In all cases where any public authority fixes a prevailing rate of wages under section 4115.04 of the Revised Code, and the work is done by contract, the contract executed between the public authority and the successful bidder shall contain a provision requiring the successful bidder and all his subcontractors to pay a rate of wages which shall not be less than the rate of wages so fixed. The successful bidder and all his subcontractors shall comply strictly with the wage provisions of the contract.
Where a public authority constructs a public improvement with its own forces, such public authority shall pay a rate of wages which shall not be less than the rate of wages fixed as provided in section 4115.04 of the Revised Code, except in those instances provided for in sections 723.52, 5517.02, 5575.01, and 5543.19 of the Revised Code.