Hollow blocks are concrete blocks with hollow centers tailor designed with an objective to reduce weight. High density blocks can be produced by a combination of cement, sand and fine gravel, while low density blocks are produced by using fly ash as an alternative for the aggregate.
Structural performance of the walls is achieved when reinforcement bars are used either horizontally or vertically inside the blocks.
Ungrouted, partially grouted or grouted walls are the different structural reinforcements possible with these blocks. The grouted walls, being the most structurally strong type finds its application in seismic zones.