Development of fly ash-based composite binder and its application in construction materials

Abstract

The effect of addition of metakaolin on hydration and physico-chemical properties of fly ash composite binder prepared by blending 50–60% fly ash with hydrated lime sludge, Portland cement and gypsum plaster were investigated. The metakaolin has a beneficial effect on the properties of composite binder by reducing its porosity and pore diameter with curing period which are responsible for the attainment of high strength and better stability towards water over the composite binder without metakaolin. The strength development in composite binder takes place due to the hydration of gypsum plaster to gypsum and pozzolanic reaction of fly ash, metakaolin with lime and alkali in cement thereby forming ettringite, tobermorite and C₄AH₁₃. The reaction products formed during the hydration were confirmed by X-ray diffraction, differential thermal analysis and scanning electron microscopy. The composite binder has low heat of hydration and is found suitable for use in masonry works, concrete and bricks.

Keywords:

• metakaolin
• fly ash
• hydration
• compressive strength
• porosity

Acknowledgement

The work reported in this paper forms a part of the normal research programme at the CSIR-Central Building Research Institute, Roorkee (India). The authors are grateful to Prof. S.K. Bhattacharyya, Director, Central Building Research Institute, Roorkee for giving the permission for publication of the paper.