Efeito do procedimento de mistura no comportamento no estado fresco de argamassas de revestimento produzida em obra e industrializada

Abstract

The sequence with which materials are added to the mixtures influences the behavior of fresh mortars and will reflect on the quality of the coating. Therefore, the aim of this article is to analyse how different types of mixtures procedures interfere on the fresh behavior of two different types of mortar - industrialized coating mortar (AI) and mortar produced on site (APO). In this research, the four types of mortar mixtures adopted to analyze the mortar behavior were: manual mixing with free water (MAL), powder on water mechanical mixture (PA), water on powder mechanical mixture (AP) and manual mixture with fixed water (MAF). The mortars were submitted to tests for the determination of fresh density and trapped air content and also characterized rheologicaly by the Squeeze-flow method. This last analysis was performed at time zero after mixing (T0) and 20 minutes after mixing (T20). After mixtures the mortars were tested for fresh density, incorporated air content and rheological behavior by Squeeze-flow method. This last test was made immediately after mixture (T0) and twenty minutes after mixture (T20). The results indicated the presence of an additive incorporating air in the industrialized mortar, since this type of mortar presented high air content when compared to the mortar produced on site. In contrast, the mixtures produced by hand presented less air entrapment when compared to the mechanical procedure in the mortar. The mixing procedure had a significant influence on the performance of the industrialized mortar, probably due to the presence of the air -entraining additive. Mortars produced on site, which had no additives, showed similar performances for both mixing methods.