Durability of residential concrete using fly ash with a high alkali-sulfate content

Abstract

This project represents research performed to determine if Popcorn Calcite Deposition (PCD) occurs in residential concrete (i.e. concrete with relatively high water-to- cement ratio) produced with Ordinary Portland Cement (OPC) and fly ash with varying sulfate and alkali contents and if found, what is its affect on both mechanical strength and mass transport properties? Paste, mortar and concrete samples were cast with varying water to cementitious material ratio (W/CM) between 0.5 and 0.9 and were tested to determine the effect of carbonation on a wide range of properties. Carbonation in fly ash samples was shown to decrease the connectivity of calcium bearing phase, with it worsening as the W/CM increased. It was also observed carbonated fly ash samples underwent pore coarsening with this being more evident in samples made with high sulfate high alkali fly ash.