Mini-slump: ensaio tradicional aplicado à avaliação da fluidez de geopolímeros à base de metacaulim

Abstract

The current work shows the feasibility of using the mini-slump test to assesses the workability and rheological properties of MK-based geopolymeric pastes. The study aimed to define standard test procedures, including video image analysis, and evaluate the effect of the activation conditions and their behavior over time. Eight geopolymeric systems were produced, where the type of activator (sodium or potassium), the alkali content (15 wt.% and 20 wt.%) and the water/binder ratio (0.70; 0.75 and 0.80) were assessed. The mini-slump test was carried out 8 minutes after the mixing beginning and repeated at 15-minute intervals until the paste achieved a high consistency. For each mixture, a video was recorded where the diameter of the spread paste over time were obtained through the ImageJ software. The yield stress was also estimated. A parallel plate rheometer was used to compare e validate the mini-slump test. As a result, spreading diameters between 50 and 222 mm, and yield stresses between 0.07 and 1.83 Pa were obtained. It was concluded that: (a) the mini-slump teste is applicable to evaluate flowability of geopolymers; (b) the image analysis improves the measurements’ accuracy and reliability; and (c) geopolymer’s flowability depends, mainly, on the nature of the activator, followed by the alkali content and the water/binder ratio.