Chapter 7
Mixing Ratios and Job Preparation
Source section: cement and concrete mixing recipes, 2006 documentation set
The figures below are the mixing recipes recorded in the manual, for both pre-mixed bags and manually combined ingredients.
Mixing premixed concrete bags
| Quantity | Recorded figure | Applies to |
|---|---|---|
| Yield per bag | Approx. 2/3 of a cubic foot | One 80 lb bag of premixed concrete |
| Bags per square foot | Approx. 1/2 bag | A space 1 ft by 1 ft by 4 inches deep, in 2x4 forms |
| Water per bag | Approx. 1 gallon | One 80 lb bag of premixed concrete |
Mixing ingredients manually
| Ingredient | Share by volume | Note |
|---|---|---|
| Cement | roughly 10% | Type 1 Portland cement can be used for most residential jobs |
| Water | roughly 20% | Add in small amounts while mixing |
| Sand | roughly 30% | Available at most hardware stores and home improvement centers |
| Gravel | roughly 40% | Available at most hardware stores and home improvement centers |
Job preparation
- Use a CreteSheet for the mixing itself; see Chapter 2 for the seven-step sequence.
- Prepare forms or molds before mixing, or prepare the hole if placing a post for fencing or a deck footing. A typical form consists of wood 2x4s and 2x6s connected together to make a closed box or the desired shape.
- If an area is larger than 2 square feet, place wire mesh or something similar for reinforcement so as to prevent cracking. This could be remesh heavy gauge field wire or rebar. Ask your local hardware or building supply store for assistance if this is unfamiliar.
- While mixing, add water in small amounts.
- After mixing is complete, pour immediately. Do not allow the concrete or cement to harden before pouring.
- Leave concrete in forms or molds for at least 24 hours. Some quick-setting brands may require less time.
- Color can be added while mixing is underway with pigments, or the cured surface can be stained afterwards.
Caution on waterToo much water can weaken the concrete or cement once it has cured.
Note on colorPortland cement is gray or white and final colors will vary greatly when pigments are added.