Selling the process of pumping is a matter of selling economics to the contractor and quality to the specifier. The good economies of pumping have probably accounted for most of its growth., but the high quality of properly pumped concrete is probably not so well known, and for future growth into that part of the market that has not yet been penetrated it is important to sell quality. And here the question that must be met head on is, "is it necessary or is it even common practice to put soup into the pump receiving hopper?" It can be reasonably argued that we can modify the concrete to suit the needs of the conveying system so long as we do not harm the quality of the concrete. Quality of concrete relevant to both strength and durability is expressed in terms of water-cement ratio and air content. In a given situation, a water-cement ratio of .5 may be needed. It is possible to achieve this with concrete having a slump of one-half inch and also with concrete having a slump of seven inches. Again it is possible to achieve it in concrete with 30 percent sand as surely as in concrete with 60 percent sand, or in concrete with any maximum aggregate size. The concrete with high slump, high sand and smallest aggregate size is the most expensive but its quality as we have defined it is no better or no worse than the others. Overall economy will be achieved if the cost saving in the conveying system exceeds the premium for a more expensive concrete. By one means or another, it is undoubtedly possible to produce pumpable concrete of any desired quality. It is also possible to construct a logical argument that overall job economy permits a considerable amount of tampering with the concrete mix design. Yet the industry ought not to lean too heavily on this argument lest it reinforce the allegation that soup is commonly put into the receiving hopper. Even though the soup may have the correct water cement ratio it may not help public relations with technical people who associate wet mixes with low strengths. This country lags behind all the highly developed countries of the world and some of the underdeveloped countries in the per capita use of concrete. This is so because we have always had an abundance of alternative construction materials available. In the new period when everything seems in short supply, we are merely being introduced to a situation well known to the rest of the world. Anyone who reduces the cost of concrete ensures a bright future.
