Category Archives: Cement And Concrete

Concrete Repairs For The Home

Repairs to concrete are easy to conceal, provided that you take care to match the finish to the existing surface texture.

Cracks

The occasional crack in a concrete path can occur for various reasons and it is simple to fill in the damage. However, where there are numerous cracks and depressions the cause is likely to be poor foundations in which case there is little alternative but to break up the concrete and start again from scratch.

For an occasional crack use a mix of 1 part cement to 3 parts sand or buy a suitable bag of dry-mixed cement mortar. In either case it is well worthwhile adding a little PVA adhesive to the mix; this acts as a bonding agent to ensure a firm grip between the old and the new concrete. Check the manufacturer’s instructions for exact details for using the adhesive.

Use a cold chisel and club hammer to undercut the crack — this forms it into an inverted ‘V’ shape with the point of the ‘V’ at the surface. The filling material will then be well anchored. Clean all dust from the crack and then brush a coat of diluted PVA adhesive on to the crack to serve as a primer. Provided that the repair mix is on the dry side it will be easy to pack it down well into the crack and to level it off with the surface. Sometimes a steel float makes it easier to leave a level finish.

Holes

Holes in the surface are mostly found near cracks. They can be caused by weak foundations too (if there are several the concrete mix may have been too weak). Repair them as for cracks.

Crumbling edges

These are often caused by removing the formwork before the concrete was fully hardened. Another possibility is that the concrete mix was not pushed well down into the edges, leaving an air pocket below the surface.

Break up the crumbling edge with a cold chisel and club hammer, going back to firm material. Remove loose material and tamp down the foundations, adding new hard-core if needed. Set up a formwork alongside the repair and brush PVA adhesive on to the exposed edge. Mix up a batch of 1 part cement to 5 parts ballast (or use a bag of dry-mix) and add a little PVA adhesive. Press the mix well down into the edge of the formwork. Allow four weeks before removing the formwork.

Depressions

Hollows where puddles form can be filled successfully only if they are more than about 12mm deep. If less than this, the area will have to be broken up and relaid. Repair the hollow using the mix and techniques specified for cracks. Formwork is needed if the edge of the concrete is affected.

Concreting Skills Explained

Concrete is made by mixing together aggregates (sand, and gravel or stones) and cement with water. For most DIY jobs you can use all-in aggregates, or ballast. There are different types of cement available but for most DIY jobs ordinary Portland cement will do. This is light grey in colour and is normally supplied inContinue Reading

Exterior Concrete Repairs

Many outside repairs need concrete, mortar or cement. The important constituent is Portland cement, which is bought as a fine powder. It is cheapest when bought in large bags, but as it will deteriorate and harden if kept for long after opening, it may be more economical to buy only sufficient for a job. AContinue Reading

Mixing And Using Cement

One of the most common materials used in home and garden is cement. There are two main types of cement mixture mortar and concrete. In mortar, cement is mixed only with sand. It is used for building in bricks or concrete blocks and also for the final surfacing of floors and some outdoor walls. Concrete,Continue Reading

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