The influence of fly ash and ground granulated blastfurnace slag on restrained shrinkage cracking of bonded overlays
Master Thesis
2016
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University of Cape Town
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The concrete repair industry is driven by deterioration of, damage to, and defects in concrete structures. The impact of deterioration or damage is a reduction in the service life of the concrete structure. One of the common methods used to repair and rehabilitate damaged concrete structures is the bonded overlay technique. However, bonded overlays are prone to restrained shrinkage cracking which impairs their performance. The mechanism leading to restrained shrinkage cracking of bonded concrete overlays is complex and depends on material properties, such as shrinkage, tensile strength, elastic modulus, and tensile relaxation. In order to reduce the risk of cracking in bonded concrete overlays, one or a combination of the following is required: lower shrinkage strains, higher tensile strength, lower elastic modulus, and increased stress relaxation. The development of these material properties depends on the degree of hydration of the binder material. Fly ash (FA) and slag (GGBS) are known to influence the hydration reaction when added to the binder material. This change in hydration reactions affects the development of the mechanical properties of the concrete, which ultimately affects the outcome of restrained shrinkage. An increase in age at cracking with the use of fly ash and slag in bonded concrete overlays was hypothesised. The research aimed at investigating the influence of fly ash and slag on the performance of bonded concrete overlays with regards to restrained shrinkage cracking. The research also aimed at using the influence of fly ash and slag on the specific material properties governing restrained shrinkage to analyse and predict the performance of the overlay materials
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Chibulu, C. 2016. The influence of fly ash and ground granulated blastfurnace slag on restrained shrinkage cracking of bonded overlays. University of Cape Town.