(a) A ready-mixed concrete truck may be operated on a public highway of this state only if the tandem axle weight is not heavier than 46,000 pounds and the single axle weight is not heavier than 23,000 pounds.
(b) A truck may be operated at a weight that exceeds the maximum single axle or tandem axle weight limitation by not more than 10 percent if the gross weight is not heavier than 69,000 pounds and the department has issued a permit that authorizes the operation of the vehicle under Section 623.0171.