Skilled workers are now pumping a filler substance into the "tubular" voids created by the alignment of the blocks and the matching-up of their "half-pipe" coves on all four sides. It appears to be a cement-like compound, mixed in small batches and forced in with a hand pump and hose assembly. In other images the effect can be seen as wetness where the blocks meet.

So now we have the blocks laid out and stabilized with a mastic, organized with horizontal and vertical re-bar, and solidified with a dose of cement-like filler. The wall pairs are also connected with custom-made metal spacers to maintain precisely parallel structures.

These walls will not come a-tumblin' down! See more here.