Upgrading of PFA for Utilization in Concrete

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Title: Upgrading of PFA for Utilization in Concrete

Author(s): H. A. W. Cornelissena and C. H. Gast

Publication: Special Publication

Volume: 132

Issue:

Appears on pages(s): 457-470

Keywords: aggregate gradation; air classification; concretes; fineness; fly ash; mortars (material); packing; PFA; thermal conductivity (K-factor); water-cement ratio; Materials Research

Date: 5/1/1992

Abstract:
To remove coarse PFA particles from bulk fly ash batches, a pilot plant air classifier was built and tested. This plant also enabled the production of fly ash gradings with various particle size distributions. The effect of upgrading by air classification on mortar and concrete properties was investigated in an extended research program. For that purpose, the PFA particle size distribution was expressed by the grading modulus, which proved to correlate well with fresh mortar and fresh concrete properties, as well as with strength and efficiency factors of the hardened materials. A simplified model for packing the dry components (fly ash, cement, and sand) of mortar was derived and applied. For the combinations investigated, mixes with coarser sized cement showed the highest packing density. A dense packing proved to be favorable for fresh mortar and hardened mortar properties.