Study On The Effect Of Hydration Of MgO In Steel Slag And The Effect Of Hot Tantalum On The Hydration Characteristics Of Steel Slag

In this paper,firstly,f-MgO was prepared by simulated calcination experiments,and the effect of fineness on the hydration and expansion properties of f-MgO prepared by simulated calcination was studied.Then,the steel slag(SS)was modified by pressure steaming,and the expansion and hydration properties of the modified SS were explored,and the reasonable and effective modification process of the SS was explored.At last,the modification experiment of SS with silicon material was carried out,and the influence of siliceous material on the expansion and hydration of modified SS was studied.The optimum modification process of SS was clarified,which provided theoretical guidance for the practical application of SS.High-temperature calcination inhibits the hydration and volumetric expansion of f-MgO,increases the fineness of f-MgO,which can significantly improve its hydration and volume expansion properties;Under the maintenance regime of 20 ℃,the hydration reaction capacity of f-MgO was weak,and the volume expansion performance was smaller;The blended cement pastes with MgO samples still had a tendency of expansion after curing for 360 d.Under the condition of curing at 60 ℃,when the MgO particle size is small(DSO=9 nm),the volume expansion rate of the samples will gradually become stable after curing for 28 d,but when the particle size of MgO is larger(D50=120 nm),the expansion rate of the samples rapidly developed and finally fractured;Increasing the fineness of f-MgO can increase the heat release rate of hydration,and the total heat release will also increase;After MgO is incorporated into cement,MgO reduces the heat release rate and total heat release of cement;The smaller the degree of refinement with MgO,the greater the decrease;the morphology of the hydration products of MgO in the cement paste is irregular and mostly filled in the holes.After the SS is pressure-steam modified,its expansion performance is effectively controlled;f-CaO in the SS is more sensitive to the high temperature and high pressure environment,and It can be quickly hydrated by pressure-steaming under 0.2 MPa for 30 min.,while f-MgO is more stable;under the condition that SS replaces 30%of cement,the modified SS will reduce the heat of hydration of the blended cement pastes with SS samples,and with the increase in pressure and temperature,the heat of hydration of the sample decreases gradually;After the SS is pressure-steam modified,the gelling of SS activity has a certain negative effect,compared with the unmodified SS samples,the mechanical properties of the modified SS samples are reduced to varying degrees;SEM show that the modified SS samples has a loose structure and contains more holes and micro-cracks.After the SS was modified by pressure-steaming with siliceous materials,the content of its hydrated and expansion phase was significantly reduced,and the pressurization stability was satisfactory;After the SS was treated by autoclaved modification,the Ca(OH)2 in the modified SS reacted with the silicon material,and CSH gel was generated;The CSH gel can stimulate the hydration of modified SS samples and improve the mechanical properties of the samples;In addition,the hydration dormant period of the modified SS samples is shorter,and the second exothermic peak appeared earlier,moreover,the heat of hydration is lower;When the content of siliceous material exceeds 5%,the siliceous material in the modified SS exists in an "excessive" state,This part of the"excessive" siliceous material will be hydrated with the Ca(OH)2,which hydration by the blended cement pastes with modified SS.The"pozzolanic reaction" can also improve the mechanical properties of the samples,but due to the low chemical reactivity of siliceous materials,in a short time,the "pozzolanic reaction" has little effect on the mechanical properties of the specimen after adding more than 20%;SEM show that the composite samples with modified SS has a dense structure,disordered growth of various types of hydration products,mutual stacking,fewer holes,and low porosity.Comprehensive conditions such as external costs,it is recommended to select pressure steaming conditions for the 0.2 MPa-30 min,siliceous material content of 20%of the modification process.