Technological and environmental comparative of the processing of primary sludge waste from paper industry for mortar.

The pulp and paper industry traditionally generates large amounts of wastes at different stages of its production process, such as primary sludge that is extremely wet. The aim of this research is to evaluate a new process methodology aiming the incorporation of primary pulp and paper industry sludge waste, still in its liquid state, into cement and lime-based mortars. This procedure was compared with the incorporation of the waste in its dry state, which results from the traditional beneficiation process based on powder drying. Comparison was performed in terms of technological, durability and environmental performance of both wastes (liquid and dry) incorporated mortars, as well as with reference control mortar without incorporation. Two news models of liquid waste processing, for mortars incorporation, called thin and coarse liquid, were developed in order to evaluate technological parameters such as: consistency, entrained air, water retention, mass density, capillary absorption and mechanical strength. These parameters allow the characterization of durability, life cycle assessment and environmental conditions. Technological properties showed satisfactory results in mortars performance when waste was used as a thin liquid with nominal content (optimal mixture) similar to the reference composition. The air content of the mortar was 12% and the water retention 96.8%. In the hardened state, the optimal mixture had a mass density of 1.76 g/cm3, a capillary coefficient of 20.73 g/dm2.min1/2 and mechanical resistance to compression of 3.7 MPa and to flexion of 1.1 MPa, all results meet the limits of the literature for application in construction. It was found that the beneficiation process, which produces the thin liquid is the most efficient for the incorporation of waste into mortars when compared to the dry method. Indeed, the thin liquid waste incorporated mortars showed improved technological, durability and environmental properties. • Development of a new methodology for beneficiation of waste from paper industry. • Two liquid incorporation procedure were evaluated (thin and a coarse liquid). • The thin liquid (TL) presented the best technological and environmental properties. • The thin liquid (TL) can be used in mortars for civil construction. [ABSTRACT FROM AUTHOR]