There is no beam in the middle of 8 m X8 m cast-in-place concrete. If there is, how many steel bars should be provided?

Are you talking about 8m*8m cement board? According to general experience, the plate thickness is 8000/35, which is 230 mm, the minimum reinforcement ratio is 230* 1000*0.002=460mm2, and the spacing is 200 mm 12mm ... but the actual calculation shall prevail. For such a large span, it is not cost-effective not to set beams.