Thin spray rock liners with different concentrations of nanoclays
- Van Tonder, P., Booysen, C.J, Van Tonder, P
- Authors: Van Tonder, P. , Booysen, C.J , Van Tonder, P
- Date: 2014
- Subjects: Nanostructured materials , Polymer-impregnated concrete , Reinforced concrete construction
- Type: Article
- Identifier: uj:5080 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13651
- Description: This study investigates the possibility of effectively replacing polymers in thin sprayed liners (TSL’s) with nanoclay particles. In the industry Nano particles are used in many different products to enhance their properties. The strength properties was analysed to see if the addition of nanoclays improve the strengths of the TSL product. Different concentrations of nanoclay were added to a standard TSL mixture in the place of polymer particles. The different composites were tested for Tensile Strength, Compression Strength, Shear Strength and Shear Bond Strength. Though there are other parameters to be tested, the study will only focus on those mentioned above, as they were considered to be the most important. The materials used for testing these characteristics were supplied by Oxyfibre. The mixtures have consisted of four different composites that included the standard mixture, 2% nanoclays, 4% nanoclays and 6% nanoclays.
- Full Text:
- Authors: Van Tonder, P. , Booysen, C.J , Van Tonder, P
- Date: 2014
- Subjects: Nanostructured materials , Polymer-impregnated concrete , Reinforced concrete construction
- Type: Article
- Identifier: uj:5080 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13651
- Description: This study investigates the possibility of effectively replacing polymers in thin sprayed liners (TSL’s) with nanoclay particles. In the industry Nano particles are used in many different products to enhance their properties. The strength properties was analysed to see if the addition of nanoclays improve the strengths of the TSL product. Different concentrations of nanoclay were added to a standard TSL mixture in the place of polymer particles. The different composites were tested for Tensile Strength, Compression Strength, Shear Strength and Shear Bond Strength. Though there are other parameters to be tested, the study will only focus on those mentioned above, as they were considered to be the most important. The materials used for testing these characteristics were supplied by Oxyfibre. The mixtures have consisted of four different composites that included the standard mixture, 2% nanoclays, 4% nanoclays and 6% nanoclays.
- Full Text:
The effects of natural and artificial UV exposure on the physical properties of synthetic turf used for various sports fields
- Zuzarte, Adriano Coutinho, Deon, KRUGER
- Authors: Zuzarte, Adriano Coutinho , Deon, KRUGER
- Date: 2014
- Subjects: Ultraviolet radiation , Sports facilities
- Type: Article
- Identifier: uj:5061 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13624
- Description: Since its induction at the Astrodome, in 1965 synthetic turf has been improved and adapted to now be accepted as a playing surface for a variety of sports. These sports include Rugby, Soccer and Field hockey. As synthetic turf is most likely destined for outdoor use it will be subject to Ultra Violet (UV) degradation in the form of Ultra Violet light band A (UVA), Ultra Violet light band B (UVB) or a combination of both. Synthetic turf is a polymer based material, specifically polyethylene for this study. For this reason it is useful to investigate how polyethylene degrades due to UV. Absorbed UV causes a break in the intermolecular bonds of the polyethylene, which leads to cracking, inhibiting the material to perform as initially intended. Colour change is also a consequence of extended exposure to UV. Various UV stabilizers are used, by manufacturers, in order to slow this process down. These however are largely dependent on the type of UV being exposed. Natural UV testing of new materials is time consuming, thus accelerated weathering testers such as the QUV/spray machines are used to simulate artificial UV and accelerate this process. A correlation between natural and artificial UV is sometimes difficult to achieve. For this reason both natural and artificial UV exposures were performed in this study. Through these various exposures to the samples, it was possible to indeed confirm that UV degrades synthetic turf as well as the processes leading to it. It was also confirmed that the samples would meet the sporting standards set out by the Internaltional Rugby Board (IRB), Fédération Internationale de Football Association (FIFA) and International Hockey Federation (FIH), for use as a playing surface. A correlation between natural and artificial UV in terms of colour change was achieved with UVA being found as thepredominant type of natural UV exposure in Johannesburg, during the winter months. Solutions were also provided to mitigate the degrading effects of UV on synthetic turf, these solutions would however need further investigation.
