AA
A. Abbasi
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Alkali-Silica Reaction (ASR) poses a significant challenge to the durability and structural integrity of reinforced concrete structures worldwide. This thesis presents a comprehensive modelling framework that integrates numerical simulations and phenomenological models to predict the long-term behaviour of ASR-affected structures. The framework addresses the progressive degradation of material properties and the structural implications of ASR-induced expansion, using expansion characteristics derived from experimental data.
Several numerical methods exist to simulate ASR effects at the structural scale. Among these, the Dual Mesh Method (DMM) stands out as novel pre-damage method to simulate ASR induced damage in reinforced concrete. Building upon this approach, this research develops the Modified Dual Mesh Method (MDMM), introducing key advancements such as an adapted tensile curve (ATC) to enhance its predictive capabilities.
The MDMM was validated numerically against reinforced concrete beam behaviour, demonstrating its effectiveness in simulating ASR-induced stress generation, crack propagation, and material degradation under incremental expansion conditions. A comparative analysis with the Reduced Material Properties Method (RMPM) highlighted the MDMM's effective ability to account for internal expansion forces and anisotropic behaviour influenced by structural configurations. The results confirmed the framework's accuracy in replicating critical structural responses such as crack propagation patterns and load-deflection behaviour.
Phenomenological models by Larive and Esposito were integrated into the framework, linking ASR-induced expansion with time and material property degradation. These models enabled long-term damage simulations and were applied to a hypothetical bridge pier cap. The simulation successfully captured key aspects of ASR-induced damage, including crack alignment with reinforcement, stress redistribution, and reinforcement yielding, providing insights into the service life thresholds of ASR-affected structures.
While the framework demonstrates promising capabilities, it remains in an early development stage. Limitations were observed, particularly in accurately representing the gradual reduction of elastic modulus associated with ASR progression. Further validation with complete case studies and exploration of diverse structural configurations are recommended to enhance its applicability and reliability.
This research offers a valuable tool for structural assessment, maintenance planning of ASR-affected infrastructure, bridging the gap between experimental observations and predictive modelling of long-term structural performance.
...
Several numerical methods exist to simulate ASR effects at the structural scale. Among these, the Dual Mesh Method (DMM) stands out as novel pre-damage method to simulate ASR induced damage in reinforced concrete. Building upon this approach, this research develops the Modified Dual Mesh Method (MDMM), introducing key advancements such as an adapted tensile curve (ATC) to enhance its predictive capabilities.
The MDMM was validated numerically against reinforced concrete beam behaviour, demonstrating its effectiveness in simulating ASR-induced stress generation, crack propagation, and material degradation under incremental expansion conditions. A comparative analysis with the Reduced Material Properties Method (RMPM) highlighted the MDMM's effective ability to account for internal expansion forces and anisotropic behaviour influenced by structural configurations. The results confirmed the framework's accuracy in replicating critical structural responses such as crack propagation patterns and load-deflection behaviour.
Phenomenological models by Larive and Esposito were integrated into the framework, linking ASR-induced expansion with time and material property degradation. These models enabled long-term damage simulations and were applied to a hypothetical bridge pier cap. The simulation successfully captured key aspects of ASR-induced damage, including crack alignment with reinforcement, stress redistribution, and reinforcement yielding, providing insights into the service life thresholds of ASR-affected structures.
While the framework demonstrates promising capabilities, it remains in an early development stage. Limitations were observed, particularly in accurately representing the gradual reduction of elastic modulus associated with ASR progression. Further validation with complete case studies and exploration of diverse structural configurations are recommended to enhance its applicability and reliability.
This research offers a valuable tool for structural assessment, maintenance planning of ASR-affected infrastructure, bridging the gap between experimental observations and predictive modelling of long-term structural performance.
...
Alkali-Silica Reaction (ASR) poses a significant challenge to the durability and structural integrity of reinforced concrete structures worldwide. This thesis presents a comprehensive modelling framework that integrates numerical simulations and phenomenological models to predict the long-term behaviour of ASR-affected structures. The framework addresses the progressive degradation of material properties and the structural implications of ASR-induced expansion, using expansion characteristics derived from experimental data.
