Landmark Series: Performance of Superplasticizers in Concrete: Laboratory Investigation-Part I


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Title: Landmark Series: Performance of Superplasticizers in Concrete: Laboratory Investigation-Part I

Author(s): V.M. Malhotra and D. Malanka

Publication: Concrete International

Volume: 26

Issue: 8

Appears on pages(s): 1-35

Keywords: admixtures; air entrainment; bubbles; compressive strength; concretes; flexural strength; freeze-thaw durability; high--strength concretes; laboratories; mechanical properties; plasticizers; segregation; slump tests; tests; water-reducing agents.

Date: 8/1/2004

Superplasticizers are new types of water reducers which, when added to concrete, cause large increases in its workability. The introduction of these water reducers has opened up new possibilities for concrete in construction. This report gives results of a laboratory investigation to determine the performance of superplasticizers in high-strength concrete with a water-cement ratio of 0.42. A series of 15 concrete mixes was made at a water-cement ratio of 0.42 with a slump of 2 in. {50 mm). various dosages of the superplasticizers - Melment L10, Mighty 150 and Mulcoplast Cr - were added to the mixer after completion of initial mixing. This was followed by additional mixing for 2 minutes. Apart from one control concrete mix, all others were air-entrained. Initial setting times of concrete, increases in slumps, and their subsequent loss with time were recorded. A number of test cylinders and prisms were cast for determining mechanical strength and freeze-thaw durability. Incorporating superplasticizers delayed initial setting time of concrete depending on the type and dosage used. The large increases in slump of superplasticized concrete were confirmed; how-ever, the increased workability and its loss with time were functions of the type of superplasticizer used. The compressive and flexural strengths of the test specimens cast from superplasticized concretes were comparable to or greater than those of the control specimens. The test cylinders cast without external vibration showed strengths comparable to those using external vibration.