Inspired by your situation, I decided to repair the cover of my huge spiral bound notebook which had torn along the perforations splitting it into two pieces. It sounds like the same thing that happened to you. It worked out great and didn't take very long.
You'll need pliers, strong pressure-sensitive tape, a small hole punch to fit the notebook holes. I got a rotary paper punch at a stationery store for a few dollars. The 1/16 inch (1.5mm) size was perfect for my notebook. You could even use a needle to make the holes in the tape.
Here's how I repaired mine step-by-step:
- Use a paper clamp on either end of the binding next to the spiral so the paper block pages remain aligned and won't come free.
- Unbend the end of the spiral so that you can twist it free, out of the row of spiral binding holes.
- Place the broken parts of the cover together so that the torn halves' holes align with each other.
- Tape both sides (front and back) of the cover with strong tape. I used thick crystal-clear packing tape and wrapped it around the edge—half along the front and half along the back. Masking tape or any paper-based tape won't last very long in use. Make sure that the kind of tape you use bonds with the cardboard card cover.
- Use a hole punch to open the holes covered with the tape.
- Align the cover with the paper block and clamp the assembly so it remains firm
- Twist the spiral back into the paper block holes to hold the notebook together.
- Re-bend the end of the spiral wire so that it remains secure.
While doing this project, you might decide to add divider, move some pages around, or even add some different kind of paper such as graph paper for other projects.