Search

The size of recent works in the city of Goiânia-GO has increased over the past few years, making it currently the largest building in Brazil located in this city. The executions of the foundation of these buildings have a high index of complexity due to the size, resistance characteristics of the concrete and great volume applied in the structural elements, in which it is necessary that the concreting is done, in some cases, in layers originating the cold joints. The purpose of the research was to analyze the behavior of different forms of cold joint execution, putting into practice possible connection methods between the concrete, always aiming at a better understanding of its effects when submitted to axial compression and bending traction test conditions. With the results achieved it is possible to determine that there was a difference, even if little, in the mechanical performance of the concrete. That is, the highest value of tensile strength in flexion was found in the specimen that used epoxy as a material between layers, in the case of prismatic and the lowest strength value in cylindrical specimen was also found when epoxy was used as a binding material between layers. [ABSTRACT FROM AUTHOR]

Samples of Banded Iron Formation (BIF) with different quartz and hematite contents were deformed in axial compression experiments in a Griggs-type apparatus, at T = 900°C, P =1.5 GPa and strain rates of 10-5 and 10-6 s-1. The aim is to investigate the mineral phase that controls the rheology of multi-phase rocks and to determine the processes that control the observed rock strength. BIF samples from Quadrilátero Ferrífero region-Brazil were cored perpendicular to the foliation, which is defined by parallel bands of quartz and iron oxide. Sample strength decreases with increasing hematite content and decreasing strain rate. At a strain rate of 10-5 s-1, samples with well-developed compositional banding showed higher strength. At the slower strain rate of 10-6 s-1 no difference between samples with or without compositional banding is observed. For comparison, at 10-6 s-1, the highest quartz content sample is as weak as the highest hematite content sample at 10-5 s-1. Strain is localized in hematite-rich layers. One intriguing observation is that quartz grains within the more deformed hematite-rich bands show more evidence for crystal-plastic deformation than grains in quartz-rich bands. [ABSTRACT FROM AUTHOR]