Mortar is a simple recipe of prepackaged mortar mix, dry sand and water but you're likely to end up frustrated if the quantities of each ingredient are off. When mixing water for concrete blocks an old rule of thumb says to use 2 1/2 bags of mortar mix and 272kg. of sand for every 100 concrete blocks. Professional bricklayers know that mortar has a sweet spot when it comes to water -- add too much or too little and you'll end up with an unworkable product. You can use a simple procedure, called the "slump test," to determine when you've added enough water to your mortar mix.
Pour the mortar mix and sand into the wheelbarrow. Many bags of sand make up 272kg. so it's unlikely you'll be able to mix all your mortar at one time. Start with three 22.7kg. bags of sand and 5/8 bag of mortar mix.
Use a garden hoe to thoroughly mix the ingredients.
Slowly pour water into the wheelbarrow as you continue to mix the materials.
Stop adding water when the mixture has the consistency of oatmeal or slightly melted ice cream. Fill a paper cup with the bottom removed with the mortar mix to test its texture. Lift the cup straight up, sliding it off the mortar. If it holds its shape, move onto the next step. If it's too watery, add sand until the proper consistency is achieved.
Begin using immediately. Mortar mix dries quickly.
Buying all sand and mortar mix at the same time will ensure that you don't end up with different-coloured mortar when it dries.
Wear gloves and avoid getting the mortar mix on your skin. Mortar mix contains caustic agents that can cause burns. Don't mix more mortar than you can use in about two hours.