Ceramic wastes as raw materials in portland cement clinker fabrication: characterization and alkaline activation

Abstract

The world-wide cement industry is seeking experimental avenues that will lead to cement production that is less energy-intensive, less damaging to the surrounding environment and less prolific in GHG emissions. In Spain and Europe in general, this approach is wholly consistent with the concept of sustainability and compliance with the Kyoto Protocol. The use of different kinds of industrial waste and by-products as alternative materials in cement manufacture has proved to be a very effective way of contributing to such sustainability. These alternative materials may be incorporated during cement production by partial/y replacing conventional fuel and/or the raw materials ground into the raw mix, or by including active additions to the cement and/or clinker. The present paper discusses the preliminary results obtained in a study of the composition and alkali activation of six types of fired ceramic waste with a view to their viability as partial replacements for some of the prime materials used to prepare raw mix for Portland cement. The results show that the chemical and mineralogical composition of the six materials makes them apt for such possible use. They are neither toxic nor radioactive. And as might be expected this type of waste exhibits pozzolanic activity. Alkali activation of the waste, low at the age analyzed (8 days), does not appear to be affected by the vitreous phase content or the nature of the activator. The characterization study conducted on the activated paste shows that the feldspar phases are the ones most susceptible to dissolution and reaction with the alkaline solutions.

Keywords

• cement manufacture
• ceramic waste
• characterization
• alkali activation
• pozzolanicity