In the recent coverage of the civil war in Syria and just this past few weeks, the bombings in Gaza City, one is struck by the sheer amount of concrete and rebar left in great tumbled piles. No trees, no wood, no parks or lawns, Palestinian refugee camps and Gaza itself are dense concrete worlds.
North Africa and the Middle East sit on a shield of limestone, interleaved with layers of sandstone. It is all made clear in a really interesting paper on the significance of reef limestones. Calcareous limestone: fossils and shells, sand from the edges of the ocean, oil from the animals and vegetation that lived there: it is geology itself that produces the wealth, the tensions and the landscapes of the Middle East, and has for a long time: the pyramids are sandstone blocks, faced with limestone sheets. Photographs of Palestine in the 1920s show a sandstone architecture, however, quarrying and building in stone is not the process for quick reconstruction in war, concrete clearly is.
Concrete debris can be re-used as aggregate: it isn't as strong, but there is lots of it. All the steel reinforcing bars and mesh can be hammered out and re-used, and concrete can always be mixed in small batches, by hand if necessary. Not that the entire Gaza Strip is in rubble; there are concrete companies with perky websites just as there are anywhere else.
The Israeli blockade of Gaza allows the entry of construction materials from Egypt only for Palestinian Authority projects. As the PA does not operate in Gaza, Hamas does, the list is effectively embargoed. Nonetheless, the territory sits on limestone, abuts an ocean full of sand, and is provided with rubble of all kinds on a regular basis.