Sand is a very important element in bricklaying as far as a mortar mix is concerned. Generally, the quality of the sand is the major factor determining the quality of a plaster mix or mortar mix. It’s recommended that the sand should have enough ‘fines’ (- 75 micron material) to get a good plastic mix with a water content that’s less than 350 litres/m3. Generally, a mortar mix or plaster mix is made within the range of one bag of cement to 200 to 300 litres of damp sand.
Apart from experience the next best indicator of the quality of sand is a field test. In other words, if you do not have the required training or experience in bricklaying, the best bet to determine the amount of sand for a good quality mix is by carrying out a field test. Let’s have a look!
• Get about 50kg of sand and air dry it.
• Scoop 25kg of the sand, 5 kg of cement as well as litres of water ( with 1 litre and 1.5 litres of the water in different containers).
• Mix the cement and sand to form a smooth, uniform and consistent colour.
• One after the other, mix the the sand - cement mixture in the three quantities of water. Do this until you’re able to achieve a mix that’s workable enough to use as plaster.
With that done, you should take note that if 5 litres of water is sufficient then the quality and quantity of the sand is perfect. If you’d require 6 litres of water to get a mix workable as a plaster, then both the quality and quantity of the sand is average. However, if you’d need 7 litres of water to get a mix workable as a plaster, then the quality of the sand is poor. Any requirement of water above 7 litres implies a very poor quality of sand.