When you’re just starting with bricklaying, you probably won’t know how to prepare a mortar. There’s nothing to worry about since even seasoned professionals find it challenging at times.
But a builder needs to get the proportion right. It would ensure uniformity of strength throughout the building structure, uniform workability, and uniform colour.
If you’re looking for guidance on the correct brick mortar mix ratio, then here’s a thorough guide for you. Irrespective of whether you’re a beginner or experienced professional, you’ll find it useful.
What is Mortar?
A mortar is a paste that combines cementing material with fine aggregates. The material is commonly cement, but it can also be lime at times.
And the entirety is sand, but can also be sawdust, surki, or a combination of the three. It is mixed with water in an as-needed proportion. Mortar is used as a binding agent that binds bricks and stones.
Types of Mortar
You must know that there are different types of mortar. The proportion you take will depend on the type of mortar you’re preparing. Those are:
- Type N mortar
- Type M mortar
- Type S mortar
- Type O mortar
The most common type of mortar is Type N. This general-purpose mortar allows for better workability and elasticity. Thus, it prevents cracks and spalling of adjacent bricks.
You’d use them for above-grade walls where the compressive strength is about 750 PSI. Besides being used for setting bricks, Type N mortar also finds its application in repointing newer bricks.
Type M is less-commonly used, but it offers the highest compression strength of 2500 PSI. You’d use this mortar type in places where the structure has to deal with high gravity or lateral load.
For projects that require hard stones, M Type mortar can bind them together with greater efficiency. Type S mortar is somewhere in the middle with a medium compression strength requirement of 1800 PSI.
You’ll be using them for below-grade walls. The bonding strength is more remarkable for Type S than Type N., And because of more lime content, these mortar can withstand excess moisture and are elastic.
The final mortar type, Type O, is used when the compression strength requirement is low or not a factor. You only get about 350 PSI of strength. But it’s also easy to work with and offers a consistent blend.
You’ll be using Type O primarily for soft stone applications. There are other scientifically modified and blended mortar types available. But it would help if you got the job done with the above four types.
Sand to Cement Ratio
Now the main question is at what ratio should you combine the materials to prepare the mortar. Many people are concerned about the sand to cement ratio. But it would be best if you were concerned about the cement, sand, and hydrated lime ratio.
For general purpose tasks, you should mix six portions of sand with one portion of Portland cement. For projects that require greater strength, you need to increase the cement part and mix four sand bits with one portion of cement.
So this would depend on the type of structure you’re working on. For a specific type of mortar, you need to mix cement, sand, and hydrated lime in the following ratios:
- Type M – 3:12:1
- Type S – 2:9:1
- Type N – 1:6:1
- Type O – 1:9:2
To prepare Type M mortar, you need to mix three parts of Portland cement with 12 parts and 1 part hydrated lime. The reason for including hydrated lime is because it helps retain more water than cement.
When preparing mortar, you do not generally consider water proportion. It depends on how much moisture you want in your mortar.
Mortar Mix Procedure
To prepare mortar, here’s a step-by-step procedure you can follow:
- Take a dry bucket and measure the proportion for each material. Maintain as much accuracy as you can.
- Wash the mortar container and pre-wet it before pouring in the materials.
- If you’re mixing by hand, then take a flat and tall container.
- Add all the materials in correct proportion and mix them before you add water.
- Now add in the water gradually until you reach the desired moisture level.
- Keep mixing until the water is thoroughly mixed with the materials. You must mix until you reach a smooth consistency.
- When the mortar becomes wet enough that it slips off the shovel, stop mixing.
Now you have the mortar ready for use. To check for viscosity, make few ledges, and if they stand tall, you have prepared it correctly.
Things to Note for Mortar Mix Proportion
When preparing the mortar, there are few things to keep in mind.
- Always use fresh cement that is unopened. Open cement tends to take up moisture which affects the water content in mortar mix.
- The mortar remains suitable for 90 minutes from preparing. After this, some of the properties start to deteriorate.
- Weather plays a critical role in how the mortar reacts. It also determines its efficiency and for how long you can manage it in the open. So have your plans in place.
- You’d most likely be preparing multiple batches of mortar. It’s crucial to maintain consistency for each batch. Use the same materials and the same brand for better accuracy.
- Irrespective of whether you’re using a mixer or tub, you should introduce the next batch no later than five minutes after the last batch.
- If you find the mortar is drying up, then add water to maintain the moisture. Do not apply the dry mortar.
- Ensure the sand is of a finer grade. There should be no clay or other contaminants that would affect the mortar consistency.
- Safety comes first. Therefore, always use eye protection, gloves, and aprons.
To Sum up
After you prepare the mortar 7-10 times on your own, you’ll be more confident when preparing the mortar. You’ll gauge the water content and weather conditions better.
It’s always essential to maintain the ratio for each mortar type. If you find any inconsistency, it’s better to seek guidance rather than move ahead with the prepared mortar. In constructions, there is usually very little room for error.