Partial replacement of Portland cement by pozzolanic mineral admixtures exerts direct positive effects on CO2 emissions. The green character is reinforced by making use of incinerated vegetable waste, such as rice husk ash (RHA). Gap-grading leads to improved particle packing density with RHA as the fine component, so that high strength concrete can be produced. Characteristics of the capillary pores developed in the hydrating binder have impact on the transport-based durability properties. Yet, their assessment constitutes a complicated problem, especially in experimental approaches. This paper, therefore, presents a new economic and reliable approach to conduct such investigation by DEM. Application demonstrates the positive effects of gap-gi'aded blending.