Influence of Calcining Conditions on Pozzolanic Activity and Reaction Kinetics in Paper Sludge-Calcium Hydroxide Mixes

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Title: Influence of Calcining Conditions on Pozzolanic Activity and Reaction Kinetics in Paper Sludge-Calcium Hydroxide Mixes

Author(s): M. Frias, M.1. Sanchez de Rojas, and J. Rivera

Publication: Special Publication

Volume: 221

Issue:

Appears on pages(s): 879-892

Keywords: calcining conditions; paper sludge; pozzolanic material; reaction kinetics; waste

Date: 5/1/2004

Abstract:
The need to attain the correct assessment of industrial by-products and wastes re-quires an in-depth knowledge of their characteristics. One of the most important characteristics that affects in the aptitude of a thermally calcined product is the calcining conditions like temperature and stay in furnace. This is the aim of the current work which considers the importance of calcining conditions on the pozzolanic properties of a paper sludge as cementing material. The by-product used for this research is a Spanish paper sludge coming from a paper industry which uses 100% of recycled paper as raw materials. Due to the high content of organic material and calcium carbonate and, to the presence of different clayey minerals in sludge like kaolinite and talc, the calcining conditions play an important role on the mineralogy and pozzolanic activity of this sludge. For this reason, different intervals of temperature between 700 and 800°C and, different times of stay in furnace (2.5 and 5h) are studied in order to get the best pozzolanic properties for the paper sludge. The reaction kinetics of pozzolanic reaction cured at 40°C varied with the calcining conditions. The main crystalline phases identified by XRD were hydrocalumite (Ca4Al2O6C121OH2O) and calcium aluminium carbonate hydrate (Ca4Al2O6CO311H2O), stratlingite and hydrogamet.