Preparation of novel chemically bonded ceramics with steel slag and potassium hydrogen oxalate

Abstract

A novel chemically bonded ceramic (novel-CBC) is prepared based on the acid–base reaction of alkali metals in steel slag (SS) and oxalate anion (C2O42−) in potassium hydrogen oxalate (PO). The effects of SS/PO ratio and water–solid (W/S) ratio on the setting and compressive strength of novel-CBC were studied in this paper. Reaction products and microstructure of novel-CBC were characterized by X-ray diffractometer (XRD), field emission scanning electron microscope-energy dispersive spectroscopy (FESEM-EDS) and thermogravimetric analysis/differential scanning calorimetry (TG/DSC). An optimal formula is obtained at a SS/PO ratio of 3.0 and a W/S ratio of 0.20, which starts setting at 10 min and gives the strengths of 18.0, 25.0, 39.8 and 49.0 MPa at 1, 3, 7 and 28 days, respectively. The reactants from SS are mainly Ca-bearing phases, while only a small amount of RO phase is involved in reaction. The main reaction products of novel-CBC are calcium oxalate monohydrate (CaC2O4·H2O; whewellite) crystals and agglomerates consisting of K, Mg, Al, Si and O elements. The unreacted Ca-bearing phase particle and RO phase residue are embedded in a mixture of abundant CaC2O4·H2O crystals with smooth surfaces and a size of 0.5–1.0 µm with large amounts of the nanoscale agglomerates.