Effects of volumetric aggregate fraction on transport properties of concrete and mortar

Abstract EN

In this paper, different transport tests are carried out on concrete and mortars of different paste contents to examine their behavior with gradually increasing Aggregate Fractions (AF).

In general, it was found that transport of gas and electrical conduction decreases with increasing AF.

However, a Critical Aggregate Fraction (CAF) was discovered in OPC mortars at which the transport through mortar, or porosity, had a positive jump, beyond which the decreasing pattern resumed.

This CAF in tested mortars was at AF of 0.35.

Results and existing theories are discussed and it is argued that neither theories of ITZ percolation [10] nor the percolation of the porous patches in paste [7] can justify this newly discovered phenomenon or explain why this jump disappears after CAF rather than the effect being exacerbated.

Also, some questions are raised and a need for further tests is established to elucidate this phenomenon.

Furthermore, some ambiguities are raised and the need to understand what exactly happens to the paste in concrete and its porosity as the volume of the aggregate is increased to and beyond this CAF is highlighted.