Influence of Fineness and Vontent of Steel Slag Powder on Properties of Composite Admixture

Taking fluidity and compressive strength of mortar as index, steel slag slag composite admixture replaces cement by 50%. The influence of the fineness and content of steel slag powder on the properties of composite admixture was studied by uniform experimental design. The fitting regression equation between the parameters of steel slag fineness and dosage and the performance indexes is established, and the contour map is drawn. The results show that the predicted value is in good agreement with the measured value, and the correlation coefficient is more than 0.99. Through regression analysis and contour map analysis, it is shown that increasing the fineness of slag powder and reducing the content of slag are beneficial to improving the cementitious activity of slag composite.

Effects of Fluoride and Sulphate Mineralizers on the Properties of Reconstructed Steel Slag

Improving the cementitious activity and volume stability of steel slag by thermal reconstruction is an innovative method for efficient utilization of steel slag. In this study, different amounts of CaF2 and CaSO4 were added to steel slag as a mineralizer based on the determining admixtures needed for the reconstruction reaction, and the effects of CaF2 and CaSO4 on the cementitious activity and volume stability of the reconstructed steel slag were investigated. The results show that when the CaF2 content is increased to 5 wt%, the cementitious activity index of the reconstructed steel slag gradually increases to 92%, which is 12% higher than the first level technical requirement specified by the national standards, and the free CaO (f - CaO) and MgO (f-MgO) contents gradually decrease to 0.35 and 0.13 wt%, respectively. With increasing CaSO4 content, the cementitious activity index first increases and then decreases, while the contents of f -CaO and f-MgO show the opposite trend. When the CaSO4 content is 2 wt%, the activity index is 105%,which is 25%higher than the first level technical requirement specified by the national standards, and the f -CaO and f-MgO contents reach minima of 0.44 and 0.35 wt%, respectively.

Effect of Chemical Composition on the Properties of Reconstructed Steel Slag

The steel slag is not widely or extensively used because of its poor volume stability and low cementitious activity. In this paper, the solid waste fly ash, quicklime and slag discharged from iron and steel enterprises are used as conditioning components in the experiment. In order to improve the cementitious activity and volume stability of steel slag, the high temperature reconstruction experiment of steel slag was completed. The effects of C/S (2.50~3.14), S/A (4.5~17. 81) on the cementitious activity and volume stability of reconstructed steel slag were investigated by means of the tests of compressive strength, scanning electron microscope, X-ray diffraction, lithofacies test, stability test and so on. The results showed that the cementitious activity and volume stability of the reconstructed steel slag were improved in the higher C/S or lower S/A. The cementitious activity and volume stability of the reconstructed steel slag were improved with the increase of CaF2 content. By analyzing the cementitious activity and volume stability of the reconstructed steel slag, the optimum technological parameters are obtained as follows: C/S is 2.70 , S/A is 5.78, the content of CaF2 is 4%.

Effect of basicity on cementitious activity of modified electric arc furnace steel slag

Electric arc furnace steel slag was modified by wastes in hot-stage process with the aim to improve the cementitious activity. Effect of basicity on cementitious activity of modified steel slag was investigated in this research. The modified slag was characterized by XRD, DTA and Raman spectra techniques to investigate the correlations between structural features and the cementitious activity. The results showed that modified steel slag with a basicity index of 1.67 possessed the highest activity index, 107%, due to the precipitation of Belite, high content of amorphous phase and low polymerization degree. The polymerization degree of modified slag was demonstrated by nonbridging oxygen per tetrahedrally coordinated cations value which was calculated through curve-fitted Raman spectra. The value of modified slag increased as the basicity promoted from 1.05 to 1.67, indicating a lower degree of polymerization. Modified slag with a basicity index of 1.86 possessed the poor cementitious activity mainly because of the significant decrease of glass phase content.