Influence of the metakaolin on porous structure of matrixes based in mk/cement

Abstract

The incorporation of pozzolanic materials in the manufacturing of blended cement has a positive effect on the improvement of blended mortar and concretes performances. These active additions modify porous structure, impeding or delaying the access of aggressive solutions and, therefore materials more durable are possible of obtaining. An increase or decrease on the durability of blended pastes, mortars and concretes will depend on chemical and mineralogical compositions, fineness and reaction kinetics of these pozzolans. The current work shows the results of a research carried out in blended pastes to know the effect of activated material (metakaolin) on the microporosity of pastes elaborated with different amounts of mk (0-25%). A water/ binder ratio of 0,55 was used. Samples were cured at 20ºC for 360 days. The evolution of total, capilary and gel porosity as well as average pore size were carried out through mercury intrusion porosimeter (MIP). Also, the helium pycnometer as alternative method to obtain additional information about porosity above 1,4 Å was used. A good correlation between both methods has been obtained. In addition, it is proposed the best mk content for the elaboration of mk-blended pastes.