Effects of the incorporation of recycled construction and demolition waste (RCD) sand into composite mortars
Construction and demolition waste, recycled aggregate, coating mortar, granulometric composition.
The construction, remodeling 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 recycled aggregate is stored by plants. In this sense, the aim was to analyze the technical and economic viability of the use of RA with different grain size and washed quality
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 and microstructural properties of the aggregates and the fines fraction (<0.15 mm) were analyzed. Seeking to evaluate the technical feasibility of the mortar tests were carried out in the fresh state, which looked at the consumption of water, water retention, bulk density and air content embedded; and hardened mortar, compressive strength, flexural strength, dynamic modulus of elasticity, water absorption by capillarity, immersion absorption, adherence strength, susceptibility to cracking. The cost of production of 1 m³ of mortar was used for an assessment of technical 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 hardened mortar, such as mortars possessing RA with a presence of fines and not washed, more resistant, more rigid and less permeable. However, the performance of the coatings relative 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 technical feasibility, to incorporate RA, the cost to produce 1 m³ of mortar decreases. As a conclusion, it is recognized that the use of RA for the production of coating mortars is feasible, especially when aggregates with adequate granulometric composition and absent of fines are available.