Influence of Modifier Admixture Based on LAS in Cement Pastes

The use of modifying admixtures in cement-based composites is mandatory to improve their physical properties with technical and economic advantages. This paper discusses the influences of an alternative admixture based on linear alkyl benzene sodium sulfonate (LAS) in cement pastes. Rheological tests were carried out on a flow table. Setting times and reaction speed were evaluated by ultrasonic pulse velocity (UPV) measurements. Compressive strength tests were performed in mortars. Different LAS contents were evaluated (0, 0.01, 0.1, and 1.0% by cement mass). Contents of up to 0.1% of LAS did not significantly change the rheological behavior in comparison to the reference paste, whereas the content of 1.0% of LAS showed a clear plasticizer effect. The highest levels of LAS resulted in an acceleration in the setting times, which contrasts with the results of UPV. Contents of 0.01 and 0.1% did not impair the strength in the first ages.