Concrete blocks with two or more cells (cavities) comprising more than 30% of the volume, which may be grouted and reinforced.

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Hollow concrete blocks, Peru (S. Brzev)

Hollow Concrete Blocks 1.JPG

 

 

 

 

 

 

 

 

Hollow concrete blocks with three cells, Haïti (front) and with two cells, Canada (rear), (S. Brzev)