage (0.1% and 0.2%).
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- Authors: Ikotun, B.D. , Fanourakis, George C. , Mishra, S. , Fanourakis, G.C.
- Date: 2014
- Subjects: Fly ash , Composite materials , Polymer-impregnated concrete , Cyclodextrins , Concrete
- Type: Article
- Identifier: uj:5067 , http://hdl.handle.net/10210/13638
- Description: The focus of this research is to modify fly ash (FA) structure using β - cyclodextrin (β-CD) to increase its pozzolanic function in concrete. A previous study by the authors has shown that a composite is formed due to structural changes of fly ash by its interaction with cyclodextrin [1]. The objective of this paper was to assess the effect of fly ash-β cyclodextrin composite (FA-β-CD) on the transport properties (durability performance) of mortar and concrete, with a view to optimise its incorporation in concrete. The durability performance of mortar and concrete were assessed from the measurement of oxygen gas permeability, sorptivity and porosity using the South Africa durability index approach. Six mixtures were tested, comprising a control mixture (100% Portland Cement, PC), and five mixes containing the FA-β CD composite. All the composite mixes included 30 % FA by mass. The β-CD was mixed with the FA, in separate mixtures, in proportions of 0.1 %, 0.2 % and 0.5 %. Two sample preparation procedures were followed for FA-β-CD composites mixtures; firstly, physical mixtures of a pre-weighed amount of β-CD and FA were adopted for the dry mixtures and secondly, 0.0103M, 0.0206M and 0.0516Mβ-CD solutions were added to the concrete at the mixing stage for solution mixtures. The results indicated that FA-β-CD composite improved the flowability and durability performances when β-cyclodextrin (β-CD) was used at a lower percentage (0.1% and 0.2%).
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Influence of a new viscosity modifying admixture on the performance of different superplasticizers
- Kazurikanyo, Jean-Bosco, Ekolu, Stephen
- Authors: Kazurikanyo, Jean-Bosco , Ekolu, Stephen
- Date: 2014
- Subjects: Cement - Viscosity , Plasticizers - Viscosity , Cement - Additives
- Type: Book chapter
- Identifier: uj:5038 , ISBN 9781614994664 , http://hdl.handle.net/10210/13558
- Description: An investigation was conducted on a new viscosity modifier, herein referred to as VMA, to determine its effects and compatibility with commercially available superplasticizers and local cements. Marsh cone tests were conducted on cement pastes to compare saturation points and the influence of the viscosity modifying admixture. It was found that the VMA gave improved results when used with a polycarboxylate-based superplasticizer and also reduces the required dosage of the superplasticizer needed to achieve specific fluidity. However, it was observed that the VMA showed no influence whatsoever, when used with the phosphonate based-superplasticizer. These findings underscore the importance of establishing compatibilities and interactions when more than one admixture is used in fresh concrete.
- Full Text:
- Authors: Kazurikanyo, Jean-Bosco , Ekolu, Stephen
- Date: 2014
- Subjects: Cement - Viscosity , Plasticizers - Viscosity , Cement - Additives
- Type: Book chapter
- Identifier: uj:5038 , ISBN 9781614994664 , http://hdl.handle.net/10210/13558
- Description: An investigation was conducted on a new viscosity modifier, herein referred to as VMA, to determine its effects and compatibility with commercially available superplasticizers and local cements. Marsh cone tests were conducted on cement pastes to compare saturation points and the influence of the viscosity modifying admixture. It was found that the VMA gave improved results when used with a polycarboxylate-based superplasticizer and also reduces the required dosage of the superplasticizer needed to achieve specific fluidity. However, it was observed that the VMA showed no influence whatsoever, when used with the phosphonate based-superplasticizer. These findings underscore the importance of establishing compatibilities and interactions when more than one admixture is used in fresh concrete.
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Infrared thermography as a diagnostic tool for subsurface assessments of concrete structures
- Scott, Matthew, Kruger, Deon
- Authors: Scott, Matthew , Kruger, Deon
- Date: 2014
- Subjects: Thermography , Testing concrete in structures , Infrared radiation - Congresses , Infrared - thermography
- Type: Article
- Identifier: uj:5060 , ISSN 9781614994657 , ISSN 9781614994664 , http://hdl.handle.net/10210/13623
- Description: This paper presents on-going research into the application of infrared (IR) thermography as a means of diagnosing the presence of delaminations in concrete structures. Infrared thermography, as a diagnostic tool, has demonstrated the potential to detect and visually display areas of delamination in concrete structures, offering a feasible supplement to the traditional techniques used for delamination surveys. However, the thermal gradients that develop in the concrete, and that are essential for the detection of the delaminations, are the result of the prevailing ambient conditions that surround the structure. Depending on the nature of these conditions, certain delaminations may be more visible than others while some may not be visible at all. Solar radiation has a significant effect on these thermal gradients and consequently, the temperature contrasts that develop between the areas of delaminated and intact concrete. This paper addresses the effect that solar radiation has on the ability of infrared thermography to detect and reveal areas of delamination in concrete structures. This effect has been studied by quantifying the temperature contrasts that developed at the surface of a concrete panel into which delamination type defects were intentionally embedded at different depths.
