Expanded clay containing sludge generated in the paper pulp production process


The present invention relates to the use of sludge generated in paper pulp production process, in expanded clay formulations. The processing conditions control ensures consistency of sludge properties, in terms of chemical composition and particle size distribution. The sludge has a moisture content greater than 50%, which is almost entirely removed by drying. However, it can be used as it is processed. Formulations containing sludge amounts up to 50% (by weight), were tested. Keeping unchanged normal manufacturing conditions, products with functional properties similar to their counterparts are obtained without the waste addition. This solution has environmental added value, translated in the recycling of waste as raw material, thus saving natural resources. Furthermore, the strong exothermic decomposition suffered by the sludge allows reducing energy consumption in clay heating.

Innovative aspects & main advantages

The present invention is related to the incorporation of sludges from paper pulp plants in formulations based on clay minerals and used to produce lightweight aggregates. Maximum incorporation rates reached 20 wt%, without visible and functional negative impact in the properties of the final product or in the traditional lightweight aggregates processing conditions. This solution of recycling this waste presents a double environmental advantage preventing, on one hand, its landfill disposal for the paper pulp producer and, on the other hand, resulting in natural raw materials savings for the lightweight aggregate industry, leading altogether to the concept of efficient use of natural resources.


The main application of this invention is aimed on the lightweight aggregates producers as well as the paper pulp plants because it is an alternative for their sludge’s landfill disposal. End users of this product all systems using lightweight aggregates such as mortar and concrete producers.


Batista, João; Ferreira, Victor; Correia, António

Our Inventors


Universidade de Aveiro
Centro Tecnológico da Cerâmica e do Vidro
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