Using no-mix concrete, often called post-hole concrete, is a straightforward process ideal for setting posts quickly by adding water directly into the hole with the dry mix.
No-mix concrete is designed for simplicity, eliminating the need to pre-mix the concrete in a wheelbarrow or mixer. Its primary use is for setting fence posts, mailboxes, and similar structures directly in the ground. The concrete mix contains a fast-setting binder that cures rapidly once it comes into contact with water.
The Basic Steps
The process involves digging the hole, placing the post, adding water, and then pouring the dry concrete mix. The mix then hardens around the post as it absorbs the water.
Based on common practice and available references, the key steps for using no-mix concrete to set a post are:
- Prepare the Hole: Dig a hole to the required depth and width for your post. Ensure the bottom is firm.
- Position the Post: Place your post into the center of the prepared hole. Use a level to check that it is approximately centered and plumb (vertical). You may need to temporarily brace the post to hold it in position.
- Add Water: Have your partner fill the hole approximately 1/3 full of water. This is a crucial step where the water goes in before the dry mix.
- Add the Dry Mix: Wearing respiratory protection, carefully pour the dry mix into the hole, working evenly around the post until it is filled to the desired level (typically just below ground level). The dry mix will begin to absorb the water and settle.
- Allow to Set: The concrete will begin to harden very quickly. Check the plumb of the post again and make any minor adjustments immediately after adding the mix.
Process Overview Table
Here's a simple breakdown of the core process:
| Step | Action | Notes |
|---|---|---|
| Preparation | Dig hole, position and brace post. | Ensure hole is deep enough and post is plumb. |
| Hydration | Add water to the hole (approx. 1/3 full). | Water goes first for no-mix varieties. |
| Mixing | Pour dry concrete mix around the post. | Wear mask; distribute evenly. |
| Curing | Allow concrete to set; check post plumb. | Fast-setting time; limit disturbance. |
Practical Tips for Success
- Hole Size: Ensure the hole is wide enough to allow the mix to flow around the post, but not excessively large, which wastes material. A common guideline is three times the post diameter.
- Water Amount: The "1/3 full" is a guideline. You want enough water for the mix to fully hydrate without creating a soupy mess. You can add a little more water on top after pouring the dry mix if it looks too dry, but avoid overwatering.
- Respiratory Protection: As noted in step 3 of the reference, wearing respiratory protection is important when handling dry concrete mix to avoid inhaling dust.
- Working Quickly: No-mix concrete sets very fast. Have your partner ready with the water and work efficiently once you start adding the mix.
- Tamping (Optional): Some people gently tamp the dry mix with a stick to help settle it and ensure it contacts the water and post evenly.
- Bracing: Keep the post braced and still while the concrete sets, which can be as little as 15-20 minutes depending on the specific product and conditions. Avoid putting load on the post until fully cured (check product instructions for full cure time).
By following these steps, you can effectively use no-mix concrete for setting posts, achieving a strong and stable base without traditional mixing methods.
