"No mix concrete," often referring to a specific application method for standard preblended concrete mixes, works by placing the dry mix into the desired form and then hydrating it in place over time. This method avoids the traditional step of mixing concrete with water in a wheelbarrow or mixer before placement.
The Process Explained
Instead of pre-mixing, bags of preblended concrete mix (such as Quikrete or Sakrete), which already contain cement, aggregate, and sand, are directly used.
Here's a breakdown of the typical steps:
- Prepare the Subgrade: The area where the concrete is to be placed is prepared, often by compacting the soil. The subgrade is then typically dampened.
- Place the Dry Mix: Bags of the dry, preblended concrete mix are simply dumped directly into the prepared forms.
- Level the Mix: The dry mix is then leveled off within the forms using tools like a heavy steel rake or screed to achieve the desired height and surface profile.
- Hydrate in Place: Water is then applied to the dry concrete over a period of several hours. This is often done by misting with a hose, which allows the water to slowly permeate and moisten the dry concrete mix throughout the form.
This slow, in-situ hydration allows the cement to react with the water, binding the aggregate and sand together to form hardened concrete directly within the final shape.
Why Use the "No Mix" Method?
This application method is particularly popular for certain projects where:
- Simplicity is key.
- Traditional mixing equipment isn't readily available or needed for small jobs.
- Minimizing mess outside the form is a priority.
Common applications include fence post setting, mailbox posts, or small, simple footings where convenience outweighs the need for strict control over water-cement ratio and homogeneity typically achieved with pre-mixing.
Key Components
This method relies on the properties of standard preblended concrete mix:
| Component | Purpose |
|---|---|
| Cement | The binder that reacts with water. |
| Aggregate | Provides strength (gravel, crushed stone). |
| Sand | Fills voids and improves workability. |
| Water (added) | Activates the cement for hydration. |
By adding water after placement, the hydration process occurs directly in the form, essentially "mixing" the concrete in its final location.
