i made this much of the 16 concrete types in chromatic order (starting from white)
4559, 969, 1225, 4545, 1819, 5569, 3079, 4931, 2671, 3137, 5935, 4363, 7287, 1863, 2277, 2533
light blue and orange are underestimated by 100-200 each because there are still some blocks of those color in the blast chamber pipeline. but adding this all up, it turns out that from 18 double chests of sand and gravel, i got 16.5 double chests of concrete -- i assume the rest was lost from imperfections in the blast chamber, transport system, and sorter, and from when i was still experimenting with the system. 90% recovery rate is lower than i was expecting, but not catastrophically bad.