| Nowadays with the development of the steel industry, the speed of steel slag discharge obviously increases. A large amount of steel slag not only occupy large tracts of land, but also pollute the environment. A large number of steel slag(residue)for magnetic separation was produced by the hydro-ball-milling technology, washing and separation. It is difficult to reuse due to large content of water. In this thesis, the residue was reused by preparing the autoclaved aerated concrete(AAC) block in replace of lime and Portland cement. The influence of the ration, the fineness of raw materials and the main autoclaved products of the AAC block on the compressive strength were investigated. And also, hydrothermal treatment of residue-quartz was studied. The specific research contents and results are as follows:1. By studying the influence of the ration and the fineness of raw materials on the compressive strength of the AAC block, the optimum ration of the raw materials is as follows: m(residue): m(sand): m(cement): m(lime): m(gypsum)=38: 40: 6: 14: 2,the content of aluminum powder is 600 g/m3, and the compressive strength of the obtained block is 4.10 MPa. The compressive strength is increased by decreasing appropriately the fineness of residue and sand and the remainder of 80 um sieve of the residue and sand control in 10%~15% is appropriate.2. The AAC block was characterized by XRD and SEM. The results exhibited that the main autoclaved products of the AAC block were the plate tobermorite,fibroid hydrated calcium silicate(B) and xonotlite. When they mixed grow, the aerated concrete has high strength. EDS showed that there were about 1% Al2O3 and no Fe2O3 in tobermorite solution, and there were more ions in the fibroid hydrated calcium silicate(B), including Al2O3, Fe2O3 and Mn O.3. By comparing the hydrothermal treatment of the two systems of residue-quartz and lime-quartz, the results are as follows:(1)Elevated temperature is conducive to the rate of hydrothermal treatment. With increasing the reaction temperature from 130 o C to 210 o C, the reaction ratio of limeincreased by 19%, 10%, 10%, 8%, 6% and the reaction ratio of residue increseased by6%, 18%, 28%, 29%, 30% within 2 h, 3.5 h, 5 h, 7 h, 10 h.(2)The fineness of raw materials have obvious impact on the hydrothermal reaction ratio of residue-quartz and lime-quartz. With decreasing the remainder of 80 um sieve of quartz from 28% to 10.1%, the reaction ratio of lime increased by 3% and the reaction ratio of residue increased by 13%. The reaction ratio of residue increased by 7% when the remainder of 80 um sieve of residue was reduced from 33.4% to8.4%.4. The hydrothermal treatment of residue-quartz can be described by the Jander diffusion model, and the activation energy of the residue is 20.95 k J·mol-1 according to the Arrhenius equation.5. The hydrothermal sample of residue-quartz and lime-quartz was characterized by XRD. The results indicated that the hydration products of lime-quartz were mainly composed of calcium, quartz and hydrated calcium silicate gel in the early stage of hydrothermal treatment, dicalcium silicate, quartz and hydrated calcium silicate gel were main products in the system of residue-quartz at the same phase. When the hydrothermal time is more than 7 h, the hydration products of the two systems were well crystallized tobermorite and xonotlite. The hydration products of the two systems is the same and there are no new material when the value of C/S is 0.6 and 0.8,respectively. There was remanent calcium in the hydration products of lime-quartz when the value of C/S is 1.2. |
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