Abstract
The focus of this research is to modify fly ash (FA) structure using β - cyclodextrin (β-CD) to increase its pozzolanic function in concrete. A previous study by the authors has shown that a composite is formed due to structural changes of fly ash by its interaction with cyclodextrin [1]. The objective of this paper was to assess the effect of fly ash-β cyclodextrin composite (FA-β-CD) on the transport properties (durability performance) of mortar and concrete, with a view to optimise its incorporation in concrete. The durability performance of mortar and concrete were assessed from the measurement of oxygen gas
permeability, sorptivity and porosity using the South Africa durability index approach. Six mixtures were tested, comprising a control mixture (100% Portland Cement, PC), and five mixes containing the FA-β CD composite. All the composite mixes included 30 % FA by mass. The β-CD was mixed with the FA, in separate mixtures, in proportions of 0.1 %, 0.2 % and 0.5 %. Two sample preparation procedures were followed for FA-β-CD composites mixtures; firstly, physical mixtures of a pre-weighed amount of β-CD and FA were adopted for the dry mixtures and secondly, 0.0103M, 0.0206M and 0.0516Mβ-CD solutions were
added to the concrete at the mixing stage for solution mixtures. The results indicated that FA-β-CD composite improved the flowability and durability performances when β-cyclodextrin (β-CD) was used at a lower percentage (0.1% and 0.2%).