The use of high performance concrete in construction has been enhanced by the use of pozzolanic materials. However, the use of these materials has not been optimized. Such optimization may be achieved by a systematic increase in the amount and combination of pozzolanic material additions, with accompanying studies of their effects on the mechanical, durability and microstructural characteristics of blended concrete. This work evaluated various concrete durability issues by studying systematic increases of pozzolanic materials such as fly ash and blast furnace slag (BFS) in the range of 25, 50 and 70%, and silica fume at 10% of total cementitious materials, forming various binary and ternary concrete blends. The concrete specimens were cured for a period of seven days after demoulding in line with widely practiced commercial curing procedures. The research explored the role and effectiveness of various binary and ternary blends of pozzolanic materials on the mechanical, durability and microstructural characteristics of concrete. Durability was evaluated by two independent rapid chloride permeability tests measured as charge passed and chloride conductivity from the RCPT and UCT tests respectively. These two rapid tests were coupled with long-term ponding tests to evaluate chloride ingress and the extent of corrosion for a period of two years. Further durability tests such as carbonation, drying shrinkage and porosity of these blends were also undertaken. This study also utilized micro-analytical techniques such as X-ray diffraction and Scanning Electron Microscopy to follow the hydration mechanism in various binary and ternary blends. Statistical significance testing was used to analyse and confirm all experimental results and conclusions. It is well known that a level of caution is exercised in the construction industry in the use of ternary blends. This study aims to evaluate the durability aspects of ternary concrete blends, in addition to binary blends, for resistance to chloride, corrosion, carbonation attacks and provide recommendations relating to the limits of blending level, as well as exposure conditions for blended concretes, based on the results of this study. It is expected that this will fill a major knowledge gap observed in the concrete industry. A comparison of two rapid chloride permeability tests such as UCT and RCPT indicates that the UCT test is easy and practicable, and does not contradict results obtained in the standard RCPT. However, the statistical significance of results obtained for some blends was only able to be established by using the RCPT. This effect can be attributed to the larger size specimens compared to UCT. The recommended blend to acquire both early-age and long-term strength development in fly ash is the ternary blends comprising 10% silica fume and 25% fly ash cast using lower w/b ratio. In addition, the same blend exhibited lower carbonation depth, lower charge passed from RCPT, lower chloride ingress and higher corrosion resistance characteristics from long-term ponding test compared to other blends of fly ash. In BFS blends, an increase in compressive strength was observed only in the specimens of 25% BFS compared to other higher percentage blends, while the higher addition of 50 and 70% replacement showed no significant difference in compressive strength between them and their corresponding ternary blends with addition of silica fume. The results of this study indicate that control (OPC) specimens cast with increased w/b ratio of 0.48 showed higher chloride ingress compared to both binary blends of 70% fly ash and 70% BFS specimens. This indicates that (OPC) cast using higher w/b ratio is to be avoided in chloride environments. On the other hand, though, the ternary blends of 10% silica fume and up to 50% fly ash exhibited lower chloride ingress compared to their respective binary blends of fly ash. However, these ternary blends exhibited lower compressive strength, more negative corrosion potential and higher corrosion rate, compared to the respective binary blends of 25% fly ash and its ternary blends. Therefore, the recommended blend observed in the long-term ponding test is the ternary blend of 25% fly ash and 10% silica fume. The recommended level of corrosion resistance in slag specimens is achieved by the use of ternary blends comprising silica fume at 10% added to the blend that contains up to 70% slag. However, the recommended level of slag for a lower carbonation effect is the use of a ternary blend comprising 50% slag and 10% silica fume (3B5S1) which showed a carbonation depth of 10.8 mm and a compressive strength of 53.2 MPa after 365 days of exposure. The drying shrinkage of concrete increased with the increase in fly ash and the same trend was observed in BFS specimens. However, the results were not significantly different between their respective blends. The extent of carbonation in fly ash specimens was higher compared to BFS blends specimens. This can be attributed to the formation of dusty and weak surfaces on the outer surface in addition to the excessive leaching of sodium chloride solution from the long-term ponding test in the former specimens compared to later. The high volume pozzolanic materials, irrespective of fly ash or BFS and addition of silica fume (70% fly ash and 10% silica fume, and 70% BFS and 10% silica fume), showed higher cumulative pore volume indicating that these blends with seven days of curing were not beneficial. These high volume ternary blends required prolonged curing to release portlandite from the hydration of cement to continue the pozzolanic reaction. This study has shown that 7-days curing of the pozzolanic concrete is inadequate if pozzolanic activity is to be invoked. This is particularly the case when it is expected that the concrete is likely to be subjected to a harsher than usual environment characterised by a dry atmosphere.

