The Influence of Superplasticizer on Mixture Proportioning and the Strength and Durability of Silica Fume Concrete

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Title: The Influence of Superplasticizer on Mixture Proportioning and the Strength and Durability of Silica Fume Concrete

Author(s): S.A. Austin and PJ. Robins

Publication: Special Publication

Volume: 148

Issue:

Appears on pages(s): 259-280

Keywords: Climate; compressive strength; curing; durability; mix proportioning; permeability; porosity; silica fume; superplasticizers; workability

Date: 9/1/1994

Abstract:
This paper reports on part of a substantial research programme on properties of condensed silica fume (CSF) concretes cured in temperate and climates, carried out in the Department of Civil Engineering at Loughborough. The hot The research approach was to investigate mixtures proportioned to have equal workability and 28 day strength (when water cured at 20°C). This paper examines the effect of superplastizer, curing method (water and polythene) and curing environment (temperate and hot) on the compressive strength, permeability and pore structure of 40 MPa concretes. More specifically, the paper contrasts the performance of two 15% CSF mixtures (replacement by weight of cement) where workabilities were controlled by the addition of extra water or superplasticizer. The development of the concretes’ strength and subsurface permeability index (air and water) with age (from 7 to 180 days) is described, together with the intrinsic permeability (air and water) and pore structure of their equivalent mortar fraction. The use of superplasticizer to control workability increased the compressive strength of CSF concrete mixtures by around 18% and 10% in the temperate and hot environments respectively. The super-plasticized concrete had lower air and water permeabilities which is attributed to an improved pore structure as confirmed by mercury intrusion porosimetry date. The improvements were more marked in the CSF concretes cured in a hot environment.