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So, is there a "best" grading for aggregates for concrete?
Grading of aggregates is important as it affects workability of fresh concrete. And workability is related to water and cement requirements in concrete mixes. Workability influences segregation and the placing and finishing of concrete.
In other words the properties of fresh concrete is affected by grading of aggregates for concrete. As a result the properties of hardened concrete would also be affected.
In coming up with the desired aggregate grading, the following factors are taken into consideration:
Surface area of aggregates
Relative volume occupied by aggregates
Workability of concrete mix
Tendency to segregate
Concrete experts have come up with various methods to arrive at an "ideal" grading that would be applicable to all aggregates. However none have been found to be universally acceptable mainly due to economic considerations. Also the factors like particle shape, particle texture and cement types come into play.
However it is possible to come up with grading specifications which on the average will produce a concrete of satisfactory properties from materials available in a particular area.
So, work towards a specification by collecting and analysing enough test data using materials at your location. That is the best and closest you will ever get to the "best" gradation of aggregates for your concrete mix.