Effect of the Addition of Aluminum Recycling Waste on the Pozzolanic Activity of Sugarcane Bagasse Ash and Zeolite

The pozzolanic activity of aluminum recycling waste (AW) was evaluated along with sugarcane bagasse ash (BA) and zeolite (ZE) to give a more sustainable use. These materials were characterized and submitted to the pozzolanic activity test by a modified Chapelle test and the compressive strength of mortars prepared with limestone Portland cement (LPC). The final solids were characterized again to determine the hydrated products. The main reactive chemical components of AW are Al2O3 and MgO, which are in the form of hydroxides, such as nordstrandite (Al(OH)3), meixnerite ([Mg5Al3(OH)16][(OH)3·(H2O)4]), brucite (Mg(OH)2) and magnesium chloride hydroxide hydrate (Mg3(OH)5Cl·4H2O). All of the studied materials were classified as pozzolans by the modified Chapelle test, and the main hydrated products formed in the AW sample were katoite, ettringite, talc and amesite. When mixed with BA and ZE, C-A-S-H and C-S-H phases were also formed. The C-S-H phases and portlandite were detected only in the solids of the modified Chapelle test of BA and ZE. Calcite was present in all samples, indicating that part of the Ca(OH)2 was consumed by the carbonation process. The compressive strength test of mortars revealed that only ZE is a pozzolan. In mortars containing AW the production of ettringite and calcium carboaluminate increased due to the reactions of aluminum, respectively, with gypsum and calcite present in LPC. In addition to portlandite, C-S-H was formed only in the BA and ZE mortars. Although hydration reactions were not sufficient to form C-S-H in AW mortar, reactive aluminum favors the formation of primary ettringite.