Effects of the Fineness of Fly Ash on the Flow and Compressive Strength of Portland Cement Mortars


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Title: Effects of the Fineness of Fly Ash on the Flow and Compressive Strength of Portland Cement Mortars

Author(s): Sandor Popovics

Publication: Special Publication

Volume: 141


Appears on pages(s): 205-226

Keywords: compressive strength; fly ash; mortars (material); silica fume; strength; superplasticizer; velocity; Materials Research

Date: 12/1/1993

Results of a laboratory test series are reported concerning the effect of cement type, class of fly ash, and fineness of fly ash on the strength development of mortars. Thirty percent by weight of portland cement was substituted by fly ash. The following materials were used in various combinations: Type I and Type III portland cements, Class F fly ash before and after grinding, Class C fly ash before and after grinding, a silica fume, a superplasticizer, and an accelerating admixture. More than 60 different compositions were tested in all. Standard flow, compressive strength, and pulse velocity measurements were performed in the standard manner at 1, 7, and 28 days. The obtained results show the effects of fineness of fly ash, along with other characteristics of mortar composition, on the flow and strength development, as well as the interactions between fineness and cement type. For instance, as expected, ground Class F fly ash with Type I cement produced lower strengths at 1 day than the same fly ash with its original fineness and Type III cement; however, at 7 and 28 days, the fly ash mortars with Type I cement showed higher strengths. The results of the pulse velocity tests showed the same trend as the strength results.