Effect of Al2O3 on the Structural Properties of Water-Quenched Copper Slag Related to Pozzolanic Activity

Abstract

Water-quenched copper slag (WCS) modified with alumina (Al2O3) has been proven as a cement substitute; however, the effect of Al2O3 on structural properties of WCS related to pozzolanic activity has not been well investigated. The structural properties and the pozzolanic activity of WCS with different amounts of Al2O3 are characterized by X-ray diffraction, differential scanning calorimetry, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and the uniaxial compressive strength test. The results show that only amorphous exists in copper slag, and the stability of amorphous first increases and then decreases with the increase in the alumina content. The addition of alumina significantly improves the pozzolanic activity of WCS at 7 and 28 days, but it has little effect on the pozzolanic activity of WCS when the slag’s curing age is 3 days. The results also show the increase in the non-bridging oxygen content, the decrease in the degree of polymerization, and the transition from Q2 and Q4 to Q3 with the increase of alumina content. Moreover, the addition of aluminum will convert Si-O-Si into Si-O-Al. These experimental results show that the addition of alumina can improve the pozzolanic activity of WCS, which can be used to partially replace cement.