Natural hydraulic lime mortars - The effect of ceramic residues on physical and mechanical behaviour

In the past, it was common the use of ceramic residues as a pozzolan and/or aggregate in air lime mortars and concrete. Nowadays, incorporating ceramic residues in mortars is one of the ways to increase sustainability of the construction sector and introduce some benefits in the properties of those mortars. Ceramic residues were collected from several ceramic industries, namely from bricks, roof tiles and pots production, milled in laboratory and incorporated in natural hydraulic lime (NHL) mortars. Two distinct groups of mortars were prepared, with two different proportions, and samples were produced. A group with a volumetric proportion of one part of NHL and three parts of aggregate (1:3) and three different percentages of replacement of the aggregate by each of the residues (0, 20 and 40% in volume) and a second group with a volumetric proportion of one part of NHL and four parts of aggregate (1:4) and percentages of replacement of 0 and 30% were prepared. Their behaviour was analysed by determining its properties after 28 days of curing. The incorporation of ceramic residues in the NHL mortars led to an increase in open porosity, capillarity water absorption and water vapour permeability but also an increase in dynamic elasticity modulus and mechanical strengths. This increase was more significant for higher replacement percentages. The behaviour of these mortars seems appropriate for new construction renders and plasters but caution must be taken concerning moisture migration, namely when used in rehabilitation.