Effect of ultrafine solid waste on the properties of ultrafine sulphoaluminate cement based grouting materials and its mechanism

WANG Pengfei; ZHANG Mingxuan; WANG Huixian; GAO Yinghui; YAN Pengyun; MA Yuchao

Abstract：To investigate the influence of ultrafine solid waste materials on the performance of ultrafine sulfoalumi-nate cement-based grouting material,a considerable amount of ultrafine solid waste fly ash was blended with ultrafine slag and ultrafine sulfoaluminate cement.The compressive strength,setting time,fluidity,water leakage rate and expan-sion rate of the grouting material were tested at the macro level.The hydration products were analyzed by X-ray dif-fraction analysis(XRD),Fourier infrared spectroscopy(FTIR),thermogravimetric analysis,and scanning electron mi-croscopy(SEM),and the effect of two types of ultrafine solid waste materials on the properties of ultrafine sulfoalumi-nate cement was described and the mechanism was analyzed from both macro and micro perspectives.The results dem-onstrated that:① On the basis of adding 20％-40％ultrafine fly ash into the ultrafine sulfoaluminate cement,0-20％ultrafine slag was incorporated.With the addition of ultrafine solid waste and mineral admixtures,the compressive strength of the composite grouting material at each age gradually declined.When the content of ultrafine fly ash was 20％,the 28 d compressive strength reached the maximum of 10.93 MPa.With the addition of ultrafine solid waste ma-terial,the reduction of the grouting materials in each fixed ultrafine fly ash content section was mainly attributed to di-lution,and the variations of setting time and fluidity were different.These two properties were mainly affected by the total proportion of ultrafine solid waste material.With the increase of the total proportion,the coagulation time initially decreased and then prolonged,and the fluidity initially decreased and then increased,reaching the extreme value when the total dosage was 40％.The initial and final coagulation time was approximately 40 min and 50 min,and the variation of the shortening and extension of the fluidity,which was about 200 mm,was caused by the combined action of the nucleation effect and dilution effect.When the condensation time was shortened,the nucleation effect was dominant,while the dilution effect was dominant when the condensation time was prolonged.The decrease in fluid-ity was mainly due to the high surface activity constraint of the ultrafine material.② Materials with a high content of ultrafine slag in terms of strength exhibited higher strength at the later stage due to pozzolanic activity.In terms of compressive strength,with the same content of ultrafine solid waste,grouting materials with a high proportion of ul-trafine slag had higher compressive strength at the later stage due to the pozzolanic activity of ultrafine slag.In terms of fluidity and condensation time,grouting materials with a high proportion of ultrafine slag had higher compressive strength.The proportion of different ultrafine mineral admixtures of solid waste had little influence on the grouting ma-terials.③ The variation in the amount of ultrafine solid waste material did not alter the type of hydration products,and the composite grouting material reacted rapidly within 1 day.In addition to the hydration products such as ettring-ite,monocarbon calcium carboaluminate was also generated.