案情:2006年7月2日,某混凝土公司与某建设公司签订了《预拌混凝土购销合同》。该合同约定,由混凝土公司向建设公司承建的工程提供混凝土。供货时间为2006年4月至10月,并约定了标号和单价。同时约定,若建筑公司未按合同约定履行付款义务,应当自付款期限届满之日起向混凝土公司支付违约金,标 Case: July 2, 2006, a concrete company and a construction company signed a “ready-mixed concrete purchase and sale contract.” The contract stipulates that concrete be provided by a construction company contracted by a concrete company. Delivery time for April 2006 to October 2006, and agreed on the label and unit price. At the same time, if the construction company fails to perform its payment obligations as stipulated in the contract, it shall pay liquidated damages to the concrete company from the date of expiry of the payment term