Evaluation of the pozzolanic activity of peat in Portland cement

Reference Presenter Authors
04-002 Sylma Carvalho Maestrelli Oliveira, D.C.(Universidade Federal de Alfenas); Cruz, C.M.(Universidade Federal de Alfenas); Grillo, K.F.(INSTITUTO FEDERAL SUL DE MINAS); Del Roveri, C.(Universidade Federal de Alfenas); Grillo, R.F.(INSTITUTO FEDERAL SUL DE MINAS); Maestrelli, S.C.(Universidade Federal de Alfenas-campus de Poços de Caldas); Cement is one of the most used materials in the world. There are different types of Portland cement; among them, there is the pozzolanic type, in which a pozzolanic material is added to the cement and form compounds with binder properties. Peat is an organic compound and its chemical composition is similar to the pozzolans. The present work aims to evaluate the pozzolanic potential of peat when it is added to the cement in the proportions of 5, 10, 15 and 20%wt. X-ray fluorescence and diffraction tests were performed for the characterization of the cements and peat separately, and also fineness tests, water in the paste of normal consistency, initial and final set time, air permeability, bulk density, expandability and mechanical resistance. X-ray fluorescence and compressive strength tests were performed for the cement and peat compositions at the age of 28 days; porosity tests and scanning electron microscopy (SEM) were performed too. The results showed that the combination of chemical and physical properties of each studied cement corroborates its mechanical behavior and the final properties acquired during the curing process. For the compressive strength of compositions, for every content studied, regardless of age or cement used, there is a reduction of 70% in the mechanical resistance, resulting in values lower than those of pure cements. Considering that the porosity values remained constant for all compositions, it can be considered that peat, although presenting granulometric distribution according to the standard, shows no pozzolanic activity. SEM confirms the results of mechanical resistance: for the formulation with 5% of peat addition it is possible to identify the hydration products through the microstructure and chemical composition presented. However, in the formulation with 20% of peat addition, the microstructure changes drastically for the three cements, presenting areas that did not go through the hydration process.
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