Evaluation Of The Reactivity Of Treated Spent Pot Lining From Primary Aluminum Production As Cementitious Materials

Aluminum Spent Pot lining (SPL) is an industrial hazardous waste generated from aluminum electrolysis cells. The SPL separates in two parts, the first cut is rich in carbonaceous materials and the second cut is rich in vitrified refractory. Treating second cut SPL by the Low Caustic Leaching and Liming (LCL&L) process generates an inert non-hazardous residue, called LCLL Ash. This product is mainly composed of stable crystalline phases such as corundum, albite, nepheline with some amount graphite. Ground as a fine powder, LCLL Ash could be used in cement as a supplementary cementitious material (SCM). This paper focuses on the investigation of LCLL Ash reactivity and its improvement by calcination at 1050 degrees C. Reactivity was evaluated with multiple tests, such as compressive strength activity index, Frattini test and Rilem R-3 tests followed by XRD analysis. An inert SCMs (limestone, filler, and quartz) and reactive SCMs (slag, fly ash, silica fume) were used as references. The results show that LCLL Ash in cement shows inert properties similar to quartz with a retarder effect below 7 days and a high alkali content. Moreover, the temperature of the Rilem R-3 tests, shows expansion in the paste due to LCLL Ash hydro reactivity. This expansion was not observed with LCLL Ash blended cement mortar. Calcination improved significantly the reactivity of LCLL Ash by generating higher reactive silica and alumina content. Notably, calcined LCLL Ash showed reaction properties similar to a calcined clay. Finally, neither delay on hydration nor expansion was observed with calcined LCLL Ash.