It has been recommended that we use a 5-inch pipeline to pump 4inch slump concrete made with 1-inch top size expanded shale aggregate. We had always thought that the line diameter only had to be four times the top size of the aggregate. We have trouble with laborers if we require them to handle anything bigger than 4-inch pipe. Isn't 4-inch big enough?
If you are pumping any substantial distance the larger size is much safer to use with such large lightweight aggregate. The headaches of plugged lines are likely to be worse than those of dealing with the work force. We suggest that you do what you can to facilitate the ease of handling the large line and stick with it.