we are chinese manufacturer specilizing in supplying microsilica. we can offer silica of refactory and cement degree. Generally we can provide you with SIO2 85%--90% microsilica which complys to ASTM C 1240 standard .it is a very fine pozzolanic material, composed of amorphous silica produced  byelectric arc furnaces as a byproduct of the production of elemental silicon  or ferro silicon alloys.Silicafume can be used in a variety of cementitious products such as concrete,grouts,and mortars as well as elastomer,  polymer,refractory, ceramic and rubber applications.