Análise da composição de agregados naturais e reciclados para a produção de argamassas

Abstract

Due to increased material consumption to meet the demand for mortar and concrete production in civil construction, there is a need for greater acquisition of fine aggregates for the formulation of these cementitious mixtures. Understanding the limitation of natural aggregate extraction and recognizing that construction and demolition waste are useful materials for obtaining recycled aggregates, there is a notable interest in their utilization to fully or partially replace natural aggregates in cementitious materials. This study aimed to investigate compositions of natural and recycled fine aggregates for mortar formulation. The methodology involved the characterization of fine aggregates and the analysis of their properties, as well as the study of particle size distributions among two types of natural fine aggregates and three derived from demolition waste beneficiation. Composition studies involved simulations of sand mixtures using Excel software, wherein, with data on the particle size distribution curves of the five aggregates, combinations of natural and recycled fine aggregates were made, with the replacement portion of natural material ranging from 10% to 90%. Using the results of the aggregate compositions obtained numerically, particle size distribution curves were plotted, and situations where the curves were within the optimal zone, as defined by NBR 7211, were observed. From these curves, two combinations were chosen for each type of composition, selecting cases with the highest percentages of recycled material. For these combinations, bulk density tests were performed to determine their void index. Recognizing that a lower void index of aggregates results in mortar mixtures with higher compressive strength, this criterion was used to define the compositions of aggregates to be used for mixture production. Consequently, six mortar mixtures were chosen for testing, with a fixed ratio of 1:2:0.6 for all productions. The mortars were analy ed through consistency index tests, fresh state density, flexural tensile strength, and c ompressive strength at 28 days. The results remained within the values identified in the literature and standards. For the consistency index tests, values ranging from 303 mm to 341.8 mm were obtained. For the fresh state specific mass tests, values ranging from 2192.36 kg/cm³ to 2258.14 kg/cm³ were obtained. For the 28-day flexural tensile strength tests, values ranging from 1.39 MPa to 1.8 MPa were obtained. For the 28-day axial compressive strength tests, values ranging from 19.13 MPa to 24.78 MPa were obtained. Finally, among the compositions studied, for future production of structural concrete, due to the results of the mixture tests in both fresh and hardened states, the combination AMNF (60%) + ARSM2 (40%) is recommended.