The use of high performance concrete in construction has been enhanced by the use of pozzolanic materials. However, the use of these materials has not been optimized. Such optimization may be achieved by a systematic increase in the amount and combination of pozzolanic material additions, with accompanying studies of their effects on the mechanical, durability and microstructural characteristics of blended concrete. This work evaluated various concrete durability issues by studying systematic increases of pozzolanic materials such as fly ash and blast furnace slag (BFS) in the range of 25, 50 and 70%, and silica fume at 10% of total cementitious materials, forming various binary and ternary concrete blends. The concrete specimens were cured for a period of seven days after demoulding in line with widely practiced commercial curing procedures. The research explored the role and effectiveness of various binary and ternary blends of pozzolanic materials on the mechanical, durability and microstructural characteristics of concrete. Durability was evaluated by two independent rapid chloride permeability tests measured as charge passed and chloride conductivity from the RCPT and UCT tests respectively. These two rapid tests were coupled with long-term ponding tests to evaluate chloride ingress and the extent of corrosion for a period of two years. Further durability tests such as carbonation, drying shrinkage and porosity of these blends were also undertaken. This study also utilized micro-analytical techniques such as X-ray diffraction and Scanning Electron Microscopy to follow the hydration mechanism in various binary and ternary blends. Statistical significance testing was used to analyse and confirm all experimental results and conclusions. It is well known that a level of caution is exercised in the construction industry in the use of ternary blends. This study aims to evaluate the durability aspects of ternary concrete blends, in addition to binary blends, for resistance to chloride, corrosion, carbonation attacks and provide recommendations relating to the limits of blending level, as well as exposure conditions for blended concretes, based on the results of this study. It is expected that this will fill a major knowledge gap observed in the concrete industry. A comparison of two rapid chloride permeability tests such as UCT and RCPT indicates that the UCT test is easy and practicable, and does not contradict results obtained in the standard RCPT. However, the statistical significance of results obtained for some blends was only able to be established by using the RCPT. This effect can be attributed to the larger size specimens compared to UCT. The recommended blend to acquire both early-age and long-term strength development in fly ash is the ternary blends comprising 10% silica fume and 25% fly ash cast using lower w/b ratio. In addition, the same blend exhibited lower carbonation depth, lower charge passed from RCPT, lower chloride ingress and higher corrosion resistance characteristics from long-term ponding test compared to other blends of fly ash. In BFS blends, an increase in compressive strength was observed only in the specimens of 25% BFS compared to other higher percentage blends, while the higher addition of 50 and 70% replacement showed no significant difference in compressive strength between them and their corresponding ternary blends with addition of silica fume. The results of this study indicate that control (OPC) specimens cast with increased w/b ratio of 0.48 showed higher chloride ingress compared to both binary blends of 70% fly ash and 70% BFS specimens. This indicates that (OPC) cast using higher w/b ratio is to be avoided in chloride environments. On the other hand, though, the ternary blends of 10% silica fume and up to 50% fly ash exhibited lower chloride ingress compared to their respective binary blends of fly ash. However, these ternary blends exhibited lower compressive strength, more negative corrosion potential and higher corrosion rate, compared to the respective binary blends of 25% fly ash and its ternary blends. Therefore, the recommended blend observed in the long-term ponding test is the ternary blend of 25% fly ash and 10% silica fume. The recommended level of corrosion resistance in slag specimens is achieved by the use of ternary blends comprising silica fume at 10% added to the blend that contains up to 70% slag. However, the recommended level of slag for a lower carbonation effect is the use of a ternary blend comprising 50% slag and 10% silica fume (3B5S1) which showed a carbonation depth of 10.8 mm and a compressive strength of 53.2 MPa after 365 days of exposure. The drying shrinkage of concrete increased with the increase in fly ash and the same trend was observed in BFS specimens. However, the results were not significantly different between their respective blends. The extent of carbonation in fly ash specimens was higher compared to BFS blends specimens. This can be attributed to the formation of dusty and weak surfaces on the outer surface in addition to the excessive leaching of sodium chloride solution from the long-term ponding test in the former specimens compared to later. The high volume pozzolanic materials, irrespective of fly ash or BFS and addition of silica fume (70% fly ash and 10% silica fume, and 70% BFS and 10% silica fume), showed higher cumulative pore volume indicating that these blends with seven days of curing were not beneficial. These high volume ternary blends required prolonged curing to release portlandite from the hydration of cement to continue the pozzolanic reaction. This study has shown that 7-days curing of the pozzolanic concrete is inadequate if pozzolanic activity is to be invoked. This is particularly the case when it is expected that the concrete is likely to be subjected to a harsher than usual environment characterised by a dry atmosphere.

