In this work, the flow behavior of a CO2 sorbent precursor (natural limestone) and a modified sorbent precursor, obtained by dry mixing the natural limestone and a silica nanostructured powder, is investigated. After dry mixing, small silica nanoparticle aggregates are seen to coat the limestone particle surface, which serves to decrease interparticle adhesion thus improving powder flowability. The tensile strength of the modified material subjected to small consolidation stresses has been tested before and after calcination. In addition, laser diffraction particle size analysis has been performed to test the mechanical strength of the aggregates as they are pre-dispersed in-situ by high energy processes such as high velocity air jets or ultrasonication in a liquid. The results also indicate that calcination leads to an increase of the average size of the limestone/nanosilica composite aggregates whose mechanical strength is enhanced as compared to that of calcined limestone aggregates. (C) 2013 Elsevier B.V. All rights reserved.