Concrete　cover　is　often　cracked　due　to　e.g.　shrinkage,　thermal　and　mechanical　loadings,　making　the　service　life　of　concrete　structures　severely　reduced.　The　diffusivity　are　strongly　dependent　on　the　micro-/meso-structure　of　concrete.　Considering　the　concrete　heterogeneities,　cracked　concrete　at　meso-scale　is　treated　as　a　four-phase　composite　composed　of　aggregate　particles,　cement　paste　matrix,　the　interfacial　transition　zone　(ITZ)　and　crack　phase.　A　meso-scale　simulation　model　for　the　investigation　on　the　chloride　diffusivity　into　heterogeneous　cracked　concrete　is　proposed.　In　the　model,　each　phase　has　its　own　mechanical　and　diffusion　properties.　The　aggregate　is　set　as　impermeable,　and　the　diffusion　properties　of　the　cement　paste　and　the　ITZs　are　determined　by　water-to-cement　ratio.　For　the　crack　phase,　the　diffusion　coefficient　is　obtained　by　fitting　the　available　test　data.　The　accuracy　of　the　developed　meso-scale　simulation　method　is　verified　and　discussed.　The　effect　of　artificial　crack　and　tortuous　crack　on　the　chloride　diffusivity　is　explored.　The　simulation　results　indicate　that　the　developed　meso-scale　model　can　successfully　describe　the　chloride　diffusivity　into　cracked　concrete.　Moreover,　it　is　found　that　the　apparent　chloride　diffusivity　in　cracked　concrete　depends　on　not　only　the　crack　width　but　also　the　crack　depth.　(C)　2015　Elsevier　Ltd.　All　rights　reserved.