What is better, a RMC (ready-mixed concrete) or a mixer? RMC is produced by carefully weighing the cement, large aggregate, and fine aggregate, and adding admixtures like air-entraining chemicals, retarders, water reducers, and others. Most self-mixed concrete is done by adding ingredients by volumetric measurements (shovel fulls, bags full, or buckets full) and don’t utilize modern admixtures to compliment the product. Except where very small batches are needed, or difficulty in obtaining RMC is an issue, ready-mixed concrete will usually deliver a more consistent, predictable product.
If you decide to mix your own concrete, be careful to add only enough water to make the mix workable, and mix it thoroughly so that the ingredients are fully blended and the water is completely mixed into the concrete.