- Full Text:
- Authors: Scott, Matthew , Kruger, Deon
- Date: 2014
- Subjects: Thermography , Testing concrete in structures , Infrared radiation - Congresses , Infrared - thermography
- Type: Article
- Identifier: uj:5060 , ISSN 9781614994657 , ISSN 9781614994664 , http://hdl.handle.net/10210/13623
- Description: This paper presents on-going research into the application of infrared (IR) thermography as a means of diagnosing the presence of delaminations in concrete structures. Infrared thermography, as a diagnostic tool, has demonstrated the potential to detect and visually display areas of delamination in concrete structures, offering a feasible supplement to the traditional techniques used for delamination surveys. However, the thermal gradients that develop in the concrete, and that are essential for the detection of the delaminations, are the result of the prevailing ambient conditions that surround the structure. Depending on the nature of these conditions, certain delaminations may be more visible than others while some may not be visible at all. Solar radiation has a significant effect on these thermal gradients and consequently, the temperature contrasts that develop between the areas of delaminated and intact concrete. This paper addresses the effect that solar radiation has on the ability of infrared thermography to detect and reveal areas of delamination in concrete structures. This effect has been studied by quantifying the temperature contrasts that developed at the surface of a concrete panel into which delamination type defects were intentionally embedded at different depths.
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Isokinetic norms for ankle, knee, shoulder and forearm muscles in young South African men
- Authors: Lategan, Leon
- Date: 2011
- Subjects: Muscle strength , Ankle , Knee , Forearm , Shoulder , Isokinetics , Isokinetic peak torque
- Type: Article
- Identifier: uj:5742 , ISSN 0959-3020 , http://hdl.handle.net/10210/7738
- Description: Isokinetic test results are often evaluated against a norm or normal value. Previous research on isokinetics is prolific however, different populations present with different “normal” values. Thus, the aim of the present study was to establish isokinetic norms for the ankle, knee, shoulder, elbow and forearm joints in young, South African men. Methods: Four hundred and thirty eight (N = 438) young male participants (19.06 ± 1.86 yrs) were evaluated in terms of isokinetic peak torque of the ankle, knee, shoulder and forearm. A Cybex 340 isokinetic dynamometer was used to evaluate their concentric peak torque at a low velocity (30 or 60 /s); gravity was not corrected for. The data was tested for normality and the descriptive statistics were calculated. Percentile scores were subsequently constructed. Results: Normative values for peak torque, peak torque per body mass and agonistantagonist ratios were constructed for the ankle, knee, shoulder and forearm. Conclusions: Results from this study might provide useful norms for the clinical evaluation of low velocity, concentric peak torque in young males, when gravity correction is not performed.
- Full Text:
- Authors: Lategan, Leon
- Date: 2011
- Subjects: Muscle strength , Ankle , Knee , Forearm , Shoulder , Isokinetics , Isokinetic peak torque
- Type: Article
- Identifier: uj:5742 , ISSN 0959-3020 , http://hdl.handle.net/10210/7738
- Description: Isokinetic test results are often evaluated against a norm or normal value. Previous research on isokinetics is prolific however, different populations present with different “normal” values. Thus, the aim of the present study was to establish isokinetic norms for the ankle, knee, shoulder, elbow and forearm joints in young, South African men. Methods: Four hundred and thirty eight (N = 438) young male participants (19.06 ± 1.86 yrs) were evaluated in terms of isokinetic peak torque of the ankle, knee, shoulder and forearm. A Cybex 340 isokinetic dynamometer was used to evaluate their concentric peak torque at a low velocity (30 or 60 /s); gravity was not corrected for. The data was tested for normality and the descriptive statistics were calculated. Percentile scores were subsequently constructed. Results: Normative values for peak torque, peak torque per body mass and agonistantagonist ratios were constructed for the ankle, knee, shoulder and forearm. Conclusions: Results from this study might provide useful norms for the clinical evaluation of low velocity, concentric peak torque in young males, when gravity correction is not performed.
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Limits of elongation variation of tenadons in post-tensioning
- Dundu, Morgan, Rupieper, Sebastian
- Authors: Dundu, Morgan , Rupieper, Sebastian
- Date: 2014
- Subjects: Tendons (Prestressed concrete) , Prestressed concrete construction , South African Design Standards
- Type: Article
- Identifier: uj:5069 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13640
- Description: This paper analyses tensioning data obtained from a variety of projects that have been completed in South Africa in recent years in order to determine the causes of variation in elongation and suggest practical elongation limits. Current limits, prescribed by the South African standards (SANS 2001-CC1 and COLTO), of elongation variation limit of ±6% and an average elongation variation limit of ±3% are causing huge problems to the post-tensioning industry. The scatter of tendon elongation results is often greater than the range prescribed by these standards. This usually requires the contractor to re-tension the tendons at huge financial costs. In most cases the results obtained after re-tensioning are the same.
- Full Text:
- Authors: Dundu, Morgan , Rupieper, Sebastian
- Date: 2014
- Subjects: Tendons (Prestressed concrete) , Prestressed concrete construction , South African Design Standards
- Type: Article
- Identifier: uj:5069 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13640
- Description: This paper analyses tensioning data obtained from a variety of projects that have been completed in South Africa in recent years in order to determine the causes of variation in elongation and suggest practical elongation limits. Current limits, prescribed by the South African standards (SANS 2001-CC1 and COLTO), of elongation variation limit of ±6% and an average elongation variation limit of ±3% are causing huge problems to the post-tensioning industry. The scatter of tendon elongation results is often greater than the range prescribed by these standards. This usually requires the contractor to re-tension the tendons at huge financial costs. In most cases the results obtained after re-tensioning are the same.
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