Maximum Density Method:

This method is economical to design for a minimum amount of cement-water paste in a concrete mix. Fuller suppose that the greater the amount of solid particles that can be packed in a given volume of concrete, the higher will be its strength. In this method, the aggregates should be graded in such a way that the mixture attains the maximum density. Fuller suggested curves for this reasons that are based on,

P = 100 (d/D)^0.5

where, D = Maximum size of coarse aggregate,

P = Percentage of total material smaller than size d, and

D = Maximum size of fine aggregate.

The drawback of this method is that the effect of particle interference is ignored. The aggregates graded to give maximum density results in harsh and practically unworkable mix. The workability could be improved only when there is excess of paste above that required to fill the voids in the coarse aggregate.

Suppose it is desired to grade a mix with 20 mm maximum size coarse aggregate and 4.75 mm fine aggregate, then the value of P, i.e. percentage of material finer than 4.75 mm, will be given by 0.5

P = 100 ( 4.75/20)

= 8.73

= say 50%.