The important aspect in this question in addition to influence of inner structure is a type of loading.
The behaviour of compressive strength concrete, mortar and cement paste under static and dynamic loadings is different. In the case of quasi-static experiments, the fracture stress of mortar and concrete is almost coincide. However, dynamic loadings on split Hopkinson pressure bar shows a return dependence.
I can understand that the concrete will be highest due to the presence of coarse aggregates, but is there any evidence of chemical bonds between the aggregates and the mortar/cement paste? If so is it also responsible for strength development? Also is there any chemical bonds between cement paste and sand particles?
Mortar to concrete relationship mostly affects by a factor of ITZ..if thickness of this weak itz zone is high..there is a possibility of mortar getting high strength than concrete.