Improvement of Fresh-State Concrete through Small Additions of Clay

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Title: Improvement of Fresh-State Concrete through Small Additions of Clay

Author(s): N. Tregger, R. Ferron, M. Beacraft, J. H. Kim, K. Kuder, and S. P. Shah

Publication: Special Publication

Volume: 270

Issue:

Appears on pages(s): 51-66

Keywords: clay; extrusion; formwork pressure; microstructure; self-consolidating concrete (SCC); slipform paving.

Date: 3/1/2010

Abstract:
Although clays such as metakaolin are typically incorporated into cement-based materials in order to improve hardened-state properties, recent findings at the Center for Advanced Cement-Based Materials (ACBM) have shown a large influence on the fresh-state. Furthermore, these benefits come at a much lower dosage, (~1% by mass of binder). A recent focus of ACBM has been the use of small dosages of clays in order to improve fresh-state properties such as extrudability and green strength. This paper summarizes several current projects at ACBM which demonstrate the effects of different commercial clays on relevant properties for three different scenarios: extrusion, formwork pressure of self-consolidating concrete (SCC) and slipform paving SCC. In each case, small additions of clays have shown marked improvements in the rheology of the cement composite. The use of two experimental methods to characterize the microstructural changes that occur with additions of clays is also reviewed.