At present, aggregates cannot be transported over long distances; we may well know the characteristics of the ideal sand and coarse aggregates, but we cannot obtain such aggregates. In other words, we can only use existing materials. After research, we came up with the following basic principles:
1. As long as the concrete meets the workability requirements and the aggregate is clean and firm, the strength of the concrete mixture depends on the amount of water in the batch, which can be expressed by the volume ratio of water and cement.
2. The effect of different cement dosages can be reflected by the difference in water-cement ratio.
3. The design of the concrete mix ratio must be based on the screening analysis of the aggregate. Under the conditions of determining the workability of concrete, there is a very close relationship between the particle size and gradation of the aggregate and the required water consumption.
4. Aggregate is not necessarily, and it is not worthwhile to proportion according to any fixed gradation; the gradation of aggregate may vary in a wide range, but it does not necessarily affect the amount of water or the quality of concrete.
5. Plasticity or workability is the basic requirement of structural concrete.
