thats just sand with pebbles in it... if you are on about hard core, then you are looking at old smashed up bricks and stuff...

there is some stuff called "MOT" or something thats basically like sof limestone... you compact it down and it sets really hard... think they use it as part of the core foundation of most roads...

go to buildbase and try and talk to them... wicks is just a hypes up B&Q... they dont know loads, thye just sell it...