Step 1

Remove the Damaged Step
Use a concrete saw with a hose attachment to remove damaged part of step. The hose helps keep the blade cool and keep down dust. ( Follow the manufacturer's instructions for safe use of the concrete saw.)
Step 2

Build a Form
Build a form for the step. In our case, we used a piece of lumber. Spray form with cooking oil to keep it from sticking to concrete.
Step 3
Fill the Form With Concrete
Mix concrete to manufacturer's instructions and pour into form. Tap form to remove air pockets in the cement and to help it settle. Use a magnesium float to smooth the cement. Finish off with a trowel. Remove form. Avoid walking on the step for 24 hours or more, depending on the cure rate for your cement product.