Any contract may provide for progressive payments, if in the ordinance authorizing or ordering the work permission is given for such a contract. But no progressive payments can be provided for or made at any time which, with prior payments, if there have been such, shall exceed in amount at that time ninety percent of the value of the labor done and the materials used up to that time, and no contract shall provide for or authorize or permit the payment of more than ninety percent of the contract price before the completion of the work done under said contract and the acceptance thereof by the proper officer, department or board.