The use of high performance concrete in construction has been enhanced by the use of pozzolanic materials. However, the use of these materials has not been optimized. Such optimization may be achieved by a systematic increase in the amount and combination of pozzolanic material additions, with accompanying studies of their effects on the mechanical, durability and microstructural characteristics of blended concrete. This work evaluated various concrete durability issues by studying systematic increases of pozzolanic materials such as fly ash and blast furnace slag (BFS) in the range of 25, 50 and 70%, and silica fume at 10% of total cementitious materials, forming various binary and ternary concrete blends. The concrete specimens were cured for a period of seven days after demoulding in line with widely practiced commercial curing procedures. The research explored the role and effectiveness of various binary and ternary blends of pozzolanic materials on the mechanical, durability and microstructural characteristics of concrete. Durability was evaluated by two independent rapid chloride permeability tests measured as charge passed and chloride conductivity from the RCPT and UCT tests respectively. These two rapid tests were coupled with long-term ponding tests to evaluate chloride ingress and the extent of corrosion for a period of two years. Further durability tests such as carbonation, drying shrinkage and porosity of these blends were also undertaken. This study also utilized micro-analytical techniques such as X-ray diffraction and Scanning Electron Microscopy to follow the hydration mechanism in various binary and ternary blends. Statistical significance testing was used to analyse and confirm all experimental results and conclusions. It is well known that a level of caution is exercised in the construction industry in the use of ternary blends. This study aims to evaluate the durability aspects of ternary concrete blends, in addition to binary blends, for resistance to chloride, corrosion, carbonation attacks and provide recommendations relating to the limits of blending level, as well as exposure conditions for blended concretes, based on the results of this study. It is expected that this will fill a major knowledge gap observed in the concrete industry. A comparison of two rapid chloride permeability tests such as UCT and RCPT indicates that the UCT test is easy and practicable, and does not contradict results obtained in the standard RCPT. However, the statistical significance of results obtained for some blends was only able to be established by using the RCPT. This effect can be attributed to the larger size specimens compared to UCT. The recommended blend to acquire both early-age and long-term strength development in fly ash is the ternary blends comprising 10% silica fume and 25% fly ash cast using lower w/b ratio. In addition, the same blend exhibited lower carbonation depth, lower charge passed from RCPT, lower chloride ingress and higher corrosion resistance characteristics from long-term ponding test compared to other blends of fly ash. In BFS blends, an increase in compressive strength was observed only in the specimens of 25% BFS compared to other higher percentage blends, while the higher addition of 50 and 70% replacement showed no significant difference in compressive strength between them and their corresponding ternary blends with addition of silica fume. The results of this study indicate that control (OPC) specimens cast with increased w/b ratio of 0.48 showed higher chloride ingress compared to both binary blends of 70% fly ash and 70% BFS specimens. This indicates that (OPC) cast using higher w/b ratio is to be avoided in chloride environments. On the other hand, though, the ternary blends of 10% silica fume and up to 50% fly ash exhibited lower chloride ingress compared to their respective binary blends of fly ash. However, these ternary blends exhibited lower compressive strength, more negative corrosion potential and higher corrosion rate, compared to the respective binary blends of 25% fly ash and its ternary blends. Therefore, the recommended blend observed in the long-term ponding test is the ternary blend of 25% fly ash and 10% silica fume. The recommended level of corrosion resistance in slag specimens is achieved by the use of ternary blends comprising silica fume at 10% added to the blend that contains up to 70% slag. However, the recommended level of slag for a lower carbonation effect is the use of a ternary blend comprising 50% slag and 10% silica fume (3B5S1) which showed a carbonation depth of 10.8 mm and a compressive strength of 53.2 MPa after 365 days of exposure. The drying shrinkage of concrete increased with the increase in fly ash and the same trend was observed in BFS specimens. However, the results were not significantly different between their respective blends. The extent of carbonation in fly ash specimens was higher compared to BFS blends specimens. This can be attributed to the formation of dusty and weak surfaces on the outer surface in addition to the excessive leaching of sodium chloride solution from the long-term ponding test in the former specimens compared to later. The high volume pozzolanic materials, irrespective of fly ash or BFS and addition of silica fume (70% fly ash and 10% silica fume, and 70% BFS and 10% silica fume), showed higher cumulative pore volume indicating that these blends with seven days of curing were not beneficial. These high volume ternary blends required prolonged curing to release portlandite from the hydration of cement to continue the pozzolanic reaction. This study has shown that 7-days curing of the pozzolanic concrete is inadequate if pozzolanic activity is to be invoked. This is particularly the case when it is expected that the concrete is likely to be subjected to a harsher than usual environment characterised by a dry atmosphere.

