Factors Affecting the Autogenous Shrinkage of Ground Granulated Blast-Furnace Slag Cement Concrete

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Title: Factors Affecting the Autogenous Shrinkage of Ground Granulated Blast-Furnace Slag Cement Concrete

Author(s): J. M. Aldred and S. N. Lee

Publication: Special Publication

Volume: 221

Issue:

Appears on pages(s): 783-796

Keywords: autogenous shrinkage; capillary pore pressure; dessication; ground granulated blast-furnace slag; pore size distribution

Date: 5/1/2004

Abstract:
The influence of ground granulated blast-furnace (GGBF) slag on autogenous shrinkage in concrete with a water/cementitious material (w/cm) of 0.3 and 91-day strength in excess of 80 MPa was investigated under tropical conditions. Cement re-placement percentages of 30, 50, 65 and 80% by GGBF slag were examined as well as the finenesses of 4200, 6000 and 7900 cm2/g for the 65% replacement percentage. The GGBF slag increased significantly the cumulative autogenous shrinkage for all replacement percentages and fineness levels tested. The increased autogenous strain occurred within the first 14 days when hydration would have been dominated by the portland cement component, well before significant additional hydration or pore refinement would have been possible due to hydration of the GGBF slag component. This suggests that the driving force for autogenous shrinkage in GGBF slag concrete may differ fundamentally from that for portland cement and silica fume concrete. Possible mechanisms for the increased early autogenous shrinkage in GGBF slag concrete are discussed.