Several numerical methods exist to simulate ASR effects at the structural scale. Among these, the Dual Mesh Method (DMM) stands out as novel pre-damage method to simulate ASR induced damage in reinforced concrete. Building upon this approach, this research develops the Modified Dual Mesh Method (MDMM), introducing key advancements such as an adapted tensile curve (ATC) to enhance its predictive capabilities.
The MDMM was validated numerically against reinforced concrete beam behaviour, demonstrating its effectiveness in simulating ASR-induced stress generation, crack propagation, and material degradation under incremental expansion conditions. A comparative analysis with the Reduced Material Properties Method (RMPM) highlighted the MDMM's effective ability to account for internal expansion forces and anisotropic behaviour influenced by structural configurations. The results confirmed the framework's accuracy in replicating critical structural responses such as crack propagation patterns and load-deflection behaviour.
Phenomenological models by Larive and Esposito were integrated into the framework, linking ASR-induced expansion with time and material property degradation. These models enabled long-term damage simulations and were applied to a hypothetical bridge pier cap. The simulation successfully captured key aspects of ASR-induced damage, including crack alignment with reinforcement, stress redistribution, and reinforcement yielding, providing insights into the service life thresholds of ASR-affected structures.
While the framework demonstrates promising capabilities, it remains in an early development stage. Limitations were observed, particularly in accurately representing the gradual reduction of elastic modulus associated with ASR progression. Further validation with complete case studies and exploration of diverse structural configurations are recommended to enhance its applicability and reliability.
This research offers a valuable tool for structural assessment, maintenance planning of ASR-affected infrastructure, bridging the gap between experimental observations and predictive modelling of long-term structural performance.
Several numerical methods exist to simulate ASR effects at the structural scale. Among these, the Dual Mesh Method (DMM) stands out as novel pre-damage method to simulate ASR induced damage in reinforced concrete. Building upon this approach, this research develops the Modified Dual Mesh Method (MDMM), introducing key advancements such as an adapted tensile curve (ATC) to enhance its predictive capabilities.
The MDMM was validated numerically against reinforced concrete beam behaviour, demonstrating its effectiveness in simulating ASR-induced stress generation, crack propagation, and material degradation under incremental expansion conditions. A comparative analysis with the Reduced Material Properties Method (RMPM) highlighted the MDMM's effective ability to account for internal expansion forces and anisotropic behaviour influenced by structural configurations. The results confirmed the framework's accuracy in replicating critical structural responses such as crack propagation patterns and load-deflection behaviour.
Phenomenological models by Larive and Esposito were integrated into the framework, linking ASR-induced expansion with time and material property degradation. These models enabled long-term damage simulations and were applied to a hypothetical bridge pier cap. The simulation successfully captured key aspects of ASR-induced damage, including crack alignment with reinforcement, stress redistribution, and reinforcement yielding, providing insights into the service life thresholds of ASR-affected structures.
While the framework demonstrates promising capabilities, it remains in an early development stage. Limitations were observed, particularly in accurately representing the gradual reduction of elastic modulus associated with ASR progression. Further validation with complete case studies and exploration of diverse structural configurations are recommended to enhance its applicability and reliability.
This research offers a valuable tool for structural assessment, maintenance planning of ASR-affected infrastructure, bridging the gap between experimental observations and predictive modelling of long-term structural performance.
Drying shrinkage of alkali-activated concrete -State-of-the-art
A research study into the mechanisms, the influencing factors, and mitigation strategies of drying shrinkage of alkali-activated concrete
Alkali-activated concrete (AAC) has emerged as an environmentally friendly alternative to conventional concrete, as It is a cement-free concrete made by activating precursors (mainly low-cost, low-CO2 industrial by-products) with alkalis. AAC has demonstrated some remarkable mechanical properties and long-term performance (e.g., high strength, chemical durability, and fire resistance). However, high drying shrinkage in AAC, causing cracks degrading the long-term durability of AAC, is one of the obstacles that must be overcome before it can be widely applied in the construction field.
