Superplasticizers and Concrete Durability

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Title: Superplasticizers and Concrete Durability

Author(s): R. N. Swamy

Publication: Special Publication

Volume: 119

Issue:

Appears on pages(s): 361-382

Keywords: carbonation; compressive strength; concrete durability; high-strength concretes; microstructures; mix proportioning; mortars (material); permeability; plasticizers; strength; workability; Materials Research

Date: 9/1/1989

Abstract:
Concrete durability has become a matter of great practical significance. It is particularly critical to reinforced and prestressed structures where lack of concrete durability can lead to lack of structural stability and integrity through steel corrosion. The two significant factors affecting and controlling concrete durability are permeability and porosity. While nonadmixture low w/c concrete can be durable, this paper puts forward the thesis that it is superplasticizers that can insure long-term durability of concrete and concrete structures. For too long, water-reducing agents, plasticizers, and superplasticizers have been looked upon as workability/pumping agents with possible savings in cement and increases in compressive strength. It is suggested that this concept of these admixtures is misleading and ill-informed. While good workability is recognized as an essential component of placing and compacting, the more critical role of superplasticizers should be seen to reduce the porosity and sorptivity of concrete through water reduction. Paper presents test data on concrete and mortar mixes with blended cements and superplasticizers and having water-binder ratios of 0.35 to 0.40. The properties of these concretes are presented and discussed in terms of strength development, permeability, pore structure, carbonation, and microstructure. It is shown that superplasticizers should be seen as agents of concrete durability rather than as agents of concrete workability.