首页|Preparation of Low Ratio Magnesium Ccement by Acid Leaching Treatment of Boron Mud
Preparation of Low Ratio Magnesium Ccement by Acid Leaching Treatment of Boron Mud
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The effects of liquid-solid ratio and reaction time on the leaching rate of magnesium at room temperature were investigated,as well as the effects of the molar ratio of MgO/MgCl2,the amount of water added,and the amount of acid-impregnated slag dosed on the compressive strength and water resistance of LR-MOC.The results showed that the magnesium element in the boron mud could be maximally leached under the conditions of 1:1 concentration of hydrochloric acid at room temperature,liquid-solid ratio of 2.5 mL·g-1,and reaction time of 5 h,and the main products were amorphous SiO2 as well as a small amount of magnesium olivine which had not been completely reacted.The LR-MOC prepared using the acid-soaked mixture could reach a softening coefficient of 0.85 for 28 d of water immersion when the molar ratio of MgO/MgCl2 was 2.2,the amount of water added was 0 g,and the acid-soaked slag dosing was 40 wt%,which also led to an appreciable late-strength,with an increase of 19.4%in compressive strength at 28 d compared to that at 7 d.Unlike previous studies,LR-MOC prepared in this way has a final strength phase that is not the more easily hydrolysed 3-phase but the lath-like 5-phase.For this phenomenon,we analyzed the mechanism and found that,during the acid leaching process,a part of amorphous SiO2 dissolved in the acid leaching solution formed a silica sol,in which Mg2+played a bridging role to make the silica sol more stable.With the addition and hydrolysis of MgO,the silica sol gel coagulation slows down,providing a capping layer to inhibit the hydrolysis of the 5-phase crystals and providing some strength after coagulation.The amorphous SiO2 in the other part of the acid-impregnated slag generated M-S-H gel with Mg2+and OH-,which synergised with the dense structure composed of interlocking crystals to improve the water resistance of LR-MOC.
boron mudmagnesium chloride-oxygen cementacid immersionwater resistancesilica sol
YANG Mei、ZHANG Mingzhe、CHEN Hao
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School of Materials Science and Engineering,Shenyang Jianzhu University,Shenyang 110168,China
School of Physical Science and Technology,Shenyang Normal University,Shenyang 110168,China
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