Variations in the microstructure of granular explosives (i.e., particle packing d., size, shape, and composition) can affect their shock sensitivity by altering thermomech. fields at the particle-scale during pore collapse within shocks. If the deformation rate is fast, hot-spots can form, ignite, and interact, resulting in burn at the macro-scale. In this study, a two-dimensional finite and discrete element technique is used to simulate and examine shock-induced dissipation and hot-spot formation within low d. explosives (68-84% theor. maximum d. (TMD)) consisting of large ensembles of HMX (C4H8N8O8) and aluminum (Al) particles (size ∼ 60-360 μm). Emphasis is placed on identifying how the inclusion of Al affects effective shock dissipation and hot-spot fields relative to equivalent ensembles of neat/pure HMX for shocks that are sufficiently strong to eliminate porosity. Spatially distributed hot-spot fields are characterized by their number d. and area fraction enabling their dynamics to be described in terms of nucleation, growth, and agglomeration-dominated phases with increasing shock strength. For fixed shock particle speed, predictions indicate that decreasing packing d. enhances shock dissipation and hot-spot formation, and that the inclusion of Al increases dissipation relative to neat HMX by pressure enhanced compaction resulting in fewer but larger HMX hot-spots. Ensembles having bimodal particle sizes are shown to significantly affect hot-spot dynamics by altering the spatial distribution of hot-spots behind shocks. (c) 2016 American Institute of Physics.