The Rule of 6’s: The Secret to Perfect Concrete

concrete mix ratio, how to make concrete

The rule of 6’s creates the perfect mixture for concrete success. Utilizing this formula has proven to work for all different concrete types, as well as a wide range of construction and renovation projects.

Mixing concrete is as much an art as it is a science. Knowing the basics of how to make concrete is one thing, but understanding the secret to perfect concrete is another matter altogether. Once you have learned how to create the perfect concrete mix ratio—thanks to the rule of 6’s—you can implement that knowledge with all your construction and renovation projects.

How to Make Concrete With the Rule of 6’s

The rule of 6’s condenses into four basic principles using varying measurements of six. Keep these principles in mind when you’re creating concrete:

  • Minimum cement content of 6 bags per cubic yard of concrete
  • Maximum water content of 6 gallons per cement bag
  • A minimum 6 day curing period
  • 6% air content

Adhere to the first principle by using a minimum cement content of 6 bags per cubic yard of concrete (4,000 PSI). Cement is what holds your concrete together, so don’t stint on the cement! Next, limit your water content to a maximum of 6 gallons per cement bag. Too much moisture can make your concrete weak and porous.

The curing period (the period of time that concrete should stay moist) should last a minimum of 6 days, and concrete that is subjected to freezing and thawing ought to have an air content of 6 percent. If you shorten your curing time it can weaken your concrete or keep it from setting evenly. Without the correct air content, concrete is more likely to crack in extrememe temperatures because it doesn’t have enough flexibility.

Making Adjustments to the Rule of 6’s

Before pouring concrete and using the rule of 6’s, it helps to consider your upcoming consruction or renovation project. The perfect concrete mix ratio will change slightly depending on the requirements of your project.

For example, interior concrete work which does not need to withstand freezing and thawing cycles requires a 3,000 PSI mix without the need for air entrainment. As such, you can skip the “air content of 6 percent” aspect of the rule of 6’s.

The air content rule is reserved for freezing and thawing cycles, but the rule of 6’s should be taken only as a general rule. Sometimes, extra precautions are needed. For example, in areas with harsh winter weather, a 7 bag mix, 4,000 PSI concrete and as much as 8% air content help avoid spalling of the concrete surface.

In effect, the rule of 6’s is a great guide for most concrete work, but like almost any rule, exceptions should be made when necessary. Another consideration not mentioned in the rule of 6’s is that fiber mesh and/or a retarder may be required to lessen the risk of shrinkage cracks while enhancing the concrete’s workability.

Fiber mesh increases toughness and strengthens post-crack load carrying capacity while retarders counter the drying effects of hot weather by delaying the concrete’s setting. Depending on the climate and weather, one or both of these strategies may need to be included in your perfect concrete mix ratio.

If you need a commercial concrete supplier in Arkansas, contact Razorback Concrete at 870-455-0700 to speak with an experienced project manager. We can help you determine the perfect concrete mix ratio for your construction project!

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