TECHNOLOGICAL QUALITY OF THE SAND USED IN CIVIL CONSTRUCTION IN MANAUS/AM

Abstract

The growing demand for sand in Manaus raises concern not only due to the environmental impacts resulting from extraction but also because of the lack of knowledge regarding its technological quality, that is, whether it meets the specifications defined by Brazilian standards. This research aimed to analyze the technological quality of the sands commercialized in Manaus. For the study, fourteen samples were collected and analyzed: eleven purchased from suppliers in eleven different neighborhoods, two from two rural roads identified as embankment sand, and one of alluvial origin from a shipyard. In the laboratory, granulometric, mineralogical, and chemical tests were performed, as well as X-ray fluorescence (XRF) and grain morphology analyses. The study also considered the geological origin of the sands, as it allows for the deduction of essential properties such as morphometry, granulometry, chemistry, and mineralogy. The sand supplied and sold in Manaus is mostly of alluvial origin, referred to as “washed sand,” and from upland areas (Spodosol and sandstone decomposition) from the São Francisco and Areal rural roads, referred to as pit or “embankment” sand. All analyzed sands presented clay lumps and fine material with a composition essentially quartzose and small amounts of mica. Morphology varied according to granulometry, as in the medium to coarse fractions most quartz grains are angular to subangular with low sphericity, while in the fine fraction they are subrounded to rounded with high sphericity. Although some samples showed clay lumps, fine material, and organic impurities above the limits established by NBR 7211/2005, this does not significantly compromise their quality for use in civil construction.