What is the weight of a square foot in concrete?

A square foot of concrete has no weight because a square foot has no thickness.

A cubic foot of concrete would weigh 65 Kg (143 lb)

If you ASSUMED that concrete driveways, paths, etc. are all the same thickness , which they are NOT, then let us say they are 4 inch thick (10cm) In that case, then 1Square Ft of Concrete would weigh one third of the figure given above. Therefore it weighs 48 lb which is the same as 22 Kg.. Density of Concrete is 34.4 gram per cubic Inch or 1.216 ounce per cubic inch. (since you seem to be wanting to use Imperial measure)