Impact of gap-graded cement blending on strength, permeability and CO₂ footprint of concrete

P. Stroeven

Faculty of Civil Engineering and Geosciences, Delft University of Technology, the Netherlands

Partial replacement of Portland cement by pozzolanic mineral admixtures exerts direct positive effects on the CO₂ footprint of concretes. The low CO₂ footprint is reinforced by making use of incinerated specific organic waste, such as rice husks, resulting in rice husk ash (RHA). In this way, the CO₂ footprint of obtained concrete is improved. A gap-graded binder leads to improved particle packing density with RHA as the finer component (the filler function), so that high strength concretes can be produced. This is reinforced by the pozzolanic nature of the RHA. 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. Therefore, this paper applies a relatively new economic and reliable approach to conduct such investigations on computer simulated (virtual) particulate materials. Application demonstrates the favorable impact of gap-graded blending on pore characteristics relevant for transport related phenomena. The involved reduction in permeability of the uncracked material will therefore promote this aspect of durability, being an essential element of the environmental footprint.

Key words: Cement, blending, CO₂ footprint, computer simulation, gap-grading, porosimetry, strength, durability