Mechanical behavior and durability of mortars with quartzite and Portland cement after sulfate attack

Resumo

The residues of ornamental rocks, especially quartzite, cause great environmental impact. More impulse has
been given to research on the recycling of these residues over the last years, particularly for use as aggregates
in concrete and mortar. Nevertheless, the studies conducted so far do not mention the behavior of the mortar
blended with aggregates coming from residues of ornamental rocks when under chemical attacks in sulfaterich
environment. Thus, in the present study it was sought to add quartzite residues to the mortar, verifying
its mechanical behavior and its durability when attacked by sodium sulfate (Na2SO4). The durability of the
mortar blended with quartzite residues under sulfate attack was evaluated by the dimensional variation of the
test specimens when immersed in sodium sulfate solution, according to the methodology of the NBR 13583
standard. Were used the following complementary techniques: simple compressive strength, X-ray diffraction
and thermogravimetric and differential analysis. From the tests, it was verified that the mortars, after
attack of sodium sulfate, presented dimensional expansions superior to 0.06%, as well as increased mechanical
strength. Therefore, although it was found that the specimens incorporated with quartzite residues were
attacked by sulfate, it was observed that it was not able to form sufficient secondary ettringite to mechanically
damage the specimens submitted to the sodium sulfate attack.
Keywords: Alternative materials, quartzite residue, sulfates, durability.