The use of high performance concrete in construction has been enhanced by the use of pozzolanic materials. However, the use of these materials has not been optimized. Such optimization may be achieved by a systematic increase in the amount and combination of pozzolanic material additions, with accompanying studies of their effects on the mechanical, durability and microstructural characteristics of blended concrete. This work evaluated various concrete durability issues by studying systematic increases of pozzolanic materials such as fly ash and blast furnace slag (BFS) in the range of 25, 50 and 70%, and silica fume at 10% of total cementitious materials, forming various binary and ternary concrete blends. The concrete specimens were cured for a period of seven days after demoulding in line with widely practiced commercial curing procedures. The research explored the role and effectiveness of various binary and ternary blends of pozzolanic materials on the mechanical, durability and microstructural characteristics of concrete. Durability was evaluated by two independent rapid chloride permeability tests measured as charge passed and chloride conductivity from the RCPT and UCT tests respectively. These two rapid tests were coupled with long-term ponding tests to evaluate chloride ingress and the extent of corrosion for a period of two years. Further durability tests such as carbonation, drying shrinkage and porosity of these blends were also undertaken. This study also utilized micro-analytical techniques such as X-ray diffraction and Scanning Electron Microscopy to follow the hydration mechanism in various binary and ternary blends. Statistical significance testing was used to analyse and confirm all experimental results and conclusions. It is well known that a level of caution is exercised in the construction industry in the use of ternary blends. This study aims to evaluate the durability aspects of ternary concrete blends, in addition to binary blends, for resistance to chloride, corrosion, carbonation attacks and provide recommendations relating to the limits of blending level, as well as exposure conditions for blended concretes, based on the results of this study. It is expected that this will fill a major knowledge gap observed in the concrete industry. A comparison of two rapid chloride permeability tests such as UCT and RCPT indicates that the UCT test is easy and practicable, and does not contradict results obtained in the standard RCPT. However, the statistical significance of results obtained for some blends was only able to be established by using the RCPT. This effect can be attributed to the larger size specimens compared to UCT. The recommended blend to acquire both early-age and long-term strength development in fly ash is the ternary blends comprising 10% silica fume and 25% fly ash cast using lower w/b ratio. In addition, the same blend exhibited lower carbonation depth, lower charge passed from RCPT, lower chloride ingress and higher corrosion resistance characteristics from long-term ponding test compared to other blends of fly ash. In BFS blends, an increase in compressive strength was observed only in the specimens of 25% BFS compared to other higher percentage blends, while the higher addition of 50 and 70% replacement showed no significant difference in compressive strength between them and their corresponding ternary blends with addition of silica fume. The results of this study indicate that control (OPC) specimens cast with increased w/b ratio of 0.48 showed higher chloride ingress compared to both binary blends of 70% fly ash and 70% BFS specimens. This indicates that (OPC) cast using higher w/b ratio is to be avoided in chloride environments. On the other hand, though, the ternary blends of 10% silica fume and up to 50% fly ash exhibited lower chloride ingress compared to their respective binary blends of fly ash. However, these ternary blends exhibited lower compressive strength, more negative corrosion potential and higher corrosion rate, compared to the respective binary blends of 25% fly ash and its ternary blends. Therefore, the recommended blend observed in the long-term ponding test is the ternary blend of 25% fly ash and 10% silica fume. The recommended level of corrosion resistance in slag specimens is achieved by the use of ternary blends comprising silica fume at 10% added to the blend that contains up to 70% slag. However, the recommended level of slag for a lower carbonation effect is the use of a ternary blend comprising 50% slag and 10% silica fume (3B5S1) which showed a carbonation depth of 10.8 mm and a compressive strength of 53.2 MPa after 365 days of exposure. The drying shrinkage of concrete increased with the increase in fly ash and the same trend was observed in BFS specimens. However, the results were not significantly different between their respective blends. The extent of carbonation in fly ash specimens was higher compared to BFS blends specimens. This can be attributed to the formation of dusty and weak surfaces on the outer surface in addition to the excessive leaching of sodium chloride solution from the long-term ponding test in the former specimens compared to later. The high volume pozzolanic materials, irrespective of fly ash or BFS and addition of silica fume (70% fly ash and 10% silica fume, and 70% BFS and 10% silica fume), showed higher cumulative pore volume indicating that these blends with seven days of curing were not beneficial. These high volume ternary blends required prolonged curing to release portlandite from the hydration of cement to continue the pozzolanic reaction. This study has shown that 7-days curing of the pozzolanic concrete is inadequate if pozzolanic activity is to be invoked. This is particularly the case when it is expected that the concrete is likely to be subjected to a harsher than usual environment characterised by a dry atmosphere.

