Análise da resistência de traços populares de argamassa em diferentes tempos de preparo

Abstract

Some constructive vices are common in Brazil, and one of them is the use of mortar after a few hours of its preparation, mainly in the case of the lunch break. In these cases, the mortar may be being used after the start of setting, that is, after the start of solidification of the cement paste. In this case, some properties of the mortar may change, including resistance. The object of study was the analysis of resistances to axial compression and to traction in flexion, described in NBR 13279 (ABNT, 2005), of three different mixes of mortar, 1:3, 1:3 with additive and 1:2 :8, considering three different preparation times: the immediate preparation time, one hour after preparation and two hours after preparation. For each trait, 27 specimens were molded, 9 for each failure date (3 days, 7 days and 28 days). Of the 9 for each breakout date, 3 were cast in immediate time, 3 in one hour, and 3 in two hours. The results of the study showed that both the flexural strength and the compressive strength regressed, in general, with the increase in the preparation time interval, in all traits. Thus, the study showed that mortars with preparation time over one hour already have a drop in resistance values.