Sure you can. Here is a link to a T-shirt quilt I made. Look at the border. There is no sashing and T-shirt blocks were stitched together.
http://www.quiltingboard.com/picture...lt-t47094.html
What you must do is put an interfacing of some sort on your T-shirt knit fabric so it doesn't stretch out of shape. I use Pellon fusible interfacing, lightweight.