Improvement of treated spent pot lining reactivity in cementitious material by calcination

Treating spent pot lining by the Low Caustic Leaching and Liming (LCLL) process creates an inert non-hazardous residue called LCLL Ash. Ground as a fine powder and calcined, LCLL Ash showed a pozzolanic behavior in cement. The effect of the calcination temperatures on LCLL Ash reactivity was studied by compressive strength activity index, Frattini tests, and RILEM R-3 tests, followed by XRD analysis. When calcinating LCLL Ash at temperatures below 800 degrees C, no differences in reactivity were seen between calcined and non-calcined LCLL Ash. At 800 degrees C, the formation of nepheline caused an alkalis uptake, showing a slightly lower reactivity of LCLL Ash than cement at 112 days. Beyond 800 degrees C up to 1200 degrees C, calcined LCLL Ash manifested better amorphization of phases and increased reactivity, similar to cement at 112 days. Finally, neither delay on hydration nor hydro-reactivity was observed with calcined LCLL Ash starting at 800 degrees C.