Mechanical Behavior of a New Base Material Containing High Volumes of Limestone Waste Dust, PFA, and APC Residues

The results of research are reported in this work that evaluated the benefits of the stabilization of Type 1 subbase material to which had been added a high volume of limestone quarry waste dust. There is extensive interest in introducing large volumes of quarry waste dusts to the Type 1 subbase that is used in the construction of the vast majority of foundations for roads and other pavements in the United Kingdom. Previous experience has indicated that replacement of 10–30% of Type 1 subbase with limestone quarry waste dust made the mixture inadequate for pavement foundation purposes. When pulverized fuel ash (PFA) and lime were added to these materials, the new mixture improved to a level that made the materials suitable for use as subbase in pavements. However, lime was still a costly industrial product and a major CO2 emitter. The replacement of lime with another capable PFA activator of waste or recycled origin was sought. After examining several potential wastes, it was found that air pollution control (APC) residues could not only activate the PFA to stabilize the Type 1 subbase containing high volumes of limestone quarry waste dust, but created a final mixture of more desirable mechanical properties than generated by PFA–lime. Unconfined compressive strength, resilient modulus, and plastic deformation of both PFA–lime and PFA–APC residue stabilized materials have been studied to reveal the performance of the novel binder of PFA and APC residues in enhancing the mechanical properties of Type 1 subbase to which was introduced high volumes of limestone quarry waste dust. The final mixture has significantly contributed to accommodating three types of waste materials to be used in pavement foundations.