Aplicação de areia de britagem de rochas basálticas na fabricação de concreto de cimento Portland

Abstract

Despite the technological advances on the structural concrete production, in natura materials are still used. This fact has been causing environmental and economic problems to the manufacturing chain. One of the problems is related to the sand extraction from riverbeds, this is the reason why professionals involved with concrete technology are searching for alternatives to the use of this type of sand in the structural concrete manufacturing. One alternative that is being studied in various parts of the country, because its large availability is a sand produced from the rocks´ comminution, called crushing sand. In the Caxias do Sul region there are large reservations of basaltic rocks origin (Riodacitos), from which it is possible to produce this type of sand. In this work, it was evaluated the feasibility of substitute natural sand for crushing sand from basaltic rocks produced in five mining companies located at Caxias do Sul region. The study was developed in three stages: on the first one, the features of the sand that arises from rocks´ mineralogy and petrography and from the mining manufacturing process were evaluated; on the second the concrete properties through the EPUSP/IPT dosage method were evaluated; on the third they were produced specific trace to each type of sand in order to verify the efficiency of the dosage method. The characterization results established that the crushing sand have different features IF compared with natural sand and that Just two out of Five evaluated sands presented properties that allow its use in structural concrete. The properties arising from the fabrication process, for example the presence of powder material, the grains´ shape and texture caused the raise of the plaster content, which influenced directly on the constituents materials proportioning. The results of the concrete properties evaluation showed that, for the same trace, the resistance to axial compression and the elasticity module are smaller in the concretes produced with crushing sand. If the plaster content is corrected and the specific traces are produced for each type of sand it is possible to produce concretes with desired resistance. In spite of the differences found on the sand properties it was proven that the crushing sand produced at the Caxias do Sul region can be used on the portland cement structural concrete production, replacing totally the natural sand used.