Preparation Of Hydrated Magnesium Silicate Cement With High Activity Magnesium Oxide

Hydrated magnesium silicate cement has the characteristics of light weight,low alkali,good surface gloss,etc.,which has certain potential value in the field of sealing nuclear waste and building materials,and belongs to a new type of green building material.In recent years,hydration mechanism and physical properties of hydrated MgO-Si O₂-H₂O system have been studied a lot,but for the whole MgO-Si O₂-H₂O system,these studies are still in the primary stage.In this paper,the performance of hydrated magnesium silicate cement prepared by high activity MgO was tested,including:the influence of active MgO raw materials on M-S-H;the corrosion resistance of hydrated magnesium silicate cement;the influence of metakaolin on the hydrated magnesium silicate cement system.Combined with the microscopic results of the test and with the help of a variety of micro detection methods,the mechanism of the above effects on hydrated magnesium silicate cement is explored.The main results are as follows:（1）M-S-H can be prepared from light burned magnesia with 50%-80%activity.The preparation of hydrated magnesium silicate cement by calcining magnesia from magnesite tailings can not only reasonably apply the high activity light burned magnesia,but also save the cost.At the same time,the performance of hydrated magnesium silicate cement is good.Comprehensive analysis shows that the compressive strength of hydrated magnesium silicate prepared with active MgO content of 71.06%can reach 48.5MPa in 28d;the samples prepared with MgO activity less than 71.06%show strength inversion phenomenon in 28d,which is due to the fact that there is still residual MgO in the system after curing for 28 days,and Mg（OH）₂harmful to the system is generated by continuous hydration in the system,which leads to the decrease of system strength.Therefore,70%～75%MgO activity is suitable for the preparation of hydrated magnesium silicate cement.（2）The strength retention coefficients of 1.9%Na Cl and 3%Na₂SO₄were 0.94and 0.83,respectively.The reason was that M-S-H was mainly layered structure,and the macroporous structure was mainly composed of gel pores smaller than 10nm,and the structure was dense.（3）The results show that the addition of less than 10%metakaolin can improve the 28d compressive strength of magnesium silicate hydrate,and the compressive strength of 8%metakaolin increases by 60.9%;FT-IR shows that Al₂O₃in metakaolin participates in the reaction,and the increase of metakaolin content will cause the change of microstructure;the introduction of metakaolin will lead to the increase of hydration degree of the system,and the hydration degree of 8%metakaolin is the largest The results showed that the weight loss of TG was 3.08%higher than that of the blank group;metakaolin could increase the p H value of the system,and with the increase of the content of silica fume,the amount of M-S-H was affected.（4）The hydrated magnesium silicate cement was prepared into anti-static floor,and its load and standard resistance were tested.The results show that the anti-static floor made of hydrated magnesium silicate cement can reach the standard,which indicates that the new cementing material,magnesium silicate cement,can be applied in the field of building materials.