- Full Text:
- Authors: Zuzarte, Adriano Coutinho , Deon, KRUGER
- Date: 2014
- Subjects: Ultraviolet radiation , Sports facilities
- Type: Article
- Identifier: uj:5061 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13624
- Description: Since its induction at the Astrodome, in 1965 synthetic turf has been improved and adapted to now be accepted as a playing surface for a variety of sports. These sports include Rugby, Soccer and Field hockey. As synthetic turf is most likely destined for outdoor use it will be subject to Ultra Violet (UV) degradation in the form of Ultra Violet light band A (UVA), Ultra Violet light band B (UVB) or a combination of both. Synthetic turf is a polymer based material, specifically polyethylene for this study. For this reason it is useful to investigate how polyethylene degrades due to UV. Absorbed UV causes a break in the intermolecular bonds of the polyethylene, which leads to cracking, inhibiting the material to perform as initially intended. Colour change is also a consequence of extended exposure to UV. Various UV stabilizers are used, by manufacturers, in order to slow this process down. These however are largely dependent on the type of UV being exposed. Natural UV testing of new materials is time consuming, thus accelerated weathering testers such as the QUV/spray machines are used to simulate artificial UV and accelerate this process. A correlation between natural and artificial UV is sometimes difficult to achieve. For this reason both natural and artificial UV exposures were performed in this study. Through these various exposures to the samples, it was possible to indeed confirm that UV degrades synthetic turf as well as the processes leading to it. It was also confirmed that the samples would meet the sporting standards set out by the Internaltional Rugby Board (IRB), Fédération Internationale de Football Association (FIFA) and International Hockey Federation (FIH), for use as a playing surface. A correlation between natural and artificial UV in terms of colour change was achieved with UVA being found as thepredominant type of natural UV exposure in Johannesburg, during the winter months. Solutions were also provided to mitigate the degrading effects of UV on synthetic turf, these solutions would however need further investigation.
- Full Text:
Sulphate resistance of concrete made with moderately high alumina slag
- Ekolu, Stephen O., Ngwenya, Adam
- Authors: Ekolu, Stephen O. , Ngwenya, Adam
- Date: 2014
- Subjects: Blast furnaces , Slag cement - South Africa , Mortar - Congresses
- Type: Article
- Identifier: uj:5062 , ISBN 978-1-61499-466-4 , ISSN 9781614994657 , http://hdl.handle.net/10210/13625
- Description: This paper reports findings of ongoing investigation into the effect of high alumina ground granulated blast furnace slag (GGBS) on sulphate resistance of concrete. Slags used in most countries contain low alumina contents and provide high resistance to sulphate attack among other durability improvements. It is however known that slags of high alumina contents do not necessarily improve sulphate resistance but may otherwise adversely influence concrete performance. South African slags have moderately high alumina contents but hardly any studies have been conducted to determine its influence on sulphate resistance of concretes. In this investigation, commercially available slag widely used in South Africa was used. Mortar prisms 25 x 25 x 285 mm of 0.5 water-binder ratio incorporating 30%, 50%, 70% GGBS were prepared and immersed in sodium sulphate solutions of different concentrations of 28 g/L and 50 g/L as SO4. Expansion and mass change of the cementitious systems were monitored. Variables examined were compressive strengths prior to immersion in Na2SO4 solution, slag replacement levels, concentrations of sulphate solutions. It was found that the moderately high alumina slag improved resistance to sulphate attack in correspondence with increase in the replacement levels of the extender. Mixtures that were not cured to develop 20 MPa initial strength prior to exposure in Na2SO4 solution, showed elevated early age expansion while their cured counterparts did not expand. The long-term expansions of mixtures that had not been cured were much higher than expansions of the respective cured mixes. Interestingly, the use of GGBS in proportions exceeding 50% mitigated the adverse effects of early age expansions giving no long-term expansions in any of the mixtures containing the extender.
- Full Text:
- Authors: Ekolu, Stephen O. , Ngwenya, Adam
- Date: 2014
- Subjects: Blast furnaces , Slag cement - South Africa , Mortar - Congresses
- Type: Article
- Identifier: uj:5062 , ISBN 978-1-61499-466-4 , ISSN 9781614994657 , http://hdl.handle.net/10210/13625
- Description: This paper reports findings of ongoing investigation into the effect of high alumina ground granulated blast furnace slag (GGBS) on sulphate resistance of concrete. Slags used in most countries contain low alumina contents and provide high resistance to sulphate attack among other durability improvements. It is however known that slags of high alumina contents do not necessarily improve sulphate resistance but may otherwise adversely influence concrete performance. South African slags have moderately high alumina contents but hardly any studies have been conducted to determine its influence on sulphate resistance of concretes. In this investigation, commercially available slag widely used in South Africa was used. Mortar prisms 25 x 25 x 285 mm of 0.5 water-binder ratio incorporating 30%, 50%, 70% GGBS were prepared and immersed in sodium sulphate solutions of different concentrations of 28 g/L and 50 g/L as SO4. Expansion and mass change of the cementitious systems were monitored. Variables examined were compressive strengths prior to immersion in Na2SO4 solution, slag replacement levels, concentrations of sulphate solutions. It was found that the moderately high alumina slag improved resistance to sulphate attack in correspondence with increase in the replacement levels of the extender. Mixtures that were not cured to develop 20 MPa initial strength prior to exposure in Na2SO4 solution, showed elevated early age expansion while their cured counterparts did not expand. The long-term expansions of mixtures that had not been cured were much higher than expansions of the respective cured mixes. Interestingly, the use of GGBS in proportions exceeding 50% mitigated the adverse effects of early age expansions giving no long-term expansions in any of the mixtures containing the extender.