The use of high performance concrete in construction has been enhanced by the use of pozzolanic materials. However, the use of these materials has not been optimized. Such optimization may be achieved by a systematic increase in the amount and combination of pozzolanic material additions, with accompanying studies of their effects on the mechanical, durability and microstructural characteristics of blended concrete. This work evaluated various concrete durability issues by studying systematic increases of pozzolanic materials such as fly ash and blast furnace slag (BFS) in the range of 25, 50 and 70%, and silica fume at 10% of total cementitious materials, forming various binary and ternary concrete blends. The concrete specimens were cured for a period of seven days after demoulding in line with widely practiced commercial curing procedures. The research explored the role and effectiveness of various binary and ternary blends of pozzolanic materials on the mechanical, durability and microstructural characteristics of concrete. Durability was evaluated by two independent rapid chloride permeability tests measured as charge passed and chloride conductivity from the RCPT and UCT tests respectively. These two rapid tests were coupled with long-term ponding tests to evaluate chloride ingress and the extent of corrosion for a period of two years. Further durability tests such as carbonation, drying shrinkage and porosity of these blends were also undertaken. This study also utilized micro-analytical techniques such as X-ray diffraction and Scanning Electron Microscopy to follow the hydration mechanism in various binary and ternary blends. Statistical significance testing was used to analyse and confirm all experimental results and conclusions. It is well known that a level of caution is exercised in the construction industry in the use of ternary blends. This study aims to evaluate the durability aspects of ternary concrete blends, in addition to binary blends, for resistance to chloride, corrosion, carbonation attacks and provide recommendations relating to the limits of blending level, as well as exposure conditions for blended concretes, based on the results of this study. It is expected that this will fill a major knowledge gap observed in the concrete industry. A comparison of two rapid chloride permeability tests such as UCT and RCPT indicates that the UCT test is easy and practicable, and does not contradict results obtained in the standard RCPT. However, the statistical significance of results obtained for some blends was only able to be established by using the RCPT. This effect can be attributed to the larger size specimens compared to UCT. The recommended blend to acquire both early-age and long-term strength development in fly ash is the ternary blends comprising 10% silica fume and 25% fly ash cast using lower w/b ratio. In addition, the same blend exhibited lower carbonation depth, lower charge passed from RCPT, lower chloride ingress and higher corrosion resistance characteristics from long-term ponding test compared to other blends of fly ash. In BFS blends, an increase in compressive strength was observed only in the specimens of 25% BFS compared to other higher percentage blends, while the higher addition of 50 and 70% replacement showed no significant difference in compressive strength between them and their corresponding ternary blends with addition of silica fume. The results of this study indicate that control (OPC) specimens cast with increased w/b ratio of 0.48 showed higher chloride ingress compared to both binary blends of 70% fly ash and 70% BFS specimens. This indicates that (OPC) cast using higher w/b ratio is to be avoided in chloride environments. On the other hand, though, the ternary blends of 10% silica fume and up to 50% fly ash exhibited lower chloride ingress compared to their respective binary blends of fly ash. However, these ternary blends exhibited lower compressive strength, more negative corrosion potential and higher corrosion rate, compared to the respective binary blends of 25% fly ash and its ternary blends. Therefore, the recommended blend observed in the long-term ponding test is the ternary blend of 25% fly ash and 10% silica fume. The recommended level of corrosion resistance in slag specimens is achieved by the use of ternary blends comprising silica fume at 10% added to the blend that contains up to 70% slag. However, the recommended level of slag for a lower carbonation effect is the use of a ternary blend comprising 50% slag and 10% silica fume (3B5S1) which showed a carbonation depth of 10.8 mm and a compressive strength of 53.2 MPa after 365 days of exposure. The drying shrinkage of concrete increased with the increase in fly ash and the same trend was observed in BFS specimens. However, the results were not significantly different between their respective blends. The extent of carbonation in fly ash specimens was higher compared to BFS blends specimens. This can be attributed to the formation of dusty and weak surfaces on the outer surface in addition to the excessive leaching of sodium chloride solution from the long-term ponding test in the former specimens compared to later. The high volume pozzolanic materials, irrespective of fly ash or BFS and addition of silica fume (70% fly ash and 10% silica fume, and 70% BFS and 10% silica fume), showed higher cumulative pore volume indicating that these blends with seven days of curing were not beneficial. These high volume ternary blends required prolonged curing to release portlandite from the hydration of cement to continue the pozzolanic reaction. This study has shown that 7-days curing of the pozzolanic concrete is inadequate if pozzolanic activity is to be invoked. This is particularly the case when it is expected that the concrete is likely to be subjected to a harsher than usual environment characterised by a dry atmosphere.

