The knockability of modified silicate sand was researched. Heating specification and cooling ways for measuring residual strength of silicate sand specimens were mapped. Knockability of 18# modified silicate sand was evaluated by means of residual strength value less than 0.5 MPa as a criterion. The results show that the CO2 modified silicate sand exhibits acceptable knockability with 2.5%

4

.0% binder addition at 400

1

000 ℃. Residual strengths of common and modified silicate sand are measured at 200

600

800

1 000

1 200 ℃. It is found that peak residual strength appeared at 800 ℃ in both common silicate sand and modified silicate sand A1

and valley value appeared at 800 ℃ in both 18# modified silicate sand and modified silicate sand B2. The forming mechanism was approached.