Enhancing High Volume Fly Ash Concretes Using Fine Limestone Powder

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Title: Enhancing High Volume Fly Ash Concretes Using Fine Limestone Powder

Author(s): Jussara Tanesi, Dale Bentz, and Ahmad Ardani

Publication: Special Publication

Volume: 294

Issue:

Appears on pages(s): 1-14

Keywords: Constructability; fine limestone powder; high volume fly ash concrete; setting; sustainability.

Date: 10/4/2013

Abstract:
One of the primary approaches to producing more sustainable concretes consists of replacing 50 % or more of the portland cement in a conventional concrete with fly ash, producing a so-called high volume fly ash (HVFA) concrete. While these mixtures typically perform admirably in the long term, they sometimes suffer from early-age performance issues including binder/admixture incompatibilities, delayed setting times, low early-age strengths, and a heightened sensitivity to curing conditions. Recent investigations have indicated that the replacement of a portion of the fly ash in these concrete mixtures by a suitably fine limestone powder can mitigate these early-age problems. The current study investigates the production of concrete mixtures where either 40 % or 60 % of the portland cement is replaced by fly ash (Class C or Class F) and limestone powder, on a volumetric basis. The mixtures are characterized based on measurement of their fresh properties, heat release, setting times, strength development, rapid chloride penetrability metrics and surface resistivity. The limestone powder not only accelerates the early age reactions of the cement and fly ash, but also provides significant benefits at ages of 28 d and beyond for both mechanical and transport properties.