Durability design strategies for new cementitious materials

2013 ◽  
Vol 54 ◽  
pp. 114-125 ◽  
Author(s):  
Frank Altmann ◽  
Viktor Mechtcherine
Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4437
Author(s):  
Shashank Gupta ◽  
Salam Al-Obaidi ◽  
Liberato Ferrara

Concrete and cement-based materials inherently possess an autogenous self-healing capacity. Despite the huge amount of literature on the topic, self-healing concepts still fail to consistently enter design strategies able to effectively quantify their benefits on structural performance. This study aims to develop quantitative relationships through statistical models and artificial neural network (ANN) by establishing a correlation between the mix proportions, exposure type and time, and width of the initial crack against suitably defined self-healing indices (SHI), quantifying the recovery of material performance. Furthermore, it is intended to pave the way towards consistent incorporation of self-healing concepts into durability-based design approaches for reinforced concrete structures, aimed at quantifying, with reliable confidence, the benefits in terms of slower degradation of the structural performance and extension of the service lifespan. It has been observed that the exposure type, crack width and presence of healing stimulators such as crystalline admixtures has the most significant effect on enhancing SHI and hence self-healing efficiency. However, other parameters, such as the amount of fibers and Supplementary Cementitious Materials have less impact on the autogenous self-healing. The study proposes, through suitably built design charts and ANN analysis, a straightforward input–output model to quickly predict and evaluate, and hence “design”, the self-healing efficiency of cement-based materials.


Author(s):  
Jonathan G. M. Wood

In the 1980s engineers faced major challenges from severe concrete deterioration from AAR (Alkali Aggregate Reaction) and from corrosion. The construction of the Channel and Storebaelt Tunnels required major improvements in specifying concrete to combat both these problems. Anglo-Danish cooperation of consultants and research centres led to innovations in cementitious materials, assessment of aggregates, the testing of materials and predicting deterioration. Since then RILEM has provided an international framework to guide developments on AAR diagnosis, appraisal, testing and specification. Quantitative durability design remains in its infancy. Rapid testing data do not predict migration over many decades. Fick’s law models neglect the physical and chemical processes of chloride migration. Data from old structures is needed for calibrating models and validating theories.


Author(s):  
F. J. Cunha ◽  
W. Abdel-Messeh ◽  
M. K. Chyu

Aircraft propulsion engines, land-based power generation, and industrial machines have, as a primary component, the turbine as means to produce thrust or generate power. In the turbine section of the engine, airfoil components are subjected to extremely complex and damaging environments. The combination of high gas temperatures and pressures, strong gradients, abrupt geometry changes, viscous forces, rotational forces, and unsteady turbine vane/blade interactions, all combine to offer a formidable challenge in terms of turbine durability. Nevertheless, the ultimate goal is to maintain or even improve the highest level of turbine performance and simultaneously reduce the amount of cooling flow needed to achieve this end. As such, coolant flow is a penalty to the cycle and thermal efficiency. Cooling strategies are developed and presented to determine ways for coolant flow management. The main variables include film cooling configurations, and convective efficiency schemes to balance turbine airfoil thermal loads for target overall cooling effectiveness. The desired targets are determined by the turbine airfoil durability requirements of oxidation and fatigue on a local scale and for creep on the bulk scale. Emphasis is provided to the general modes of cooling including film cooling, impingement cooling, and convective cooling for different parts of the airfoil such as leading edge, mid-body, trailing edge, tip and endwalls. Convective cooling is presented in terms of fundamental cooling enhancements, such as turbulating trip strips and pedestals. Recent literature dealing with these topics is listed.


10.1617/14020 ◽  
2003 ◽  
Vol 36 (257) ◽  
pp. 191-196 ◽  
Author(s):  
G. Constantinides

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