- Full Text:
Sulphate corrosion behaviour of high volume slag concrete
- Ekolu, Stephen O., Ngwenya, Adam
- Authors: Ekolu, Stephen O. , Ngwenya, Adam
- Date: 2014
- Subjects: Concrete - Mixing - Congresses , Concrete - Corrosion , Alumina cement
- Type: Article
- Identifier: uj:5063 , ISBN 9781614994657 , ISSN 9781614994664 , http://hdl.handle.net/10210/13626
- Description: Concrete mixes of water-cementitious ratio (w/c’s) = 0.45, 0.5, 0.65 were used to prepare 100 mm cubes and 75 x 75 x 285 mm prisms. Moderately high alumina slag was incorporated in proportions of 50 or 70% and the specimens immersed in sodium sulphate or magnesium sulphate solutions of 50 g/L as SO4. Emphasis in the study was to assess sulphate resistance using concrete samples and other non-conventional methods. Expansion measurements, mass loss and corrosion attack or physical deterioration of concrete were monitored for 69 weeks. It was found that the results of expansion, mass gain and corrosion were consistent for Na2SO4 solution, showing improved sulphate resistance with increase in ground granulated blast-furnace slag (GGBS) incorporation. The expansion observations under MgSO4, while showing increased resistance with use of GGBS, gave conflicting results between expansion on one hand and, mass gain and corrosion on the other with the most severe corrosion occurring in concrete containing the high 70% GGBS. The corrosion test method appears to give a more realistic indicator of physical damage under MgSO4 attack compared to expansion measurement.
- Full Text:
- Authors: Ekolu, Stephen O. , Ngwenya, Adam
- Date: 2014
- Subjects: Concrete - Mixing - Congresses , Concrete - Corrosion , Alumina cement
- Type: Article
- Identifier: uj:5063 , ISBN 9781614994657 , ISSN 9781614994664 , http://hdl.handle.net/10210/13626
- Description: Concrete mixes of water-cementitious ratio (w/c’s) = 0.45, 0.5, 0.65 were used to prepare 100 mm cubes and 75 x 75 x 285 mm prisms. Moderately high alumina slag was incorporated in proportions of 50 or 70% and the specimens immersed in sodium sulphate or magnesium sulphate solutions of 50 g/L as SO4. Emphasis in the study was to assess sulphate resistance using concrete samples and other non-conventional methods. Expansion measurements, mass loss and corrosion attack or physical deterioration of concrete were monitored for 69 weeks. It was found that the results of expansion, mass gain and corrosion were consistent for Na2SO4 solution, showing improved sulphate resistance with increase in ground granulated blast-furnace slag (GGBS) incorporation. The expansion observations under MgSO4, while showing increased resistance with use of GGBS, gave conflicting results between expansion on one hand and, mass gain and corrosion on the other with the most severe corrosion occurring in concrete containing the high 70% GGBS. The corrosion test method appears to give a more realistic indicator of physical damage under MgSO4 attack compared to expansion measurement.
- Full Text:
Simple criteria for evaluating sulphate attack in concrete
- Authors: Ekolu, Stephen
- Date: 2014
- Subjects: Concrete - Mixing , Blast furnaces , Slag cement , Concrete
- Type: Article
- Identifier: uj:5082 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13653
- Description: This paper attempts to analyse results from the standard test methods employed for sulphate attack and evaluates their correlations, consistency and contrasts, as well as physical observations. Data from expansions and mass change of 25 x25 x 285 mm mortar prisms and 75 x 75 x 285 mm concrete prisms were used. Mortar mixtures consisted of 1: 2.25: 0.5 cement to sand to water while concrete mixtures were of water-cementitious ratio (w/cm) of 0.45, 0.50, 0.65. Mixtures were made using CEM I 42.5N with or without 30, 50, 70% ground granulated blast furnace slag (GGBS) and stored in sodium sulphate solutions of 28 g/L and 50 g/L as SO4. Results show that ASTM C 1012 mortar expansion criteria of 0.10% corresponds to 1.2% mass gain. Similarly, concrete prism expansion criteria of 0.05% is equivalent to 0.75% mass gain. It is proposed that in the absence of expansion monitoring, the use of mass gain criteria of 1.2% mass in mortar prisms or 0.75% in concrete prisms may be sufficient for evaluating sulphate attack.
- Full Text:
- Authors: Ekolu, Stephen
- Date: 2014
- Subjects: Concrete - Mixing , Blast furnaces , Slag cement , Concrete
- Type: Article
- Identifier: uj:5082 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13653
- Description: This paper attempts to analyse results from the standard test methods employed for sulphate attack and evaluates their correlations, consistency and contrasts, as well as physical observations. Data from expansions and mass change of 25 x25 x 285 mm mortar prisms and 75 x 75 x 285 mm concrete prisms were used. Mortar mixtures consisted of 1: 2.25: 0.5 cement to sand to water while concrete mixtures were of water-cementitious ratio (w/cm) of 0.45, 0.50, 0.65. Mixtures were made using CEM I 42.5N with or without 30, 50, 70% ground granulated blast furnace slag (GGBS) and stored in sodium sulphate solutions of 28 g/L and 50 g/L as SO4. Results show that ASTM C 1012 mortar expansion criteria of 0.10% corresponds to 1.2% mass gain. Similarly, concrete prism expansion criteria of 0.05% is equivalent to 0.75% mass gain. It is proposed that in the absence of expansion monitoring, the use of mass gain criteria of 1.2% mass in mortar prisms or 0.75% in concrete prisms may be sufficient for evaluating sulphate attack.
