Cement, when combined with sand and water, becomes mortar, a crucial component in masonry construction. Here's how to use cement to create mortar for laying bricks, blocks, or stones:
Mixing Mortar: A Step-by-Step Guide
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Gather Your Materials: You'll need Portland cement, sand (masonry sand or sharp sand is best), water, a mixing container (mortar tub or wheelbarrow), and a shovel or hoe. A gauging trowel can also be helpful for measuring.
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Determine the Mix Ratio: The correct mix ratio of cement to sand is crucial for a strong and durable mortar. A common ratio is 1 part cement to 3 parts sand (1:3). Different ratios can be used depending on the specific application and desired strength. Consulting local building codes or a structural engineer is advisable for critical applications. A typical Type N mortar is 1:1:6 (Portland cement: lime: sand). For pointing, a 1:3 cement-sand mortar is common.
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Dry Mix: In your mixing container, thoroughly mix the cement and sand in the appropriate ratio while they are dry. This ensures even distribution of the cement throughout the sand.
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Add Water Gradually: Slowly add water to the dry mix, mixing continuously. The goal is to achieve a workable consistency, similar to thick peanut butter or pudding. Avoid adding too much water at once, as this can weaken the mortar.
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Mix Thoroughly: Continue mixing for several minutes to ensure all ingredients are properly combined and the mortar is smooth and consistent. There should be no dry pockets of cement or sand. A mortar mixer will improve the mixing process.
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Check the Consistency: The mortar should be plastic and easily spreadable. It should adhere well to the trowel and the bricks or blocks. If it's too dry, add a little more water. If it's too wet, add more cement and sand in the correct ratio.
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Let it Slake: Allowing the wet mortar to sit undisturbed ("slake") for 10-15 minutes after initial mixing improves its workability. Remix briefly before using.
Applying the Mortar
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Prepare the Surface: Ensure the surfaces of the bricks, blocks, or stones are clean and free of debris. Lightly dampen the surfaces to improve mortar adhesion.
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Apply the Mortar Bed: Using a trowel, apply a layer of mortar to the surface where you'll be placing the brick or block. The thickness of the mortar bed should typically be around 3/8 inch (10 mm).
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Position the Brick/Block: Carefully place the brick or block onto the mortar bed and gently press it down, ensuring it is level and aligned with the surrounding units.
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Create Head Joints: Apply mortar to the end of the brick or block before placing it against the adjacent unit, creating the head joint.
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Remove Excess Mortar: Use your trowel to remove any excess mortar that squeezes out from the joints.
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Tooling the Joints: Once the mortar has partially set (but is still pliable), use a jointing tool to create a consistent and aesthetically pleasing finish to the joints. Common joint finishes include concave, V-joint, and flush. Tooling compacts the mortar, making a watertight seal.
Important Considerations
- Portland Cement vs. Masonry Cement: While Portland cement is the core ingredient, masonry cement is a pre-blended mix of Portland cement and other ingredients (like lime) designed specifically for mortar. Masonry cement can improve workability and water retention.
- Lime: Adding lime to the mortar mix improves its workability, water retention, and flexibility. A common mix using lime is 1 part Portland cement, 1 part hydrated lime, and 6 parts sand (1:1:6).
- Weather Conditions: Avoid mixing or applying mortar in freezing temperatures or direct sunlight. Protect freshly laid masonry from rain and extreme temperatures.
- Safety: Wear appropriate personal protective equipment (PPE), including gloves, eye protection, and a dust mask, when handling cement and mixing mortar. Cement dust is caustic and breathing it can cause respiratory issues.
- Curing: Mortar requires moisture to properly cure. Lightly misting the mortar joints with water for several days after application can help improve its strength and durability. This is especially crucial in hot and dry weather.
- Color: Cement comes in grey and white. White cement can be used for esthetics.
