Efeitos da incorporação de areia reciclada de resíduos de construção e demolição (RCD) em argamassas mistas de revestimento

Abstract

The construction, reform and demolition process can cause significant problems to the environment due to the extraction of raw materials and an inadequate disposal of the waste generated. In particular, construction and demolition wastes (CDW), which commonly correspond to more than half of urban solid waste, have as main destinations, vacant lots, roadsides and rivers, causing serious environmental, social and economic impacts. Currently, a recycling of recycled aggregates (RA), especially of mixed composition has been studied to lesser extent when compared to RA of concrete. Therefore, because it does not have alternatives for their use, a large amount of this type of RA is stored by plants. In this sense, the aim of this research is to analyze the technical and economic viability of the use of RA with different grain size and washed condition compositions, at 25, 50, 75 and 100% substitution levels of the natural aggregate (NA), in the production of mixed mortars. For the production of mortars, CP II Z-32 cement, lime CH-I and a volume ratio of 1:1: 6 were used. Water content was adjusted to mixtures with a consistency of 260 mm. Initially, the physical, chemical, mineralogy and microstructural properties of the aggregates and the fines fraction (<0.15 mm) were analyzed. Seeking to assess the technical feasibility of mortars were characterized fresh, through consistency tests, water retention, bulk density and entrained air content. And in the hardened state, the compressive strength, flexural tensile strength, dynamic modulus of elasticity, water absorption by capillarity, immersion absorption, adherence strength and susceptibility to cracking. The cost of production of 1 m³ of mortar was used for an assessment of economic feasibility. It was showed that, as mortars with RA, regardless of their size distribution or condition, presented higher water consumption, lower bulk density and incorporated air content, as well as water retention capacity. In the hardened state the mortars had RA with the presence of thin, had higher resistance, higher modulus and lower porosity and permeability. However, the performance of the mortar coverings to the potential of adhesion to the substrate and a number of cracks has been lower, confirming a premise that the use of RA with fines is not indicated for coating mortars. As for the economic feasibility, to incorporate RA, the cost to produce 1 m³ of mortar decreases. However, it is recognized that the use of RA for the production of coating mortars is feasible, especially when aggregates with adequate size distribution are available, without fines and in washed condition.