00637529

Monograph

http://onlinepubs.trb.org...nepubs/shrp/SHRP-C-629.pdf

This report describes research into the nature of the interfacial region in concrete. The interfacial region, considered more porous than the paste itself, could act both as a localized 'weakness' where fractures are initiated, and as an avenue of attack for aggressive chemical agents. Computer simulations of particle packing against an aggregate surface show that it is the efficency by which particles pack against the aggregate during mixing which influences the nature and strength of the interfacial region which develops over time. Also, simulation results suggest that the degree of flocculation and the intensity of mixing are not entirely independent variables. The study confirmed the belief that mortars contain zones of enhanced interfacial porosity. Mixes made with Class C fly ash were the only exceptions where interfacial porosity was nearly non-existent. Data also suggests that air permeability may be directly related the presence of larger pores - 200 nm (200A) rather than the smaller paste pores -20 nm (200 A). Finally, it was observed that differnces in interfacial and paste porosites became less significant at longer curing times.

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SHRP-C-629

English

76 p.

1993-5

Figures; Tables

Aggregates; Cement paste; Concrete curing; Interfaces; Microstructure; Permeability; Porosity

Geotechnology; Highways; Materials; I32: Concrete

TRIS, TRB, ATRI

Oct 1 1993 12:00AM