Reinforced Alkali-Activated Concrete (AAC) and Bond Properties
Mladena Lukovic (TU Delft - Concrete Structures)
Zhenxu Qian (TU Delft - Concrete Structures)
Jelle Bezemer (TU Delft - Concrete Structures)
Arkamitra Kar (Birla Institute of Technology and Science, Pilani)
Choi Lin Chan (University College London)
Mingzhong Zhang (University College London)
Frank Dehn (Karlsruhe Institut für Technologie)
Guang Ye (TU Delft - Materials and Environment)
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Abstract
The increasing demand for sustainable development in engineering practice has triggered researchers to explore solutions to reduce the CO2 footprint caused by Portland cement (PC) production. Alkali-activated concrete (AAC), made by alkali activation of industrial by-products, poses to be a sustainable alternative to traditional Portland cement concrete. Despite vast studies on its material properties, there is still insufficient knowledge on the structural performance of reinforced AAC members, which impedes its widespread application. Bond between concrete and embedded reinforcement is critical for the structural behaviour of reinforced members, including crack propagation (crack opening and crack spacing), load carrying capacity, deformational capacity and seismic resistance. In this chapter, a critical review on the bond behaviour between AAC and reinforcement is given. A vast variety of tests have been used for studying the AAC-reinforcement bond. Similar to traditional PC concrete, different setup configurations and specimen geometries affect not only the measured bond strength, but also the nature of the bond response. Therefore, in this review different bond tests are discussed, focusing on application of both conventional steel and fibre reinforced polymer (FRP) as reinforcement. Given that AAC is a wide class of materials with largely varying mechanical properties, this study systematically classifies bond results based on different types of precursors used. Furthermore, numerical methods to predict AAC flexural response as well as the applicability of existing PC concrete design codes are summarized. It is concluded that AAC beams show comparable short-term bond behaviour with traditional PC concrete of the same strength class. Although the design codes for traditional concrete turn out to be usually applicable for the AAC-reinforcement bond, opposite trends were also reported. Finally, whereas the short-term behaviour has been widely investigated for AAC bond, systematic studies dealing with its long-term behaviour are lacking. Time dependent effects must be considered when developing reliable guidelines and recommendations for future structural design of AAC.