Mix Portland Mortar
Portland cement mortar, simply known as cement mortar, is a mixture of Portland cement, sand, and water (plus additives, if any). It is the most common mixture used today for making mortar, a workable paste that is used to set blocks and bricks. Cement mortar must be mixed just before use so that it does not cure prematurely. For this reason, it is beneficial to learn how to mix Portland mortar yourself. The process is fairly straightforward and requires only a few tools and supplies.
Steps
- Purchase the materials that you will need. Portland cement is a dry powder and can be purchased at most hardware stores and building supply stores. The water can come straight from your spigot at home. When buying sand, make sure to buy sand with angular (rather than smooth) grains. Masonry sand is ideal, and can be purchased from most building supply stores. Additives are available at most home improvement centers and building supply stores. Make sure to read the directions on the package and purchase the appropriate amount for your job. If you want to augment your mix with lime, make sure to buy hydrated lime (also a dry powder). The ratio of sand to cement is about 3:1 by volume.
- Mix the dry ingredients. Using a shovel, smaller bucket or scoop, put three parts sand and one part cement into a mixing tub or trough, wheelbarrow, cement mixer or a 5-gallon (19 L) bucket. Add any dry additives according to the directions on the package and stir the powdered mixture thoroughly.
- Make sure not to make more than you can use in about two hours, as the mortar will set quickly.
- Adding lime to the mortar will improve its workability, make the mortar more water resistant, and will reduce the amount of shrinkage upon curing. Lime also helps prevent the cement and sand from separating.
- If you want to add lime to your mortar, replace about ten percent of the Portland cement with hydrated lime.
- Add water to the dry ingredients. Once you have mixed the dry ingredients thoroughly, add water a little bit at a time. Add a small amount of water, then distribute the water by carefully mixing with a spade or other tool. Keep adding water until the mortar reaches the proper consistency. It should be smooth and spreadable, but should not drip or run off your spade when you lift it. If you add too much water, you can adjust by adding more cement and sand.
- Once you have mixed the mortar, add any liquid additives and distribute them evenly through additional stirring.
- Clean your mixing tools at this time so that the mortar does not cure on the tool.
- Run clear water over the tool and rub with your gloved hand until all the mortar is removed.
- Use the cement mortar. Apply the mortar within about two hours of mixing it. If you wait longer than that, it will likely have cured too much to use, but the curing time can be extended by adding retarders and by keeping the mortar cool or cold. Once the mortar begins to set and harden, do not attempt to thin the mix by adding more water.
- Clean the tools. Run clear water over the tool and rub with your gloved hand until all the mortar is removed. If the mortar has set on the tools, beat the the tools to break off the dried mortar, then rinse while scrubbing.
Tips
- Partial list of additives:
- air entrainers to reduce the formation of air bubbles during the early curing stages (These help improve resistance to water penetration while marginally increasing strength and bonding.)
- hydrated lime (see above)
- plasticizers to take the place of lime-- These have a range of functionality.
- color additives to match existing mortar or to add decorative flair
- accelerators to speed curing (for use at low temperatures)
- reinforcing fibers to add strength and reduce early shrinking and cracking
- retarders to prolong the working time
- waterproofers to repel water and inhibit water penetration
- bonding agents to enhance bonding strength
- It is best to work with mortar on a cool, cloudy day. This will allow the mortar to cure more slowly. If this is not possible, it helps to keep the mortar out of direct sun, perhaps under a scaffold walk board.
Warnings
- Wear a dust mask when handling Portland cement or hydrated lime. Both are respiratory irritants.
- Wear heavy gloves and safety glasses when working with Portland cement or lime, as both can dehydrate and/or irritate the skin and eyes.
Things You'll Need
- Portland cement
- Masonry sand
- Hydrated lime (optional)
- Water
- Additives-- wet or dry (optional)
- Measuring bucket, scoop or shovel
- Mixing container: tub, trough, cement mixer, wheelbarrow or bucket
- Spade
- Heavy gloves
- Safety glasses
