Self-Compacting High-Performance Concretes

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Title: Self-Compacting High-Performance Concretes

Author(s): Mario Collepardi, Roberto Troli, and Stefano Maringoni

Publication: Special Publication

Volume: 289

Issue:

Appears on pages(s): 1-7

Keywords: Crack-freedom. Drying shrinkage. Expansive agent. Self-compacting concrete. Shrinkage-reducing admixture. Superplasticizer.

Date: 9/14/2012

Abstract:
Self-compacting high-performance concretes have been manufactured by mixing natural aggregates, portland cement and ground limestone filler in the presence of a poly-carboxylate superplasticizer. In some concrete mixtures a shrinkage-reducing admixture (SRA) was used to decrease the drying shrinkage by 30% with respect to the control mix without SRA when the specimens were kept at room temperature with a relative humidity (RH) permanently kept as low as 55%. A special SCC was manufactured combining a CaO-based expansive agent with SRA and the restrained expansion was measured in the absence of any wet curing in very dry environment (RH = 50%). After 2-3 months the restrained expansion was lost but no crack was recorded although the RH was very low. Similar results were obtained by using a combination of PVA macrofibres with SRA: no reduction in drying shrinkage was recorded in the PVA-SRA concrete with respect to the SRA concrete. However, in the presence of PVA both the number and the thickness of the cracks were significantly reduced. The combined uses of SRA with the expansive agent or the macrofibres make more reliable concretes from the durability point of view because of the absence of cracks.