Application of paper sludge and clay in manufacture of composite materials: Properties and biological susceptibility

Abstract

With the aim of developing composite materials to be used on indoor wall systems, different composite materials (paper sludge (100 wt%) and paper sludge (60 wt% and 80 wt%) + clay (20 wt% and 40 wt%) were produced. Composite materials were tested for biological susceptibility, physic-mechanical characteristics (shrinkage, density, water erosion resistance, compressive stress at 10% relative deformation and Young's modulus, ultra sound propagation velocity, thermal conductivity) and microstructure. The granulometric composition of paper sludge and clay content of the samples are essential factors that affect the physic-mechanical characteristics of the composite materials. This study considered 2 types (S type and S* type) paper sludge granulometric compositions. S type composite materials (paper sludge particles were smaller than 8 mm) have the better thermal conductivity, S* type composite materials (paper sludge particles were smaller than 4 mm) show the better performances in terms of compressive stress at 10% relative deformation. Increasing clay content (20% and 40%, S* type composite materials) increases density, shrinkage, compressive stress at 10% relative deformation, also, decreases biological susceptibility (Rhizopus oryzae mould). The results showed that, all composite materials had bulk density around 0.65–1.12 g/cm3, shrinkage 1.7–6.0%, compressive stress at 10% relative deformation 0.95–7.0 MPa, thermal conductivity 0.072–0.154 W/(mK). Also, all composite materials have good resistance to water erosion.