Abstract: In order to improve the sealing quality of gas extraction borehole in coal mines,a kind of new hole sealing material was developed with calcium sulphoaluminate,lime and gypsum as main components.The effects of SDS on properties such as setting time and strength were measured.The morphology of reaction product was observed with a scanning electron microscope(SEM).The chemical effect mechanism of SDS on sealing material was probed by measuring the ions concentration in the slurry filter liquor among others.The results show that after addition of SDS,the surface tension of the slurry decreases,and the setting time shortens,and the swelling stress increases,and the uniaxial compressive strength increases slightly at 6 and 24 hours but decreases significantly after 3 days.SDS accelerates hydration reaction of the material in early stages and leads to a smaller crystal size of hydration product,and SDS affects properties of the material via introducing .The physical function of drawing air bubble into the slurry and increasing the [OH^-] and Al content in the liquid phase of the slurry.

Key words: sodium dodecyl sulfate (SDS), sealing material, setting time, strength, swelling stress