- Full Text:
Radiological assessment of high density shielding concrete for neutron radiography
- Ekolu, Stephen, Ramushu, Mokgobi A.
- Authors: Ekolu, Stephen , Ramushu, Mokgobi A.
- Date: 2014
- Subjects: Concrete , Concrete - Mixing , Concrete blocks
- Type: Article
- Identifier: uj:5070 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13641
- Description: A radiation shield is a physical barrier placed between a source of ionizing radiation and the object to be protected from the radiation. In this research, concrete was selected as the best shielding material. An investigation was carried out to evaluate a specific concrete mixture developed in [1] for shielding of radiation energies. The high density shielding concrete (HDSC) concrete had 28-day compressive cube strength of 30 MPa, w/c (water/cementitious ratio) of 0.51 and density of 4231 kg/m3. It composed of CEM 52.5 N, silica fume, hematite aggregates, steel shots, colemanite and chemical admixtures. This paper presents an evaluation of the shielding properties of the HDSC using foil activation method. It is shown that the HDSC mixture achieved the desired shielding capabilities within the first 250 mm thickness of the concrete block.
- Full Text:
- Authors: Ekolu, Stephen , Ramushu, Mokgobi A.
- Date: 2014
- Subjects: Concrete , Concrete - Mixing , Concrete blocks
- Type: Article
- Identifier: uj:5070 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13641
- Description: A radiation shield is a physical barrier placed between a source of ionizing radiation and the object to be protected from the radiation. In this research, concrete was selected as the best shielding material. An investigation was carried out to evaluate a specific concrete mixture developed in [1] for shielding of radiation energies. The high density shielding concrete (HDSC) concrete had 28-day compressive cube strength of 30 MPa, w/c (water/cementitious ratio) of 0.51 and density of 4231 kg/m3. It composed of CEM 52.5 N, silica fume, hematite aggregates, steel shots, colemanite and chemical admixtures. This paper presents an evaluation of the shielding properties of the HDSC using foil activation method. It is shown that the HDSC mixture achieved the desired shielding capabilities within the first 250 mm thickness of the concrete block.
- Full Text:
Preliminary study of strength of coal composites
- Moatlhodi, Lerato J., Okonta, Felix N.
- Authors: Moatlhodi, Lerato J. , Okonta, Felix N.
- Date: 2014
- Subjects: Columns, Concrete , Composite materials , Pillar failure
- Type: Article
- Identifier: uj:5081 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13652
- Description: Large scale floor convergence and sudden failure of pillars in room-and pillar underground mining have been reported in various countries over many years. Failure of these mines has been attributed, amongst other causes, to the stiffness criterion used by the mining operators and most importantly mine design practices, that tend to reduce the width-to-height ratio i.e. slender pillars in pursuit of greater coal recovery yields, in order to maximize coal recovery in the seam. It is recorded that the room-and-pillar method can leave behind about 40% of the total coal available for mining. The current study seeks to determine the appropriate width-height ratio for coal composite and stabilized coal pillars. Pure coal was mixed with granular soil and stabilized with cement to form cylindrical composite columns which were crushed to determine their unconfined compressive strength at different width-to-height ratios. The strength increased with the increase in W/H of the columns. Increase in coal percentage in a composite reduces the strength. The stabilized coal pillars mobilized less strength than the composite pillars. Based on limited data, relationships amongst column strength W/H and mix ratios were formulated and are proposed for the estimation of strength of mine support structures. More data is however required to formulate a general regression equation.
- Full Text:
- Authors: Moatlhodi, Lerato J. , Okonta, Felix N.
- Date: 2014
- Subjects: Columns, Concrete , Composite materials , Pillar failure
- Type: Article
- Identifier: uj:5081 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13652
- Description: Large scale floor convergence and sudden failure of pillars in room-and pillar underground mining have been reported in various countries over many years. Failure of these mines has been attributed, amongst other causes, to the stiffness criterion used by the mining operators and most importantly mine design practices, that tend to reduce the width-to-height ratio i.e. slender pillars in pursuit of greater coal recovery yields, in order to maximize coal recovery in the seam. It is recorded that the room-and-pillar method can leave behind about 40% of the total coal available for mining. The current study seeks to determine the appropriate width-height ratio for coal composite and stabilized coal pillars. Pure coal was mixed with granular soil and stabilized with cement to form cylindrical composite columns which were crushed to determine their unconfined compressive strength at different width-to-height ratios. The strength increased with the increase in W/H of the columns. Increase in coal percentage in a composite reduces the strength. The stabilized coal pillars mobilized less strength than the composite pillars. Based on limited data, relationships amongst column strength W/H and mix ratios were formulated and are proposed for the estimation of strength of mine support structures. More data is however required to formulate a general regression equation.
