For larger imperfections in concrete, a mortar mix is the best solution. To make your own mix, combine one part Portland cement, three parts masonry sand, and just enough water to form a thick paste. You can also buy ready-made repair mortar mixes from local stores or online. Before applying the mortar, you must prepare the concrete surface for adhesion.
Make sure it is even, free of dirt and slightly damp. Applying a scrape coat to the concrete surface will help the mortar adhere better. For best results, use Thinset mortar. You will need patching mortar and liquid bonding agent to help the new patch adhere to old concrete. Mix the mortar with water as directed.
Alternatively, you can use an epoxy or latex patch compound for small jobs. These compounds form a stronger bond, do not require a bonding agent and are self-healing. However, they are expensive for big jobs. QUIKRETE Zip& Mix repair mortar is a multi-purpose concrete repair material that can be mixed and used directly from its innovative resealable bag. It is ideal for repairing broken edges and corners in concrete steps and curbs, slabs, concrete walls and masonry and can even be used for aerial applications without the need for formwork. If there is a small crack left around the repair, trowel the patch compound into the crack, and then smooth the patch level.
Allow the mortar to cure for at least three days and avoid putting weight on the corner for a few days afterwards. Despite their similarities in composition, mortar will only adhere to concrete if it is wet. If the concrete surface you are working with is dry, it will draw all of the moisture out of the mortar mix you are applying. In addition to keeping concrete moist while applying mortar, make sure to clean concrete surfaces thoroughly to ensure a successful project. Basically, concrete is stronger and more durable than mortar, so it can be used for structural projects such as mounting posts. Mortar mix is more designed to bond stone, brick and concrete block, so it may not be a good choice for a finished surface.
Although both concrete and mortar contain cement and sand, adding gravel and other aggregates makes concrete stronger than mortar. If you need help deciding which material is best for your project, Quikrete has a live chat option on their website that can provide useful advice.