| Carbonation technology, may relieve the greenhouse effect by solidified CO2 permantly to store in some natural minerals or solid wastes. Meanwhile, the intensity of obtained minerals was enhanced. The optimum technological conditions of steel slag products prepared through carbonation had been explored by our study team. The carbonation steel slag powder brick had been also prepared. However, the carbonation increasing weight rate of steel slag was 9.48% which cannot be reached to the theoretical value 37% all the time. On this basis of the study, the influence of admixture, pH value and hydration time on the steel slag carbonation was discussed, in this paper. The key factor of steel slag was explored. So the best way of improving steel slag carbonation reaction was found. The phase composition, microstructure and morphology of steel slag structure carbonated were analysed by XRD and SEM-EDS. Meanwhile, through the study of the carbonation reaction of steel slag minerals, mineral of steel slag participated in carbonation reaction was determined. And the carbonation reaction equations of mineral were derived, the reaction mechanism was also studiedBy researched the effect of admixtures on carbonation of steel slag, the followed conclusions were obtained. The addition of admixtures such as NaHCO3, Na2SiO3 and sodium carboxymethyl cellulose was beneficial to improve the carbonation increasing weight rate of steel slag powder brick. However, the strength of sample was decreased with the increasing of sodium carboxymethyl cellulose. The sample of carbonation increasing weight rate was 9.48%, meanwhile, the compressive strength was 17.8MPa, when 1% sodium carboxymethyl cellulose+1%NaHCO3 were added and carbonation time was longer than 2h. The sample of carbonation increasing weight rate and compressive strength were reached to 11.24% and 34.1MPa, respectively, when 0.4% Na2SiO3+1%NaHCO3 were added.By adding solutions with the pH value 1.87-13.12 to sample of steel slag powder, the influence of pH value on the carbonation of steel slag was studied. The experiment results show the pH value of solutions is 6.08 and 12.55 respectively, the carbonation increasing weight rate was generally higher. This indicated that weak acid and alkali environment were benefical to steel slag carbonaton, and when steel slag sample was curing 1d and mixed with the pH value of solutions of 12.55 and 6.08, the maximum compressive strength could reach 68.1MPa and 67.7MPa respectively. Moreover, carbonation weight increase of pH value of 12.55 was slightly higher than pH value of 6.08. When slag sample was curing 7d, the pH value of solutions is 12.55, the sample of carbonation weight increase rate was the highest, reached 10.27%. The above results revealed that the slag sample of carbonation reaction was conducted easier in alkaline environment. In this paper, the effect of hydration on carbonation of steel slag through various steel slag maintenance time was studied. The results show that the carbonation weight increase rate was relatively high during early stage, namely hydration time between 2h and 6h, which was decreased at the later stage. It was indicated that the long hydration time was not good for carbonation reaction. Comparison with C3S and C2S, CH was apt to carbonation reaction at the later stage of hydration. CaCO3 shell obtained at the surface was prevented to the carbonation reaction.Carbonation reaction could been occured in steel slag minerals (C3S, C2S, C4AF, Ca(OH)2, C3A, Mg(OH)2, CaO, MgO), The degree of carbonation of different minerals were Ca(OH)2ï¹¥Mg(OH)2ï¹¥C3Sï¹¥C2Sï¹¥CaOï¹¥MgOï¹¥C4AFï¹¥C3A. The carbonationg increasing of powdery Ca(OH)2 was the highest, which reached 47.62%. The influence of hydration on single mineral was studied. The results show that the carbonation increasing weight rates of C3S, C2S, C3A and C4AF were all increased with the passage of hydration time. However, the carbonation increasing weight rates of C3S and C2S were increased rapidly when the hydration time between 2-10h, otherwise which were increased flat after 10h. |
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