Concrete is often seen as a stable and permanent material, but it is actually porous and absorbs water. When the water trapped inside the concrete freezes, it separates the cement binder, causing crumbling. If you live in an area with winter temperatures low enough to freeze water, seal the steps or concrete walkway with a sealer once a year to prevent water from entering. Salt is slightly acidic and attacks the bonds that hold the concrete together, widening the pores of the concrete and allowing more water to seep inside.
When the temperature drops and the water freezes and expands, the concrete surface will chip or flake off. After years of salting and freezing, concrete begins to show real deterioration. To avoid this, use a penetrating concrete sealant. It is one of the most cost-effective ways to prevent crumbling and flaking.
If your steps, hallways, patios, etc. walls of concrete are crumbling, you may be able to repair them with traditional products and methods or you can choose from some modern materials. Use only the amount of water indicated in the instructions for the mixture to prevent weak concrete from crumbling under pressure. Buy epoxies that are clearly labeled as concrete patch materials and follow the directions on the label for amazing results.
Depending on the depth of damage, you will need to use a sand mixture (up to 2 thick) or a standard concrete mix (more than 2) to perform the repair. To repair deeper concrete defects or to replace missing pieces of concrete, simply add small stones to the mixture. For hard-to-remove stains on outdoor slabs, use a Quikrete concrete and asphalt cleaner which is applied with a stiff brush and then rinsed with a hose. If you add too much moisture during the mixing phase, the chemical bonds that create a strong and durable concrete surface will be weaker.
Once the patch mixture begins to harden, you can use a wooden trowel or a magnesium or steel float to match the texture of the surrounding concrete.