Influence of carlin-type gold mine tailings addition on the synthesis temperature, alkali-resistant performance, and hydration mechanism of Portland cement

The massive discharge of carlin-type gold mine tailings (GMT) has caused serious harm to the environment, such as occupying land and building tailings dams. However, GMT is rich in SiO2 and CaO, which is likely to be a material for the synthesis of Portland cement in theory. Thus, this work synthesized four Portland cement with GMT addition of 0.00, 5.00, 10.00, and 15.00 wt%, and investigated their synthesis temperature, mineral phase composition, alkali-resistant performance, and hydration mechanism via the CaO free test, X-ray diffraction, compressive strength ratio, electron microscopy, and thermogravimetric analyzer. Results show that the syn-thesis temperature decreases by 100 degrees C when the GMT addition in raw materials exceeds 10.00 wt%. The mineral phase composition of these synthesized Portland cement is alite, larnite, tricalcium aluminate, and tetra-calcium aluminoferrite; their hydration phase is rod-like AFt, nubby CSH, and sheet-like Ca(OH)2; both are the same as that of Portland cement without GMT. Results also show that the Portland cement synthesized with 10.00 wt% GMT performs better on the compressive strength (24.7/18.5 MPa at 7 days and 56.1/48.6 MPa at 28 days) and alkali-resistant (0.75 at 7 days and 0.87 at 28 days) since the highest output of the total AFt and CSH (8.50/ 13.25 wt% at 7/28 days) and the Ca(OH)2 (5.89/11.57 wt% at 7/28 days). This work proves that GMT as a material for the synthesis of Portland cement is viable, and provides an effective method for the resource uti-lization of GMT.