Masonry bricks/blocks should be joined with a mortar which is relatively weaker than the mix used for making blocks in order to avoid the formation of cracks.

A rich mortar (strong) tends to make a wall too inflexible/rigid thus limiting the effects of minor movements due to temperature and moisture variations resulting in cracking of the bricks/blocks.

We advice you to use a motor of either 1:5 or 1:6 proportions (cement:sand) for masonry bedding.