A new method transforms industrial waste into cement
José Pichel Andrés/DICYT A group of the Research Centre for Ceramic Materials and Compounds (Centro de Investigação em Materiais Cerâmicos e Compósitos, CICECO) of the University of Aveiro has produced a new type of cement based on industrial waste. This new system, which has only so far been tested experimentally, needs less energy and uses only waste, which means that its implementation would reduce the environmental impact of the cement industry.
The industrial waste used in this study come from a local cellulose pulp and paper factory. To carry out the research the scientists took three waste types as a starting point: calcareous ooze, biosludge, and fly ash, which are generated at the chemical recovery centre at the sewage farm and at the thermoelectric power station of the factory. The cements that they produced are of two types: Portland cement or commercial cement and belite cement or low energy cement.
On comparing Portland cement produced by this new method with the conventional cement that the industry is currently producing, the researchers have found that “it possesses the same characteristics of durability and has the same physical properties but adds a very significant advantage, i.e. the reduction of the maximum firing temperature”, DiCYT was told by Leire Hernando Buruberri, the Spanish researcher who is a member of this group led by João Labrincha.
The industry uses a temperature of 1,450 degrees Centigrade while for this new cement 1,390 degrees will suffice. This lower temperature means a significant energy saving, “ considerably reducing the electricity bill of this sector and its environmental impact”.
On the other hand, low energy cement takes longer to acquire the desired properties of common cement in terms of resistance, but its firing temperature is also 1,350 degrees and moreover carbon dioxide emissions are reduced as the calcareous component in the mixture of raw materials is smaller. In short, the new process reduces the ecological footprint of this industry, which is responsible for 7% of global CO2 emissions. Moreover, “it is also important that these cements are produced exclusively from industrial waste without using non renewable natural raw materials such as clay or limestone”, the researcher points out.
The manufacturing process is a simple one; the industrial waste is mixed and is subjected to a temperature of between 1,350 and 1.390 degrees Centigrade. It is subsequently cooled at ambient temperature. In this initial stage the main component of cement, which gives it its properties, is obtained; it is subsequently ground and mixed with plaster to achieve the end-product.
In the opinion of the CICECO researchers, the results are so promising that after these experiments in the laboratory the product could make the leap into industry. 16 tons of industrial waste are needed to produce a ton of cement by this new method.