Recycling steel-manufacturing slag and harbor sediment into construction materials

Mixtures consisting of harbor sediment and slag waste from steel industry containing toxic components are fired to produce non-hazardous construction materials. The fired pellets become lighter as firing temperature increases. At a sintering temperature of 1050 degrees C, the fired pellets are in a form of brick-like product, while at 1100 degrees C, they become lightweight aggregates. Calcium silicate, kyanite, and cristobalite are newly formed in the pellets after firing, demonstrating that calcium oxide acts as a flux component and chemically reacted with Si- and/or Al-containing components to promote sintering. Dioxin/furan content present in the pure slag is 0.003 ng I-TEQg(-1) and, for the fired pellet consisting of slag and sediment, the content appears to be destructed and diminishes to 0.0003 ng I-TEQg(-1) after 950 degrees C-firing; while it is 0.002 ng I-TEQg(-1) after firing at 1100 degrees C, suggesting that dioxins/furans in the 950 degrees C-fired pellets have a greater chance to escape to atmosphere due to a slower sintering reaction and/or that construction of dioxins/furans from molten chloride salts co-exists with their destruction. Multiple toxicity characteristic leaching procedure extracts Cu, Cr, Zn, Se, Cd, Pb, Ba, As, and Hg from all fired products at negligible levels. (C) 2013 Elsevier B.V. All rights reserved.