Avaliação da resistência à compressão do concreto usinado: comparação entre o método de moldagem remota e moldagem in loco

Abstract

The use of ready-mixed concrete is increasing in the last decades, as the pressure from the market to use a high quality product, using less storage spaces and less production of residuals also increased. For the quality control, compression tests are performed utilizing specimens, which are going to show if the concrete was made according to the designed load. The method utilized to do the molding of the specimens is the in loco molding, because this one has shown some difficulties to de done as: the lost of specimens at the construction site, high costs with the transportation of specialized people to collect the specimens, inappropriate material storage, and other. With this in mind, the metering plants companies have adopted a new methodology in order to achieve a better compression strength control, called remote concrete specimen molding. Thus, this research shows an experimental and theoretical overview about the comparison between the strength results from the remote and in loco specimens molding, focusing in constructions executed by HOBI e CIA LTDA in the cities of Pato Branco and São Mateus do Sul, in the state of Paraná. Concepts, properties, and the characteristics of the specimens molding are going to be presented, as well as an analysis of the comparative between the two kinds of molding of specimens studied: for the remotely molded specimen, the concrete is collected at the construction site and transported to the laboratory of the metering plant by the concrete mixer in sealed containers to be molded later, while the specimens molded in loco consists of molding the specimens at the construction site. Eight concrete specimens were molded at the construction site and at the metering plant, according to the NBR 5738 (ABNT, 2003), being tested twenty-eight days after they are collected, at the city of Pato Branco. In São Mateus do Sul, the same types of specimens collected by the metering plant were further analyzed. The compression strength results of both methods were compared and it was concluded that the strength of the specimens molded remotely were higher, but not significantly higher, than the ones molded at the construction site in both cities, however the standard deviation was higher. In short, the use of specimens molded remotely is satisfactory to the metering plants accordingly to its advantages when compared to the another method.