Air-Void Characteristics and Freezing and Thawing Resistance of Superplasticized Air-Entrained Concrete With High Workability

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Title: Air-Void Characteristics and Freezing and Thawing Resistance of Superplasticized Air-Entrained Concrete With High Workability

Author(s): E. Siebel

Publication: Special Publication

Volume: 119

Issue:

Appears on pages(s): 297-320

Keywords: admixtures; air-entrained concretes; air-entraining agents; freeze-thaw durability; microscopy; plasticizers; workability; Materials Research

Date: 9/1/1989

Abstract:
Conflicting information on the freeze-thaw resistance of superplasticized concrete is given in the literature. For this reason, the Research Centre of the German Cement Industry instigated an extensive research program. Superplasticizers based on melamine and naphthalene sulfonates were used in the main program and lignosulfate-based products in a subsidiary program. Some of these contained de-airing agents. The air-void distribution and the spacing factor were measured as well as the freeze-thaw resistance with deicing chemicals. When superplasticizers were used in a high-workability air-entrained concrete, the number of pores with a diameter up to 300 æm decreased, while the content of pores larger than 500 æm and the bubble spacing factor increased. Small pores coalesced and formed larger pores. Although the air content of the fresh concrete was sufficient, the superplasticized concrete sometimes had a spacing factor above 0.20 mm. For this reason, concrete with superplasticizers did not always have adequate freeze-thaw resistance. An influence due to the type of superplasticizer could not be detected, while the de-airing agents of the superplasticizers had a considerable effect. Some additional tests with plasticizers and retarders show that these admixtures also alter the air-void distribution or air-entrained concrete.