Fly Ash Customization for Defined Performance Concretes


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Title: Fly Ash Customization for Defined Performance Concretes

Author(s): H.A.W. Cornelissen and J.W. van den Berg

Publication: Special Publication

Volume: 178


Appears on pages(s): 239-256

Keywords: fineness; fly ash; high-performance concrete; self compacting concrete; silica fume; workability.

Date: 6/1/1998

This paper describes the approach for customization of fly ash, focused on the proportioning of concrete mixtures for applications where specific performance is needed such as strength, durability and workabili-ty. In order to tailor these specific concrete mixtures, bulk fly ashes can be selected and upgraded to fulfil the requirements with respect to for instance, grain size distribution and carbon content (LOI). By customizati-on of fly ash its value will increase, which is beneficial inspite of the cost for upgrading. For customization, basic knowledge and relationships are needed about the decisive influential factors of the total system of concre-te components and design. To this end, descriptive models have been evaluated and applied with the emphasis on models for fly ash fineness and packing. These models have been used as a background for classifica-tion and micronization of fly ash. In experimental work, a relation was found between the dry pac-king of the solid constituents of mortar and the workability after the addition of water. Then fine and ultra-fine fly ashes were processed throu-gh air-classification and grinding (micronization). These processed fly ashes were added to concrete and the strength development was compared to concrete with silica fume and with reference concrete. In full scale tests the suitability of micronized fly ash for the production of very workable concrete, was confirmed.