New insight on the restructuring and breakage of particles during uniaxial confined compression tests on aggregates of petroleum coke

With the aim of modelling the mechanical behaviour of carbon anode paste, compression tests within a rigid mould were performed on different recipes of carbon paste containing 32 to 44 wt.% binder. The compression was performed by applying a series of loading/unloading cycles. The maximum load was incrementally increased at each cycle. Test results showed that a softening behaviour occurs after the hardening of the anode paste during compaction cycles. This paper attempts to explain the mechanism of this peculiar behaviour. For comparison, two cokes with different shape factors were used to prepare the paste recipes. It was observed that round particles result in less resistance to local shear stress than do the angular ones. Binder, which consists of coal tar pitch and fine coke particles, acts as a lubricant enhancing the compaction of the paste. The breakage and slippage of particles during loading were monitored using an acoustic measurement system. A creep test, performed on a carbon paste and dry aggregates, corroborates that the time-dependency, or creep, of the paste is mainly governed by the solid skeleton.