Equipment improvement and the growth of experimental and field knowledge regarding the pumping of concrete have been progressing so rapidly that a serious information lag has developed. In an attempt to bridge this gulf, the American Concrete Institute and the Delaware Valley ACI Chapter joined forces to conduct a Concrete Seminar in Philadelphia. When should concrete be pumped? In evaluation a transporting method, the foregoing two sets of factors, mix design and job conditions, should be the determinants. Pumping is commonly used for the following applications: where accessibility is a problem; when space on the jobsite is at a premium; when large amounts of concrete are needed within a short time (conveyors are also a good choice for high rates of delivery); where obstacles intrude between the point of concrete delivery and the desired point of final placement; where traffic between the delivery point and deposit area is impossible or not desired; for use in placing concrete in relatively inaccessible spots; and wherever the other methods of transporting would not be practical. It should be kept in mind that with today's pumps the maximum effective pumping distance is up to 1,000 feet horizontally and up to 300 feet vertically, although concrete has been pumped longer distances successfully. Should alterations of the mix design be permitted to improve pumpability? The rule used to be: "Select the transporting method to suit the concrete- don't change the concrete to suit the transporting method." Progress in pumping equipment design has been so rapid in recent years that it is possible to pump mixes today that just a few years ago would have been considered unpumpable. Even so there are some concretes that cannot be pumped with the required reliability. Does the engineer, architect, or owner then permit a redesign of the mix or change in materials to render the concrete pumpable? This depends on several factors. In some cases, the answer is a flat no because some specifications prohibit such changes. What features should be sought in a pump? The best way to judge a pump is by using it. If possible, rent pumps of the types you are considering and use them in pumping a number of different concrete mixes under a number of different job conditions. Look for: the pressure the equipment is capable of developing; maximum hourly concrete capacity; and capacity of the storage hopper.