- Full Text:
Potentiodynamic polarization study of the corrosion characteristics of acid mine drainage
- Ekolu, Stephen O., Diop, Souleymane, Azene, Firehiwot
- Authors: Ekolu, Stephen O. , Diop, Souleymane , Azene, Firehiwot
- Date: 2014
- Subjects: Acid mine drainage - South Africa , Concrete - Corrosion
- Type: Article
- Identifier: uj:5064 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13627
- Description: Potentiodynamic tests were carried out to evaluate the attacking characteristics of acid mine drainage (AMD) from South African mines. Tests were done using seven solutions of:- AMD water taken from the field and consisting of two AMD sources from the gold mines and two sources from the coal mines; sulphuric acid, distilled water, synthetic AMD prepared in the laboratory. Tests were done at normal room temperature of 23oC using mild steel and stainless steel samples. Tafel plots were generated and corrosion current (Icorr), corrosion potential (Ecorr), corrosion rates determined in each case. The corrosion rate of AMD from the coal mines was found to be similar to the corrosion of AMD from the gold tailings dam mine, both of which were significantly higher than the corrosion of AMD from the underground gold mine. It is, however, anticipated that the corrosion bevaviour could be different under static conditions and further investigations in this regard are being conducted.
- Full Text:
- Authors: Ekolu, Stephen O. , Diop, Souleymane , Azene, Firehiwot
- Date: 2014
- Subjects: Acid mine drainage - South Africa , Concrete - Corrosion
- Type: Article
- Identifier: uj:5064 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13627
- Description: Potentiodynamic tests were carried out to evaluate the attacking characteristics of acid mine drainage (AMD) from South African mines. Tests were done using seven solutions of:- AMD water taken from the field and consisting of two AMD sources from the gold mines and two sources from the coal mines; sulphuric acid, distilled water, synthetic AMD prepared in the laboratory. Tests were done at normal room temperature of 23oC using mild steel and stainless steel samples. Tafel plots were generated and corrosion current (Icorr), corrosion potential (Ecorr), corrosion rates determined in each case. The corrosion rate of AMD from the coal mines was found to be similar to the corrosion of AMD from the gold tailings dam mine, both of which were significantly higher than the corrosion of AMD from the underground gold mine. It is, however, anticipated that the corrosion bevaviour could be different under static conditions and further investigations in this regard are being conducted.
- Full Text:
Potential South African standard sand for cement mortar testing and research
- Authors: Ekolu, Stephen
- Date: 2014
- Subjects: Concrete - Testing , Strength of materials , Sand - Specifications - South Africa , Mortar - Testing
- Type: Book chapter
- Identifier: uj:5037 , ISBN 9781614994664 , http://hdl.handle.net/10210/13557
- Description: Mortars are used extensively in accelerated methods of testing the physical properties of cementitious materials. Mortar strength is invariably used to determine cement strength grade of cements and for general evaluation of material behavior, as typically employed in research and testing. Presently, the South African (SA) cement industry imports standard from Europe for cement testing purposes. This study was conducted to formulate South African standard sand that could be used to conduct mortar strength tests for compliance to specifications and for general research purposes. Two formulations of local South African silica sands, referenced as SA513S and SA413S, were developed to suit standard gradings. The formulated South African standard sands (SASS) where tested in comparison with European standard sand (ENSS) of EN196-1 and American graded standard sand (GSS) of ASTM C- 778. Following the formulation and grading of SASS, mortar mixtures of 1:3:0.5 cement to sand to water were cast in 50 mm cubes and tested for compressive strength for ages up to 90 days. Two types of cements were employed in the tests, the ordinary Portland cement CEM 1 42.5N and pozzolanic cement CEM V 32.5N. Comparison of the 28-day compressive strength results between the four SS types showed an excellent agreement, giving standard deviations of 1.96 and 2.51 for CEM I and CEM V. The flow results for the standard sand types varied, with EN196-1 giving the highest mortar flow followed by GSS sand and SA413S. The GSS and SA513S gave precisely the same flow results.
- Full Text:
- Authors: Ekolu, Stephen
- Date: 2014
- Subjects: Concrete - Testing , Strength of materials , Sand - Specifications - South Africa , Mortar - Testing
- Type: Book chapter
- Identifier: uj:5037 , ISBN 9781614994664 , http://hdl.handle.net/10210/13557
- Description: Mortars are used extensively in accelerated methods of testing the physical properties of cementitious materials. Mortar strength is invariably used to determine cement strength grade of cements and for general evaluation of material behavior, as typically employed in research and testing. Presently, the South African (SA) cement industry imports standard from Europe for cement testing purposes. This study was conducted to formulate South African standard sand that could be used to conduct mortar strength tests for compliance to specifications and for general research purposes. Two formulations of local South African silica sands, referenced as SA513S and SA413S, were developed to suit standard gradings. The formulated South African standard sands (SASS) where tested in comparison with European standard sand (ENSS) of EN196-1 and American graded standard sand (GSS) of ASTM C- 778. Following the formulation and grading of SASS, mortar mixtures of 1:3:0.5 cement to sand to water were cast in 50 mm cubes and tested for compressive strength for ages up to 90 days. Two types of cements were employed in the tests, the ordinary Portland cement CEM 1 42.5N and pozzolanic cement CEM V 32.5N. Comparison of the 28-day compressive strength results between the four SS types showed an excellent agreement, giving standard deviations of 1.96 and 2.51 for CEM I and CEM V. The flow results for the standard sand types varied, with EN196-1 giving the highest mortar flow followed by GSS sand and SA413S. The GSS and SA513S gave precisely the same flow results.
