The description for Accordion Wire doesn't state how much of an area you can cover with it, or how one can use things like wire cutters or explosives to clear it. It also doesn't seem to give any guidelines for how long it would take to deploy it. Most of the time it wouldn't matter, but when you have an attack incoming and you need to toss up an improvised defense, every moment counts. Time to remove is even more important, given that you are probably going to be shooting at those doing it, or being shot at by those who don't want it removed.
I'm assuming that Accordion Wire is the 40k name for Concertina Wire. There is some details about the stuff there. One relevant section is - A barrier known as a triple concertina wire fence consists of two parallel concertinas joined by twists of wire and topped by a third concertina similarly attached. The result was an extremely effective barrier with many of the desirable properties of a random entanglement. A triple concertina fence could be deployed very quickly: it is possible for a party of five men to deploy 50 yards (46 m) of triple concertina fence in just fifteen minutes. Optionally, triple concertina fence could be strengthened with uprights, but this increases the construction time significantly.
Based on the numbers I've been able to find, it looks like half a kilo of Barbed Wire would be between 3 and 10 meters long.