Mixing pointing mortar involves combining sand, cement, and a plasticizer to create a workable and durable mixture for filling joints between bricks or stones. The exact proportions may vary based on the specific application.
Here's a breakdown of how to mix pointing mortar effectively:
1. Gather Your Materials:
- Building Sand (also called Pointing Sand): Provides bulk and workability. This is finer than sharp sand.
- Cement (Portland Cement): Acts as the binding agent.
- Plasticizer (Mortar Plasticizer): Improves workability, reduces cracking, and enhances water resistance. You can also use lime instead of a plasticizer.
- Clean Water: For hydration and achieving the correct consistency.
- Mixing Tools: Shovel, hawk, trowel, bucket or mortar tub, mixing board (optional).
- Safety Gear: Gloves, eye protection, dust mask.
2. Determine the Correct Mix Ratio:
- Standard Pointing Mix: A common starting point is 5 parts building sand to 1 part cement, plus plasticizer.
- Stronger Mix (for patios, exposed brickwork, or weak bricks): Reduce the sand content, such as 3 parts sand to 1 part cement, plus plasticizer. A stronger mix is generally not recommended unless absolutely needed.
- Lime Mortar (traditional): Ratios vary greatly depending on the lime used. A common one is 3 parts sand to 1 part lime putty.
3. Mixing Process (by hand):
- Dry Mixing: In a clean bucket or mortar tub, combine the sand and cement. Use a shovel to thoroughly mix the dry ingredients until you achieve a uniform color and consistency.
- Adding Plasticizer: Follow the manufacturer's instructions on the plasticizer packaging for the correct dosage. Add the plasticizer to a portion of the water you plan to use and mix well.
- Adding Water Gradually: Slowly add the water (with plasticizer) to the dry mixture, mixing continuously with the shovel. Add small amounts of water at a time to prevent the mortar from becoming too wet.
- Achieving the Correct Consistency: The mortar should be plastic and workable, similar to thick toothpaste. It should hold its shape on a trowel without being too stiff or too runny. If you squeeze a handful, it should form a ball that holds together but easily crumbles with pressure.
- Mixing Time: Mix thoroughly for at least 5-10 minutes to ensure all ingredients are well combined. This is crucial for proper hydration of the cement.
- Slaking Time (for lime mortar): Allow the mortar to stand (slake) for at least 30 minutes before use. Mix again before applying.
4. Tips for Successful Mixing:
- Use Clean Tools and Water: Contaminants can affect the strength and durability of the mortar.
- Mix Small Batches: Mortar will start to harden over time. Mix only the amount you can use within a reasonable timeframe (typically 1-2 hours, depending on temperature and humidity).
- Adjust for Weather Conditions: In hot weather, the mortar will dry out faster, so you may need to add a bit more water or work in the shade. In cold weather, the setting time will be longer.
- Consider a Mortar Mixer: For large projects, a mortar mixer can save time and effort.
- Avoid Overwatering: Too much water weakens the mortar and can cause it to shrink and crack as it dries.
5. Important Considerations:
- Mortar Color: If matching existing mortar, consider using colored mortar dye or carefully select sand that matches the original color.
- Brick/Stone Type: The strength of the mortar should be weaker than the surrounding brick or stone. Using a too-strong mortar mix can cause damage to the brick or stone over time.
- Professional Advice: For complex projects or historic buildings, consult with a qualified mason or building professional.
By following these steps, you can successfully mix pointing mortar for durable and aesthetically pleasing results.
