Effect of high temperature modification on the highly adsorptive manufactured sand dust concrete

Abstract

The production process of manufactured sand generates a large amount of dust, which poses a serious threat to the environment. In this study, we selected highly adsorptive manufactured sand dust of three lithologies (diabase, tuff, and basalt) for high temperature calcination. We evaluated its mechanical properties and microstructures after high temperature modification using various characterization methods to investigate its feasibility as a supplementary cementitious material (SCM). A comparative analysis of the manufactured sand dust before and after modification was conducted using thermogravimetric-differential scanning calorimetry (TG-DSC), laser particle size analysis, X-ray diffraction (XRD) and X-ray fluorescence spectrometry (XRF) techniques, the results showed that high temperature modification can reduce the crystallinity of the mineral impurities in the manufactured sand dust. Furthermore, the average particle size of artificial sand dust from all three lithologies (diabase, tuff, and basalt) was reduced. However, the flowability of the mortars increased by 12.1%, 7.4%, and 6.4% respectively. The 28-day volcanic ash activity index reached 63%, 61%, and 60% respectively. In addition, we used the modified manufactured sand dust as a supplementary cementitious material in concrete. It was found that when 30% of cement was replaced with a 1:2 mixture of manufactured sand dust and fly ash, the compressive strength at 90 days reached a maximum of 90.6 MPa. These results demonstrate that the modified manufactured sand dust has certain economic benefits and can be used to partially replace cement in concrete. This provides a basis for the development and application of highly adsorptive manufactured sand in the long term.