Preparation and properties of high-strength lightweight aggregate ceramsite from nepheline tailings

Nepheline tailings (NTs) were made into pellets and then transformed to lightweight aggregate ceramsites by sintering approach, the effects of mix composition and sintering process on air-void structure and performance were studied. The results show that introducing mineralizer, rising sintering temperature and extending holding time increased air-void size, decreased density, reduced cylinder compressive strength and rose water absorption of NT-based ceramsite. Acceleration of heating rate led to the increase of density, resulting in strength enhancement, but heating rate of 20 celcius/min caused uneven air-voids, weakening strength. Dense enamel layer on surface, suitable air-void structure and well-crystallized nepheline of ceramsite contributed to preparation of high-strength lightweight ceramsite with a NT content of 93 % to 97 %, bulk density of 577 kg/m3 to 823 kg/m3, cylinder compressive strength of 4.3 MPa to 9.3 MPa and a low water absorption of 0.3 % to 0.8%