Aggregate　occupies　at　least　three-quarters　of　the　volume　of　concrete,　so　its　impact　on　concrete＇s　properties　is　large.　The　sieve　curve　traditionally　defines　the　aggregate　size　range.　Another　essential　property　is　grain　shape.　Both,　size　and　shape　influence　workability　and　the　mechanical　and　durability　properties　of　concrete.　On　the　other　hand,　the　shape　of　cement　particles　plays　also　an　important　role　in　the　hydration　process　due　to　surface　dissolution　in　the　hardening　process.　Additionally,　grain　dispersion,　shape　and　size　govern　the　pore　percolation　process　that　is　of　crucial　importance　for　concrete　durability.　Discrete　element　modeling　(DEM)　is　commonly　employed　for　simulation　of　concrete　structure.　To　be　able　doing　so,　the　assessed　grain　shape　should　be　implemented.　The　approaches　for　aggregate　and　cement　structure　simulation　by　a　concurrent　algorithm-based　DEM　system　are　discussed　in　this　paper.　Both　aggregate　and　cement　were　experimentally　analyzed　by　X-ray　tomography　method　recently.　The　results　provide　a　real　experimental　database,　e.g.　surface　area　versus　volume　distribution,　for　simulation　of　particles　in　concrete　technology.　Optimum　solutions　are　obtained　by　different　simplified　shapes　proposed　for　aggregate　and　cement,　respectively.　In　this　way,　reliable　concepts　for　aggregate　structure　and　fresh　cement　paste　can　be　simulated　by　a　DEM　system.　©　2012　Woodhead　Publishing　Limited　All　rights　reserved.