I am inspired by this video. In the video, the person blends some pasta and adds water, and the result looks like dough. Can it be used as bread or pizza dough?
Not exactly. Pasta is made from bits of wheat that are not flour or bran - otherwise known as semolina. Assuming that the pasta hasn't gone through very much more than drying as processing, you're going to end up with something fundamentally different from the grade of white flour - whether its type 00, or other kind of white flour.
You would get a dough, but something fundamentally different from just adding water to regular white flour, and it would likely have a very different taste and texture from regular flour.
No, you can't. And the problem is not the semolina - semolina is a somewhat rougher milling grade of flour, not a different part of the kernel. Also, much pasta is made with flour, not semolina.
The problem is, as frequently in cooking and baking, what matters is the microstructure of your result, and the same list of ingredients mixed in different ways gives you different microstructures. In this specific case, you make dough by hydrating the starch and allowing the glutenin and gliadin proteins in the flour to combine in the presence of water and make gluten. You also add yeast which gets trapped between the gluten and makes gas bubbles when fermenting.
Freshly made, well hydrated gluten is like a rubbery mesh. When you dry it out, as in making pasta, it stiffens. When you destroy it with a blender, to make powdered pasta, you end up with fractured pieces of your gluten structure. Rehydrating it will not build it up again. So, no, the mixture you produce will not be a dough, and won't build up into a pizza or bread.
You can definitely make pizza with durum wheat (aka semolina). And you can make bread as well (see for instance http://www.breadworld.com/recipes/Artisan-Semolina-Bread- ). Pizza with semolina is not unheard of and you can find it in Italy (not common, but it is possible to find it)
To be very general. What you need to make pizza dough (or any rising dough) is something with starch (any kind of flour, otherwise yeast won't grow) and gluten (otherwise pizza will not rise in the oven). Semolina has both (while, for instance, rice flour has not gluten...)
I am not sure that blending pasta is the best way to do that, but I do not see any reason why that should not work (pasta is just semolina + water).