The whole idea seems strange to me. using a porous material like concrete or cenemt just screems Bacteria! Then there is the whole leeching of chemicals into the finished product. Ok so you line it with something.... well if you tile it there will be grout lines (see the first 2 issues). So you...
I was always told that the bigger cause of aphids is ants. Because the ants actualy milk the aphids for food. I dont know this to be true but usually when I have an aphid issue on my roses i can usualy find ants nearby. When i attack both(usually in spring) I dont seem to have an issue the rest...