- Full Text:
Permeable reactive barriers for acid mine drainage treatment : a review
- Shabalala, Ayanda N., Ekolu, Stephen O., Diop, Souleymane
- Authors: Shabalala, Ayanda N. , Ekolu, Stephen O. , Diop, Souleymane
- Date: 2014
- Subjects: Acid mine drainage - Environmental aspects - South Africa , Acid mine drainage - Purification , Permeable reactive barriers , Water - Purification
- Type: Article
- Identifier: uj:5072 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13643
- Description: Contaminated water flowing from abandoned mines is one of the most significant contributors to water pollution. Acid mine drainage (AMD) can have severe impacts on aquatic resources, can stunt terrestrial plant growth and harm wetlands, contaminate groundwater, raise water treatment costs, and damage concrete and metal structures. Permeable reactive barriers (PRBs) are one of the passive treatment technologies widely accepted for sustainable in situ remediation of contaminated groundwater and may be used in the management of localised seepage plumes from mine residues that contaminate shallow groundwater. These barriers provide chemical interactions with AMD as the polluted water flows through it. The ability of PRBs to remediate contaminants is dependent on the type of reactive material used. Some of the reactive media remove contaminants through physical contact while others work by altering the biogeochemical processes in the treatment zone, thus providing conditions conducive for contaminant immobilization or (bio) degradation. A variety of materials has been employed to remove contaminants including heavy metals, chlorinated solvents, aromatic hydrocarbons, and pesticides. This paper gives an overview of the PRB technology, which includes the advantages and limitations of the PRB, the types of reactive materials used, laboratory treatability tests used to evaluate suitable reactive materials and to aid in the designing and the implementation of the PRB and the installations schemes used in PRB field application.
- Full Text:
- Authors: Shabalala, Ayanda N. , Ekolu, Stephen O. , Diop, Souleymane
- Date: 2014
- Subjects: Acid mine drainage - Environmental aspects - South Africa , Acid mine drainage - Purification , Permeable reactive barriers , Water - Purification
- Type: Article
- Identifier: uj:5072 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13643
- Description: Contaminated water flowing from abandoned mines is one of the most significant contributors to water pollution. Acid mine drainage (AMD) can have severe impacts on aquatic resources, can stunt terrestrial plant growth and harm wetlands, contaminate groundwater, raise water treatment costs, and damage concrete and metal structures. Permeable reactive barriers (PRBs) are one of the passive treatment technologies widely accepted for sustainable in situ remediation of contaminated groundwater and may be used in the management of localised seepage plumes from mine residues that contaminate shallow groundwater. These barriers provide chemical interactions with AMD as the polluted water flows through it. The ability of PRBs to remediate contaminants is dependent on the type of reactive material used. Some of the reactive media remove contaminants through physical contact while others work by altering the biogeochemical processes in the treatment zone, thus providing conditions conducive for contaminant immobilization or (bio) degradation. A variety of materials has been employed to remove contaminants including heavy metals, chlorinated solvents, aromatic hydrocarbons, and pesticides. This paper gives an overview of the PRB technology, which includes the advantages and limitations of the PRB, the types of reactive materials used, laboratory treatability tests used to evaluate suitable reactive materials and to aid in the designing and the implementation of the PRB and the installations schemes used in PRB field application.
- Full Text:
Palm kernel incinerated ash as low cost concrete component
- Agbenyeku, Emem-Obong Emmanuel, Okonta, Felix Ndubisi
- Authors: Agbenyeku, Emem-Obong Emmanuel , Okonta, Felix Ndubisi
- Date: 2014
- Subjects: Lightweight concrete , High strength concrete , Incineration
- Type: Article
- Identifier: uj:5058 , ISBN 9781614994657 , ISSN 9781614994664 , http://hdl.handle.net/10210/13620
- Description: The incorporation of commercially available fly ash (FA) as low cost material in concrete has long been established. Large quantities of FA are utilized for research and field applications because of the pozzolanic characteristics. One of many pozzolanic materials is palm kernel incinerated ash (PKIA). The abundance of PKIA as an agricultural waste material in West Africa obtained by the incineration of palm kernel husk and shells in milling boilers paved way for this study. Specimens containing 50%PKIA were cast and cured both in water and air and their compressive strength and shrinkage behaviours were investigated with and without the addition of superplasticizer (hydroxylated carboxylic (HC) acid) in comparison with controlled specimens containing 100%OPC. Results showed that the strength development in PKIA green concrete at all ages of curing; 7,14 and 28 days were lower than OPC concrete. On the addition of superplasticizer, strength of 36.9N/mm2 was observed for specimens with superplasticizer as against 31.7N/mm2 for specimens without superplasticizer on the 28day. The water curing method produced the best results while the predicted shrinkage strain of the green concrete in accordance to ACI 209R-92 standard was higher than the control specimens.