The use of high performance concrete in construction has been enhanced by the use of pozzolanic materials. However, the use of these materials has not been optimized. Such optimization may be achieved by a systematic increase in the amount and combination of pozzolanic material additions, with accompanying studies of their effects on the mechanical, durability and microstructural characteristics of blended concrete. This work evaluated various concrete durability issues by studying systematic increases of pozzolanic materials such as fly ash and blast furnace slag (BFS) in the range of 25, 50 and 70%, and silica fume at 10% of total cementitious materials, forming various binary and ternary concrete blends. The concrete specimens were cured for a period of seven days after demoulding in line with widely practiced commercial curing procedures. The research explored the role and effectiveness of various binary and ternary blends of pozzolanic materials on the mechanical, durability and microstructural characteristics of concrete. Durability was evaluated by two independent rapid chloride permeability tests measured as charge passed and chloride conductivity from the RCPT and UCT tests respectively. These two rapid tests were coupled with long-term ponding tests to evaluate chloride ingress and the extent of corrosion for a period of two years. Further durability tests such as carbonation, drying shrinkage and porosity of these blends were also undertaken. This study also utilized micro-analytical techniques such as X-ray diffraction and Scanning Electron Microscopy to follow the hydration mechanism in various binary and ternary blends. Statistical significance testing was used to analyse and confirm all experimental results and conclusions. It is well known that a level of caution is exercised in the construction industry in the use of ternary blends. This study aims to evaluate the durability aspects of ternary concrete blends, in addition to binary blends, for resistance to chloride, corrosion, carbonation attacks and provide recommendations relating to the limits of blending level, as well as exposure conditions for blended concretes, based on the results of this study. It is expected that this will fill a major knowledge gap observed in the concrete industry. A comparison of two rapid chloride permeability tests such as UCT and RCPT indicates that the UCT test is easy and practicable, and does not contradict results obtained in the standard RCPT. However, the statistical significance of results obtained for some blends was only able to be established by using the RCPT. This effect can be attributed to the larger size specimens compared to UCT. The recommended blend to acquire both early-age and long-term strength development in fly ash is the ternary blends comprising 10% silica fume and 25% fly ash cast using lower w/b ratio. In addition, the same blend exhibited lower carbonation depth, lower charge passed from RCPT, lower chloride ingress and higher corrosion resistance characteristics from long-term ponding test compared to other blends of fly ash. In BFS blends, an increase in compressive strength was observed only in the specimens of 25% BFS compared to other higher percentage blends, while the higher addition of 50 and 70% replacement showed no significant difference in compressive strength between them and their corresponding ternary blends with addition of silica fume. The results of this study indicate that control (OPC) specimens cast with increased w/b ratio of 0.48 showed higher chloride ingress compared to both binary blends of 70% fly ash and 70% BFS specimens. This indicates that (OPC) cast using higher w/b ratio is to be avoided in chloride environments. On the other hand, though, the ternary blends of 10% silica fume and up to 50% fly ash exhibited lower chloride ingress compared to their respective binary blends of fly ash. However, these ternary blends exhibited lower compressive strength, more negative corrosion potential and higher corrosion rate, compared to the respective binary blends of 25% fly ash and its ternary blends. Therefore, the recommended blend observed in the long-term ponding test is the ternary blend of 25% fly ash and 10% silica fume. The recommended level of corrosion resistance in slag specimens is achieved by the use of ternary blends comprising silica fume at 10% added to the blend that contains up to 70% slag. However, the recommended level of slag for a lower carbonation effect is the use of a ternary blend comprising 50% slag and 10% silica fume (3B5S1) which showed a carbonation depth of 10.8 mm and a compressive strength of 53.2 MPa after 365 days of exposure. The drying shrinkage of concrete increased with the increase in fly ash and the same trend was observed in BFS specimens. However, the results were not significantly different between their respective blends. The extent of carbonation in fly ash specimens was higher compared to BFS blends specimens. This can be attributed to the formation of dusty and weak surfaces on the outer surface in addition to the excessive leaching of sodium chloride solution from the long-term ponding test in the former specimens compared to later. The high volume pozzolanic materials, irrespective of fly ash or BFS and addition of silica fume (70% fly ash and 10% silica fume, and 70% BFS and 10% silica fume), showed higher cumulative pore volume indicating that these blends with seven days of curing were not beneficial. These high volume ternary blends required prolonged curing to release portlandite from the hydration of cement to continue the pozzolanic reaction. This study has shown that 7-days curing of the pozzolanic concrete is inadequate if pozzolanic activity is to be invoked. This is particularly the case when it is expected that the concrete is likely to be subjected to a harsher than usual environment characterised by a dry atmosphere.

