The choice of a concrete mix depends on the need of the project both in terms of strength and appearance and in relation to local legislation and building codes.
But by and large, the ideas I'm about to explain hold true.
The 10-20-30-40 Rule Let's start by discussing the essential ingredients of concrete.
A typical concrete batch, by volume, contains roughly 10% cement, 20% water and air, 30% sand, and 40% gravel (see Figure 1).
The exact proportions vary up or down a little, but 10-20-30-40 is a good rule of thumb.
If you understand the fundamentals, you'll keep costs down, improve the strength of your concrete, and minimize cracks.
Ready-mix plants all around the country sell hundreds of different concrete mixes.
These requirements take into consideration the weather conditions that the concrete will be exposed to in service, and the required design strength.
The compressive strength of a concrete is determined by taking standard molded, standard-cured cylinder samples.
Fine-tuning your mix and your techniques can get pretty complicated.