This study investigates the mechanisms of drying shrinkage, provides a survey and evaluation of the influencing factors, and accordingly proposes an integral solution to mitigate drying shrinkage in AAC. This was done through a qualitative approach based on literary research.
The investigation showed that the main driving forces of drying shrinkage are surface, disjoining, and capillary tension forces, and they are related to relative humidity (RH) and meniscus radius. Further, different reaction products' characteristics can be attributed to different drying shrinkage mechanisms, as they have a critical role in determining AAC properties. Furthermore, poor mechanical properties of AAC often lead to a higher drying shrinkage rate. Surveying the influencing factors of drying shrinkage of AAC, in terms of raw materials, mix designs, and curing conditions showed their significant effect on drying shrinkage magnitude and mechanical properties. These factors were accordingly evaluated and systematized. Therefore, based on the survey and evaluation, a strategy was proposed to mitigate drying shrinkage in AAC. ...
This study investigates the mechanisms of drying shrinkage, provides a survey and evaluation of the influencing factors, and accordingly proposes an integral solution to mitigate drying shrinkage in AAC. This was done through a qualitative approach based on literary research.
The investigation showed that the main driving forces of drying shrinkage are surface, disjoining, and capillary tension forces, and they are related to relative humidity (RH) and meniscus radius. Further, different reaction products' characteristics can be attributed to different drying shrinkage mechanisms, as they have a critical role in determining AAC properties. Furthermore, poor mechanical properties of AAC often lead to a higher drying shrinkage rate. Surveying the influencing factors of drying shrinkage of AAC, in terms of raw materials, mix designs, and curing conditions showed their significant effect on drying shrinkage magnitude and mechanical properties. These factors were accordingly evaluated and systematized. Therefore, based on the survey and evaluation, a strategy was proposed to mitigate drying shrinkage in AAC. ...
Alkali-activated concrete (AAC) has emerged as an environmentally friendly alternative to conventional concrete, as It is a cement-free concrete made by activating precursors (mainly low-cost, low-CO2 industrial by-products) with alkalis. AAC has demonstrated some remarkable mechanical properties and long-term performance (e.g., high strength, chemical durability, and fire resistance). However, high drying shrinkage in AAC, causing cracks degrading the long-term durability of AAC, is one of the obstacles that must be overcome before it can be widely applied in the construction field.
This study investigates the mechanisms of drying shrinkage, provides a survey and evaluation of the influencing factors, and accordingly proposes an integral solution to mitigate drying shrinkage in AAC. This was done through a qualitative approach based on literary research.
The investigation showed that the main driving forces of drying shrinkage are surface, disjoining, and capillary tension forces, and they are related to relative humidity (RH) and meniscus radius. Further, different reaction products' characteristics can be attributed to different drying shrinkage mechanisms, as they have a critical role in determining AAC properties. Furthermore, poor mechanical properties of AAC often lead to a higher drying shrinkage rate. Surveying the influencing factors of drying shrinkage of AAC, in terms of raw materials, mix designs, and curing conditions showed their significant effect on drying shrinkage magnitude and mechanical properties. These factors were accordingly evaluated and systematized. Therefore, based on the survey and evaluation, a strategy was proposed to mitigate drying shrinkage in AAC.
This study investigates the mechanisms of drying shrinkage, provides a survey and evaluation of the influencing factors, and accordingly proposes an integral solution to mitigate drying shrinkage in AAC. This was done through a qualitative approach based on literary research.
The investigation showed that the main driving forces of drying shrinkage are surface, disjoining, and capillary tension forces, and they are related to relative humidity (RH) and meniscus radius. Further, different reaction products' characteristics can be attributed to different drying shrinkage mechanisms, as they have a critical role in determining AAC properties. Furthermore, poor mechanical properties of AAC often lead to a higher drying shrinkage rate. Surveying the influencing factors of drying shrinkage of AAC, in terms of raw materials, mix designs, and curing conditions showed their significant effect on drying shrinkage magnitude and mechanical properties. These factors were accordingly evaluated and systematized. Therefore, based on the survey and evaluation, a strategy was proposed to mitigate drying shrinkage in AAC.