- Full Text:
- Authors: Agbenyeku, Emem-Obong Emmanuel , Okonta, Felix Ndubisi
- Date: 2014
- Subjects: Lightweight concrete , High strength concrete , Incineration
- Type: Article
- Identifier: uj:5058 , ISBN 9781614994657 , ISSN 9781614994664 , http://hdl.handle.net/10210/13620
- Description: The incorporation of commercially available fly ash (FA) as low cost material in concrete has long been established. Large quantities of FA are utilized for research and field applications because of the pozzolanic characteristics. One of many pozzolanic materials is palm kernel incinerated ash (PKIA). The abundance of PKIA as an agricultural waste material in West Africa obtained by the incineration of palm kernel husk and shells in milling boilers paved way for this study. Specimens containing 50%PKIA were cast and cured both in water and air and their compressive strength and shrinkage behaviours were investigated with and without the addition of superplasticizer (hydroxylated carboxylic (HC) acid) in comparison with controlled specimens containing 100%OPC. Results showed that the strength development in PKIA green concrete at all ages of curing; 7,14 and 28 days were lower than OPC concrete. On the addition of superplasticizer, strength of 36.9N/mm2 was observed for specimens with superplasticizer as against 31.7N/mm2 for specimens without superplasticizer on the 28day. The water curing method produced the best results while the predicted shrinkage strain of the green concrete in accordance to ACI 209R-92 standard was higher than the control specimens.
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Methods for flexural strengthening of reinforced concrete elements using steel plates
- Olajumoke, Akinropo Musiliu, Dundu, Morgan
- Authors: Olajumoke, Akinropo Musiliu , Dundu, Morgan
- Date: 2014
- Subjects: Concrete beams , Plates, Iron and steel , Reinforced concrete , Flexure
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/380017 , uj:5078 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13649
- Description: When reinforced concrete elements are incapable of safely sustaining the anticipated load, flexural strengthening may be necessary. Two major construction methods have been reported in literature for strengthening reinforced concrete (RC) elements in bending. These methods include Externally Bonded Reinforcement (EBR) and Near Surface Mounting (NSM). The aim of this paper is review these methods, including the extensive surface preparation that must be performed on bonded elements. Previous investigations have shown that these techniques are effective in salvaging old and distressed reinforced concrete structures. This paper identifies the problems associated with the utilisation of steel plates as strengthening material for RC elements in EBR and NSM techniques.
- Full Text:
- Authors: Olajumoke, Akinropo Musiliu , Dundu, Morgan
- Date: 2014
- Subjects: Concrete beams , Plates, Iron and steel , Reinforced concrete , Flexure
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/380017 , uj:5078 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13649
- Description: When reinforced concrete elements are incapable of safely sustaining the anticipated load, flexural strengthening may be necessary. Two major construction methods have been reported in literature for strengthening reinforced concrete (RC) elements in bending. These methods include Externally Bonded Reinforcement (EBR) and Near Surface Mounting (NSM). The aim of this paper is review these methods, including the extensive surface preparation that must be performed on bonded elements. Previous investigations have shown that these techniques are effective in salvaging old and distressed reinforced concrete structures. This paper identifies the problems associated with the utilisation of steel plates as strengthening material for RC elements in EBR and NSM techniques.
- Full Text:
Mechanical properties of green concrete with Palm Nut Shell as low cost aggregate
- Agbenyeku, Emem-Obong Emmanuel, Okonta, Felix Ndubisi
- Authors: Agbenyeku, Emem-Obong Emmanuel , Okonta, Felix Ndubisi
- Date: 2014
- Subjects: Sustainable construction , Prestressed concrete construction , Concrete - Testing , Building materials , Palm Nut Shell
- Type: Article
- Identifier: uj:5077 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13648
- Description: The cost saving benefits of aggregate replacement in concrete works are well documented. The utilization of Supplementary Aggregate Materials (SAMs) in concrete engineering without compromising standards in concrete works remain very attractive to both infrastructure developers and design engineers. However, there is continual search for low cost beneficial substitute materials. The mechanical properties of green concrete produced from Palm Nut Shell (PNS) as coarse aggregate was investigated. The abundance of PNS (light weight waste product of palm oil production) in West Africa created the impetus for the study. Series of laboratory tests such as; Slump, Compaction factor, Density, Schmidt hammer and Compressive strength tests were conducted on specimens of 10, 20, 30, 40 and 50% replacements of dry weight of PNS as coarse aggregate and specimens of natural aggregate as control sample. The specimens were cured at relative humidity (RH) of 95-100% and temperature (T) of 22-25oC in a chamber for periods of 7, 14, 21 and 28 days. The results showed the PNS samples to have relatively medium to high workability ranging from 24-47 mm for slump height and values of 0.85 to 0.90 for compaction factors. A general strength development was observed across the different samples with the PNS sample reaching strength of 48.7 N/mm2 at 28 days curing. The 50% replacement specimens which mobilized UCS of 28.7 N/mm2 met the requirement for lightweight concrete however, 30% is the optimum for a partial aggregate replacement in green concrete as UCS of 39.2 N/mm2 was mobilized in 28 days. Thus PNS is a suitable concrete constituent and can be a major cost reduction factor especially in low cost rural projects with streamlined loading requirements.
