Abstract: In order to improve the fire resistance of cement wallboard structure, nano materials which are micro silicon powder and carbon fiber were used as admixture to study the material modification. Test pieces were prepared with the mass ratio of standard sand and Portland cement of 2∶1. The compressive strength, flexural strength, fire resistance and dry shrinkage were tested and the micro morphology was analyzed. The results showed that micro silicon powder and carbon fiber can not only improve the compressive and flexural strength of cement masonry, but also improve its fire resistance. The cement wallboard with double addition of micro silicon powder and carbon fiber content of 3% and 2% has the best fire resistance, and the mass loss after combustion test is 0.64%, 85% lower than that of the reference group. It is found by micro morphology of cement based modified materials that the filling effect of ultrafine silica powder particles is the main reason for the improvement of material strength performance, and the bonding effect and surface reaction of carbon fiber are the main reasons for the improvement of fire-resistance performance.

Key words: micro silicon powder, carbon fiber, cement wallboard, strength test, fire resistance, SEM