Abstract
Fly ash (FA) is a promising industrial waste, which has been used in concrete technology as a cement replacement. However, its utilization is still limited compared to the quantity (approximately 36 million tons per year) of the FA being generated by ESKOM (the major South African electricity producer) as industrial waste. There is a need to improve the utilisation of the large amount of unused FA (approximately 94% of ash generated). The exploitation of the unique chemistry of FA is needed to make it more applicable in concrete, especially with a view to improving early strength and early durability development when it is used in concrete. This study aimed at investigating the effectiveness of using FA-cyclodextrin (an enzymatic modification of starch) composite, a novel composite, to beneficially modify concrete’s hydration products and hence increase FA usage in concrete technology.
Fly ash-cyclodextrin (FA-CD) composites were synthesized using two types of cyclodextrins (β and α) and two synthesis methods (physical mixtures and solution mixtures). The chemical structure and the microstructure of these composites were studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Scanning electron microscope (SEM). In these studies, the additional peaks in the X-ray diffractogram and IR-spectra of the composite materials indicated interaction between the cyclodextrins and FA. The change in the surface morphology, particle size and pore size, between the composite materials and constituent materials were also observed. Since the use of these composites are relatively new in concrete technology, compressive strength, split tensile strength, permeability, water sorptivity and porosity were determined on samples made using two composites synthesis methods with different percentages of β-cyclodextrin (0.1%, 0.2% and 0.5%) and 30% FA on concrete strengths (compressive and split tensile) and durability (permeability, sorptivity and porosity). Based on these tests results, further...
D.Ing.