- Full Text:
- Authors: Agbenyeku, Emem-Obong Emmanuel , Okonta, Felix Ndubisi
- Date: 2014
- Subjects: Sustainable construction , Prestressed concrete construction , Concrete - Testing , Building materials , Palm Nut Shell
- Type: Article
- Identifier: uj:5077 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13648
- Description: The cost saving benefits of aggregate replacement in concrete works are well documented. The utilization of Supplementary Aggregate Materials (SAMs) in concrete engineering without compromising standards in concrete works remain very attractive to both infrastructure developers and design engineers. However, there is continual search for low cost beneficial substitute materials. The mechanical properties of green concrete produced from Palm Nut Shell (PNS) as coarse aggregate was investigated. The abundance of PNS (light weight waste product of palm oil production) in West Africa created the impetus for the study. Series of laboratory tests such as; Slump, Compaction factor, Density, Schmidt hammer and Compressive strength tests were conducted on specimens of 10, 20, 30, 40 and 50% replacements of dry weight of PNS as coarse aggregate and specimens of natural aggregate as control sample. The specimens were cured at relative humidity (RH) of 95-100% and temperature (T) of 22-25oC in a chamber for periods of 7, 14, 21 and 28 days. The results showed the PNS samples to have relatively medium to high workability ranging from 24-47 mm for slump height and values of 0.85 to 0.90 for compaction factors. A general strength development was observed across the different samples with the PNS sample reaching strength of 48.7 N/mm2 at 28 days curing. The 50% replacement specimens which mobilized UCS of 28.7 N/mm2 met the requirement for lightweight concrete however, 30% is the optimum for a partial aggregate replacement in green concrete as UCS of 39.2 N/mm2 was mobilized in 28 days. Thus PNS is a suitable concrete constituent and can be a major cost reduction factor especially in low cost rural projects with streamlined loading requirements.
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Material selection and mix design of radiation shielding concrete
- Ramushu, Mokgobi A., Ekolu, Stephen
- Authors: Ramushu, Mokgobi A. , Ekolu, Stephen
- Date: 2014
- Subjects: Shielding (Radiation) , Concrete , Aggregates (Building materials)
- Type: Book chapter
- Identifier: uj:5036 , http://hdl.handle.net/10210/13556
- Description: Based on the compiled literature and the availability of materials that could be used, concrete was selected as the best shielding material. Further work was carried out to develop a specific mixture that would shield the radioactive energies. The important special concrete ingredients that were considered in the mix design were high density aggregates and boron-containing aggregates. Various high density concrete mixtures of w/c (water/cementitious ratio) = 0.42, 0.45, 0.5 and 0.6, were prepared and adjusted appropriately in order to obtain the desired mix characteristics. The final (high density shielding concrete) mix produced was workable and cohesive with average 28- day compressive cube strength of 30 MPa, w/c = 0.51 and density of 4231 kg/m3. The concrete had high slump with a height and spread of 230 mm and 510 mm respectively. It was composed of CEM 52.5 N, silica fume, water, hematite sand, hematite stones, steel shots, colemanite and chemical admixtures.
- Full Text:
- Authors: Ramushu, Mokgobi A. , Ekolu, Stephen
- Date: 2014
- Subjects: Shielding (Radiation) , Concrete , Aggregates (Building materials)
- Type: Book chapter
- Identifier: uj:5036 , http://hdl.handle.net/10210/13556
- Description: Based on the compiled literature and the availability of materials that could be used, concrete was selected as the best shielding material. Further work was carried out to develop a specific mixture that would shield the radioactive energies. The important special concrete ingredients that were considered in the mix design were high density aggregates and boron-containing aggregates. Various high density concrete mixtures of w/c (water/cementitious ratio) = 0.42, 0.45, 0.5 and 0.6, were prepared and adjusted appropriately in order to obtain the desired mix characteristics. The final (high density shielding concrete) mix produced was workable and cohesive with average 28- day compressive cube strength of 30 MPa, w/c = 0.51 and density of 4231 kg/m3. The concrete had high slump with a height and spread of 230 mm and 510 mm respectively. It was composed of CEM 52.5 N, silica fume, water, hematite sand, hematite stones, steel shots, colemanite and chemical admixtures.
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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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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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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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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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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%).
- Full Text:
- 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%).
- Full Text:
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.
- Full Text:
- 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.
- Full Text: