Concrete block construction requires a good mortar mix for adhesion. Mixing mortar properly adds strength to hold the blocks together when forming a wall. The same mortar mix can be used to hold together stones and bricks. Mortar mixed in the wrong proportions creates a weak link in the wall construction, which can lead to its failure. Concrete block mortar is like concrete mix, except it contains no aggregate or gravel.
Mix a single batch of mortar in the wheelbarrow. Add one rounded shovelful of Portland cement to four rounded shovels of concrete sand. For multiple batches, use the same ratio of 1 part Portland cement to 4 parts concrete sand. Substitute masonry cement for Portland cement if needed, using one shovelful of masonry cement for every three shovelsful of sand.
Combine and thoroughly mix the dry materials with the garden hoe.
Make a crater in the centre of the dry materials. Fill a coffee can full of water -- approximately 1 litre (1 quart). Pour one-third of the water into the crater. Mix the water into the dry materials with the garden hoe. Add more water, a little at a time, until the mixture is a thick paste.
Dip out a small amount of the mortar with the hand trowel. Turn the trowel upside down. If the mortar sticks to the trowel while it is upside down, it is of the right consistency.
The amount of water needed will vary, due to the moisture content of the sand. Use the mixed mortar within two hours after it's mixed. You can add approximately a half shovelful of lime for some flexibility in the mixture.