PFA

This paper describes the effectiveness of a new pulverised fuel ash (PFA) activator when used in the form of fly ash bound mixture (FABM). Prior research in this area indicated that using extra limestone quarry waste dust in Type 1 road base material considerably reduces the ...

This paper describes the effectiveness of a new pulverised fuel ash (PFA) activator when used in the form of fly ash bound mixture (FABM). Previous researches in this field indicated that using extra limestone quarry waste dust in Type 1 road base material considerably reduces the stiffness of the unbound mixture. To regain the loses in resilient modulus, application of ground blast-furnace slag (GBS) and blend of PFA and hydrated lime was studied on road base materials containing high level of limestone quarry waste dust. 7 and 28 day resilient modulus measurement showed that GBS was not helpful while PFA-lime binder found to be useful in increasing the resilient modulus of the tested samples. However, to reduce the cost of utilisation, a new, cheaper activator for PFA was suggested to replace the hydrated lime.

From amongst six potential PFA activators, air pollution control (APC) residues presented the highest ability in providing bound road base material due to its higher pH and lime content. 7 and 28 day resilient moduli of the samples of FABMs containing i) extra quarry waste dust, and ii) APC residues and lime as PFA activators were investigated, and compared to the resilient behaviour of typical road base and subbase aggregates. Although both activators increased the resilient modulus of dust-elevated unbound mixtures, APC residues was found to provide much higher resilient modulus and less activation time in comparison with lime, while APC residues is a type of waste.