Analysis of the compactness and properties of the hardened state of mortars with recycling of construction and demolition waste (CDW)

Several countries in the world have experienced considerable economic growth in the construction sector in recent decades, culminating in the demolition and reconstruction of large structures of reinforced concrete, that produced large amounts of solid waste. Much of this construction and demolition waste (CDW) is deposited in landfills, which generates high costs. The objective of this work is to evaluate the use of CDW as a replacement of natural sand in coating mortars. Four mortar mixtures, 1:1:6 (cement:lime:natural sand), with partial and total substitutions of the natural sand were investigated for CDW addition of 0 (reference), 25, 50 and 100 wt.%. Physical characterization of the CDW was carried out by particle size analysis while chemical composition was disclosed by EDX. Technological properties related to mortar fluidity, mechanical strength, mass density and water absorption by capillarity as well as environmental characteristics associated with leaching and solubilization of mortars, were evaluated. In addition, the compactness of the material was verified through Rene Feret's law. The results demonstrate that the substitution of more than 25% CDW for sand requires relatively larger amounts of water in the mortar. With regard to the degree compactness, the use of CDW improves the degree of compaction of the evaluated mortars and increase the compressive strength. However, the water absorption of the mortar increased with the levels of incorporated CDW. Therefore, to attend standard requirements for mortars, it is not possible to use CDW contents above 25%. (C) 2020 The Authors. Published by Elsevier B.V.