The use of high performance concrete in construction has been enhanced by the use of pozzolanic materials. However, the use of these materials has not been optimized. Such optimization may be achieved by a systematic increase in the amount and combination of pozzolanic material additions, with accompanying studies of their effects on the mechanical, durability and microstructural characteristics of blended concrete. This work evaluated various concrete durability issues by studying systematic increases of pozzolanic materials such as fly ash and blast furnace slag (BFS) in the range of 25, 50 and 70%, and silica fume at 10% of total cementitious materials, forming various binary and ternary concrete blends. The concrete specimens were cured for a period of seven days after demoulding in line with widely practiced commercial curing procedures. The research explored the role and effectiveness of various binary and ternary blends of pozzolanic materials on the mechanical, durability and microstructural characteristics of concrete. Durability was evaluated by two independent rapid chloride permeability tests measured as charge passed and chloride conductivity from the RCPT and UCT tests respectively. These two rapid tests were coupled with long-term ponding tests to evaluate chloride ingress and the extent of corrosion for a period of two years. Further durability tests such as carbonation, drying shrinkage and porosity of these blends were also undertaken. This study also utilized micro-analytical techniques such as X-ray diffraction and Scanning Electron Microscopy to follow the hydration mechanism in various binary and ternary blends. Statistical significance testing was used to analyse and confirm all experimental results and conclusions. It is well known that a level of caution is exercised in the construction industry in the use of ternary blends. This study aims to evaluate the durability aspects of ternary concrete blends, in addition to binary blends, for resistance to chloride, corrosion, carbonation attacks and provide recommendations relating to the limits of blending level, as well as exposure conditions for blended concretes, based on the results of this study. It is expected that this will fill a major knowledge gap observed in the concrete industry. A comparison of two rapid chloride permeability tests such as UCT and RCPT indicates that the UCT test is easy and practicable, and does not contradict results obtained in the standard RCPT. However, the statistical significance of results obtained for some blends was only able to be established by using the RCPT. This effect can be attributed to the larger size specimens compared to UCT. The recommended blend to acquire both early-age and long-term strength development in fly ash is the ternary blends comprising 10% silica fume and 25% fly ash cast using lower w/b ratio. In addition, the same blend exhibited lower carbonation depth, lower charge passed from RCPT, lower chloride ingress and higher corrosion resistance characteristics from long-term ponding test compared to other blends of fly ash. In BFS blends, an increase in compressive strength was observed only in the specimens of 25% BFS compared to other higher percentage blends, while the higher addition of 50 and 70% replacement showed no significant difference in compressive strength between them and their corresponding ternary blends with addition of silica fume. The results of this study indicate that control (OPC) specimens cast with increased w/b ratio of 0.48 showed higher chloride ingress compared to both binary blends of 70% fly ash and 70% BFS specimens. This indicates that (OPC) cast using higher w/b ratio is to be avoided in chloride environments. On the other hand, though, the ternary blends of 10% silica fume and up to 50% fly ash exhibited lower chloride ingress compared to their respective binary blends of fly ash. However, these ternary blends exhibited lower compressive strength, more negative corrosion potential and higher corrosion rate, compared to the respective binary blends of 25% fly ash and its ternary blends. Therefore, the recommended blend observed in the long-term ponding test is the ternary blend of 25% fly ash and 10% silica fume. The recommended level of corrosion resistance in slag specimens is achieved by the use of ternary blends comprising silica fume at 10% added to the blend that contains up to 70% slag. However, the recommended level of slag for a lower carbonation effect is the use of a ternary blend comprising 50% slag and 10% silica fume (3B5S1) which showed a carbonation depth of 10.8 mm and a compressive strength of 53.2 MPa after 365 days of exposure. The drying shrinkage of concrete increased with the increase in fly ash and the same trend was observed in BFS specimens. However, the results were not significantly different between their respective blends. The extent of carbonation in fly ash specimens was higher compared to BFS blends specimens. This can be attributed to the formation of dusty and weak surfaces on the outer surface in addition to the excessive leaching of sodium chloride solution from the long-term ponding test in the former specimens compared to later. The high volume pozzolanic materials, irrespective of fly ash or BFS and addition of silica fume (70% fly ash and 10% silica fume, and 70% BFS and 10% silica fume), showed higher cumulative pore volume indicating that these blends with seven days of curing were not beneficial. These high volume ternary blends required prolonged curing to release portlandite from the hydration of cement to continue the pozzolanic reaction. This study has shown that 7-days curing of the pozzolanic concrete is inadequate if pozzolanic activity is to be invoked. This is particularly the case when it is expected that the concrete is likely to be subjected to a harsher than usual environment characterised by a dry atmosphere.

