From time to time, as the work under any contract for such an improvement progresses, upon certificates by the Committee or by some officer designated by the Committee for that purpose, payment may be made either in money, vouchers or bonds as provided for in this Division, to apply upon the contract price, reserving, however, a sufficient amount upon each of the payments to properly secure, in the judgment of the Committee, the faithful performance of the contract. This reserve shall be paid over at such time and on such conditions as the Committee shall fix, after the specified work has been completed or accepted.
55 ILCS 5/5-32056