Chloride-induced　rebar　corrosion　is　a　common　degradation　process　for　concrete　infrastructures,　which　is　a　practical　concern　in　coastal　areas,　It　is　essential　to　study　the　chloride　diffusivity　behavior　in　concrete.　Considering　the　concrete　heterogeneity,　a　meso-scopic　numerical　model　based　on　the　finite-element　method　is　developed　for　the　simulation　of　chloride　diffusivity.　Concrete　is　regarded　as　a　heterogeneous　material　consisting　of　three　components,　i.e.,　aggregate,　mortar　matrix　and　the　Interfacial　Transition　Zones　(ITZs).　A　random　aggregate　structure　of　concrete　is　built,　in　which　the　mortar　matrix　is　considered　homogeneous.　The　aggregate　phase　is　set　as　impermeable,　and　the　chloride　diffusion　is　assumed　to　take　place　only　in　the　mortar　matrix　and　the　ITZs.　The　diffusion　properties　of　the　mortar　matrix　are　determined　based　on　the　water/cement　ratio,　degree　of　hydration　and　porosity　gradients　away　from　aggregate　particles.　The　transport　equations　are　solved　using　the　finite-element　method,　in　which　the　three　components　are　meshed　separately　and　the　continuity　in　fluxes　at　interfaces　between　them　is　applied.　The　present　numerical　model　is　validated　against　the　available　test　data　from　the　literature　and　compared　with　analytical　results　for　ideal　cases.　Using　the　finite-element　simulation　method,　a　parametric　study　has　been　undertaken　to　understand　the　influences　of　the　meso-structural　parameters,　including　aggregate　distribution,　aggregate　shape,　diffusivity　properties　of　the　ITZ,　water/cement　ratio　and　aggregate　content.　The　simulation　results　indicate　that　both　aggregate　distribution　and　aggregate　shape　have　a　negligible　influence　on　chloride　ingress　in　concrete,　the　diffusion　properties　of　the　ITZ　and　aggregate　content　have　a　significant　impact,　and　the　water/cement　ratio　has　a　marked　effect.　(C)　2014　Elsevier　B.V.　All　rights　reserved,