Rheological Properties of Grouts Formulated with Sludge from the Water Treatment Industry

Water treatment for drinking water supplies typically involves several processes during the purification of raw water. As a result of this process, water treatment plants produce waste known as water treatment sludge. Currently, one of the most common uses of this sludge is to be disposed of in landfills or discharged into rivers and streams, with associated environmental impact due to the huge amounts of this waste. On the other hand, the construction industry has significant environmental impacts resulting from the extraction and use of non-renewable natural resources as raw materials, as well as high carbon dioxide emissions associated mainly with the production of binders such as cement and hydraulic lime. In view of these facts, this study used water treatment sludge as a partial substitute for the binder in grouts for consolidating stone masonry walls. Grout injection is a consolidation technique that allows to increase the compactness of the masonry and thus improve its monolithic behaviour. Most consolidation inventions involve the use of significant amounts of grout, so replacing the binder with this waste may be a possible to produce of environmentally friendly grouting materials. Within the framework of this study, the rheological characterisation of the grouts prepared with these calcined and uncalcined wastes as raw material is carried out up to a dosage of 15%, replacing hydraulic lime. The results of the viscosimetry measurements show a significant difference in the plastic viscosity of the grout with the introduction of this waste, especially at dosages above 10%. It has been verified that the calcined waste further penalises the fluidity of the grout.