In Europe, clay roof tiles are manufactured by pressing in 'open' moulds whereas in South East Asia 'closed' moulds are commonly used. The European products are more complex, having a greater degree of detail. Closed mould pressing could, however, be advantageous as it would minimise scrap recycling but the products would need to have equivalent or superior durability to existing tiles. The aim of this work was to investigate the feasibility of using a closed mould for the manufacture of European tiles by examining the relationship between the type of pressing and subsequent durability, in terms of resistance to repetitive freeze-thaw cycles. One specific clay type, the Marseille rose blend, was investigated over a range of forming water contents. Preliminary data relating to plasticity and friction were obtained through an empirical (Pfefferkorn) plasticity test, uniaxial compression of cylinders and friction ring experiments. Clay cylinders containing 16-21 wt % water were deformed at a compression rate of 240 mm/min. The yield stress was found to increase with decreasing moisture content. The plastic ranges of the stress-strain curves were well represented by a plastic deformation equation of uniaxial compression under sticking friction conditions. A laboratory-scale pressing rig was designed to make profiled specimens which would reproduce the essential features of a European tile. Comparison of the microstructures of the laboratory and factory samples showed that there was sufficient resemblance to validate the replication of the Marseille products in the laboratory tests. Bats of three moisture contents of 16.4, 18.4 and 20.6 wt % and different geometries were pressed in open, partially closed and closed rubber lined resin moulds in a mechanical testing machine using a cross-head speed of 240 mm/min. This was lower than a typical pressing operation but the speed of pressing had been found to not be a significant variable over the range commonly encountered. Clay was trapped in the features as the mould closed and flowed mainly within the flat part of the samples during pressing. For the open and partially closed moulds excess material was extruded through the gaps at the sides, a process referred to as flashing. The shape of the load-displacement curves was characteristic of the stages of the pressing process. The stress-strain curves for the pressing in open moulds showed good qualitative agreement with the results from uniaxial compression of cylinders. The open porosity of the samples after firing was strongly related to the forming moisture content of the clay with the open porosity increasing with increasing water content. Comparison of extruded bats and pressed bars showed that the influence of the pressing processes was not significant. Likewise, in freeze-thaw testing, the effect of the moisture content was again the overriding parameter, with acceptable durability always being obtained from the lowest open porosity samples. Given the marginal differences, the pressing processes investigated in this study were assumed to be equivalent in terms of the quality of the samples produced. Thus, closed mould pressing is feasible but does not lead to product improvement and hence may not be economically viable.

Master of Science / Department of Civil Engineering / Asadollah Esmaeily / Reinforced concrete exceptional durability is a major reason why it is the most popular structural material in many infrastructures around the world. Most concrete structures serve for several decades; therefore problems of concrete durability gradually arise. To insure that concrete structures perform functionally, it is necessary to maintain and inspect them regularly. The durability of the reinforced concrete structures generally depends on four major factors: structure design and construction, maintenance, concrete aggregates, and environmental conditions. The most common causes of concrete deterioration are carbonation, design and construction errors, alkali-aggregate reactions, freeze-thaw cycles, and corrosion. Each type of concrete deterioration has its own signs and characteristics. Choosing the best repair technique to address concrete deterioration requires specific analysis and tests to find the cause of the deterioration and the extent of the damage. This study analyzes concrete structures inspection techniques to recognize the source of the problem and the part of the structure which has been affected. Choosing the most proper repair and strengthening techniques to prevent the structure from getting exposed to any further environmental and chemical are the next steps.

Ideally, asphalt pavements are designed to achieve sufficient stiffness prior to the application of traffic to resist rutting while also maintaining enough flexibility after years of service to minimize the amount of durability/brittleness related distresses (e.g. cracking and weathering). Multiple factors have caused an industry transition to mixes which are much more susceptible to crack, and durability related distresses are often the primary mechanism by which pavements fail. To restore a balance between rutting and durability distresses in asphalt pavements, the industry has started investigating balanced mix designs (BMDs). While mitigating only rutting or cracking behaviors is a straightforward exercise based on the collection of knowledge, simultaneously considering the two types of distresses is challenging considering that rutting is an early life distress and durability distresses are not typically observed until longer term aging has occurred. Mixture conditioning protocols to simulate field aging in conjunction with tests to fairly evaluate mixture integrity after conditioning are needed to scrutinize asphalt mixtures for durability related distresses during the mixture design phase. The current longer term conditioning protocol (R30) adopted by the American Association of State Highway and Transportation Officials (AASHTO) is not as severe as suggested when considering durability/brittleness (Isola et al. 2014; Yin et al. 2016; Cox et al. 2017). This dissertation’s primary objective is to provide guidance on asphalt mixture aging by contributing in four areas: 1) ensuring proper density measurement of field aged cores, 2) provide guidance on increased short term aging time effects in asphalt mixtures, 3) suggest improved mixture conditioning protocols to simulate longer term field aging, and 4) make suggestions for improving binder conditioning protocols to simulate longer term field aging. To these ends, a series of mixture and extracted binder tests were conducted on materials that were used to construct a full-scale test section in Columbus, MS that was monitored for aging for up to 5 after construction. The overall work presented provides simple recommendations or protocols which have the potential to improve the level of scrutiny that can be given to paving materials during the mix design phase and thus improve overall pavement performance.