Hydration properties of alkali-activated quick cooled copper slag and slow cooled copper slag

Abstract

The hydration properties of quick cooled copper slag (QCS) and slow cooled copper slag (SCS) activated with 4% and 8% (by Na2O mass) sodium hydroxide (NA) and water glass (NS) were investigated by hydration heat. Meanwhile, the hydration degrees and hydration products of alkali-activated copper slags were determined by X-ray diffraction, Fourier transform infrared, scanning electron microscope, energy-dispersive X-ray and backscattered electron tests. In addition, the compressive strengths of alkali-activated copper slag mortars were tested. Results show that alkali-activated QCS has significantly higher activities than alkali-activated SCS. At the concentration of 4%, the QCS activated with NA has a higher hydration heat than the QCS activated with NS, and the cumulative hydration heat of QCS activated with NS increases with the silica modulus at early ages. But this regularity generally reverses when the activator concentration is 8%. Meanwhile, elevated activator concentration could increase the cumulative hydration heat of QCS. In addition, with the increase in silica modulus, the second exothermic peak value decreases, the time of the second exothermic peak delays and the peak width increases. The hydration degree of QCS and the polymerization of amorphous hydration products increase with the silica modulus of activator. What’s more, the compressive strengths of alkali-activated QCS mortars and SCS mortars increase with the silica modulus of activator. When the silica modulus is more than 1, the compressive strength of the QCS mortar activated with NS could be qualified for common constructions.