Study On The Influence Of High Temperature On The Structure And Properties Of High Aluminum Cement

In recent years,due to the limitations of resources and the environment,China's refractory binders have gradually developed in the direction of high quality,high performance and high construction performance.This is also an inevitable trend in the development of the refractory industry.Good performance and other advantages,it is a durable and environmentally friendly refractory material.However,many scholars have found that high alumina cement will reduce the strength of high alumina cement products due to the crystalline transformation of hydration products.Changes will also occur,and these two points have always restricted their development.In this paper,reburned MgO powder and activated Al₂O₃ powder are used as admixtures to determine the macro and micro properties of high alumina cement stones with different water-cement ratios under the conditions of different proportions of magnesium powder and aluminum powder.Changes in morphology,changes in volume,changes in compressive strength,changes in micro-morphology,and hydration products.Micro-tests were performed using SEM,XRD and other technical methods to analyze the mechanism of action.After analysis,the conclusion was drawn:At different temperatures,as the water-cement ratio changes from 0.15 to 0.25,the volume of high-alumina cement stones first decreases and then becomes larger as the water-cement ratio increases.At different temperatures,as the MgO content changes from 0 to At 10%,the volume becomes smaller and then becomes larger at 600?.At other temperatures,the volume decreases as the MgO content increases;at different temperatures,as the Al₂O₃ content changes from 0 to 20%,the volume of cement stone Both decrease with increasing Al₂O₃ content;The addition of MgO and Al₂O₃ is beneficial to improve the volume stability of high alumina cement.The best mixing ratio of volume stability is water-cement ratio 0.2,the content of MgO is 10%,and the content of Al₂O₃ is 20%.During the temperature rise from normal temperature to 1200?,the volume of high alumina cement stone test block first increased and then decreased with the increase of temperature.The volume change reached the maximum at 1200?,and the volume expanded 4.10%compared with normal temperature at 900?.Good volume stability in the following temperature ranges;At different temperatures,as the water-cement ratio changes from 0.15 to 0.25,the strength of high alumina cement stones decreases as the water-cement ratio increases;at different temperatures,as the MgO content changes from 0 to 10%,At normal temperature,the strength increases with the increase of MgO content,and at other temperatures,the strength decreases with the increase of MgO content.At different temperatures,as the Al₂O₃ content changes from 0 to 20%,the strength at room temperature varies As the Al₂O₃ content increases,it decreases first and then increases.At other temperatures,the strength of the cement stone decreases as the Al₂O₃ content increases.Addition of Al₂O₃ has no obvious effect on the strength of high alumina cement.The best mix ratio of strength is water-cement ratio 0.15,MgO content 5%,Al₂O₃ content 0%.Under this mix ratio,the temperature rises from normal temperature.In the process up to 1200,the strength of the high alumina cement stone test block increases first and then decreases with increasing temperature.The strength reaches the maximum at 600?,and the strength performance is better in the temperature range below 900?;The hydrated products of high alumina cement stone test blocks with different mixing ratios have C₂AS and C₃ A at high temperature.The test blocks with 10%MgO content and 20% Al₂O₃ content are calcined to 1200?,and Mg Al₂O₄ is produced.In terms of microstructure,there are more pores inside the test block after high temperature calcination due to the loss of crystal water.The addition of MgO and Al₂O₃ .It can promote the formation of C₂AS and make up for the pores caused by the loss of crystal water.