Physico-chemical properties, porosity and microstructure of sustainable concretes

Abstract

This paper deals with the properties and microstructure of sustainable concretes (SC) made with recycled concrete coarse aggregates and include different proportions of supplementary cementing materials (SCM) such as silica fume (SF) and flyy ash (FA). From test specimens different parameters were determined that define the minimum properties demanded by regulations to guarantee the durability and stability (mechanical and microstructural) of concrete. From the results it can be deduced that with 100% of recycled concrete aggregates (RCA) and SCM, greater compressive strength was obtained than specified in regulations and as determined in reference specimens. From SEM image analysis a low, porosity in the interfacial transition zone (ITZ) and a dense cementitious matrix were found. Consequently, it is recommended to control the use of these materials (RCA) by limiting the values of porosity or to require the addition of SCM able to diminish the porous network and to guarantee a greater structural density of the material.