High filler concrete using fly ash - Chloride penetration and microstructure
S.L.A. Valcke1, R.B. Polder1,2, T.G. Nijland1, G.A. Leegwater1, J.H.M. Visser1, A.J. Bigaj-van Vliet1
1 TNO Technical Sciences, Structural Reliability, PO Box 49, 2600 AA Delft, The Netherlands
2 Delft University of Technology, PO Box 5048, 2600 GA Delft, The Netherlands
Most high filler concrete studies are based on relatively high contents of powder (cement + filler) (>400 kg m-3). This paper aims to increase the total fly ash content relative to the clinker content, while simultaneously minimizing the total powder content in the concrete to values lower than 300 kg m-3. The motivation for decreasing the total powder content using fly ash as a cement replacement is based on the fact that concrete structures often have an ‘overstrength’ related to excess cement. Consequently, there is potential for using lower amounts of clinker and replacing it by filler, which can reduce the amount of primary raw materials used and CO2 related to clinker production. However, the question arises if sufficient durability of this ‘high filler’ concrete is achieved. In this paper chloride penetration resistance is measured by rapid chloride migration and diffusion tests on both laboratory mixes and samples from pilot projects. Also, electrical resistivity and polarization-and-fluorescence microscopy (PFM) are used to evaluate the development of the microstructure in time. The results show possibilities and limitations of high filler concrete in achieving long service life.