Effect of Organic Admixtures on Activation Process, Rheological and Mechanical Properties and Durability of Alkali-Activated Slag Pastes and Mortars

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Title: Effect of Organic Admixtures on Activation Process, Rheological and Mechanical Properties and Durability of Alkali-Activated Slag Pastes and Mortars

Author(s): M. Palacios, F. Puertas, and P.F.G. Banfill

Publication: Special Publication

Volume: 239

Issue:

Appears on pages(s): 345-356

Keywords: admixtures; alkaline cements; durability; rheology; shrinkage; slag

Date: 10/1/2006

Abstract:
In the present work, the influence of two organic admixtures (a vinyl copolymer and one based on polypropyleneglycol in the alkaline activation process of blast furnace slag has been studied. The effect of these admixtures on the rheological and mechanical properties, volume stability and durability of waterglassactivated slag mortars has been studied. The incorporation of these organic admixtures delays the activation process of waterglass-activated slag pastes and, consequently, the initial and final setting time. The presence of the admixtures also increases the total heat released during the activation. Vinyl copolymer and shrinkage-reducing admixtures both decrease the yield stress of waterglass-activated mortars during the first minutes after mixing, and consequently, mortars with a lower liquid/solid ratio and higher mechanical strengths are prepared. On the other hand, the incorporation of the polypropyleneglycol admixture decreases the shrinkage of the alkali-activated slag mortars by up to 85%, however the vinyl copolymer increases the shrinkage significantly at RH=50%. The addition of the organic admixtures does not improve the durability of the alkali-activated slag mortars activated under carbonation. However, the incorporation of organic admixtures does increase the residual strength of the mortars after exposure to high temperatures.