Effect of pre-wetted perlite and fibers on autogenous and plastic shrinkage of high strength concrete

Autor: Ranjbar, Sahar
Jazyk: angličtina
Rok vydání: 2013
Druh dokumentu: Text
Popis: This thesis deals with the mitigation of plastic shrinkage in high strength concrete through internal curing and fiber reinforcement. In addition, the effects of mixture proportioning, internal curing and fiber reinforcement on elimination of autogenous shrinkage in mortar were studied. Internal curing can prevent cement paste from self-desiccation by providing small water reservoirs within the mortar or concrete. Fiber reinforcement can potentially increase the early age tensile strength. Plastic shrinkage cracks were observed only on the control concrete specimens. That is, the addition of fibers and partial replacement of fines with pre-wetted perlite both provided viable mechanisms to mitigate or reduce plastic shrinkage in high strength concrete. The fibers had a negligible effect on compressive strength. However, there was a significant decrease in compressive strength for mixes containing 25% perlite by volume of fine aggregate. Based on these results, 0.15% fibers by volume appears to be more useful than 25% perlite by volume for mitigating plastic shrinkage in high strength concrete. The mixes without pre-wetted perlite underwent autogenous shrinkage; while the internally cured mixes underwent some swelling. That is, partial replacement of fines with pre-wetted perlite provided viable mechanism to completely eliminate autogenous shrinkage in high strength mortar. The mortar mix with fly ash exhibited the least amount of autogenous shrinkage. Therefore, in cases where addition of pre-wetted perlite is not desirable due to the loss in mechanical properties, sacrifices, fly ash can be considered as a good replacement for internal curing agent.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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