Bottom ash can be used as pelletizing seeds in unsintered artificial lightweight aggregates, so it can be called as ‘cold-bondedaggregates’. In the present study, the mechanical and chemical characteristics of bottom ash aggregates cold-bonded with fly ash wereinvestigated. The crushing strength and the water transfer characteristic of the aggregates, which may affect the strength gain of theconcrete, were evaluated. Moreover, the degree of hydration and the hydration products of the aggregates were analyzed to verify thechemical stability of the aggregates. Compared to commercialized artificial lightweight aggregates manufactured by sintering process,cold-bonded fly/bottom ash aggregates had similar levels of water transfer characteristics, while having lower strengths. The calciumhydroxide in the aggregates was almost completely consumed after 28 days moist curing.