In　this　study,　the　micromechanical　properties　of　aggregates,　including　the　surface　energy,　nanohardness,　and　elastic　modulus,　were　investigated　using　an　atomic　force　microscope　(AFM).　The　Surface　energy　was　quantitatively　evaluated　by　applying　a　surface　energy　model,　whereas　the　surface　nanohardness　and　elastic　modulus　were　quantitatively　evaluated　using　the　contact-mechanics　model.　Further,　the　effects　of　the　aggregate　chemical　composition　and　limewater　treatment　on　the　surface　micromechanics　were　explored.　Four　natural　aggregates,　one　recycled　concrete　aggregate　(RCA),　and　one　recycled　brick　aggregate　(RCB)　were　used　for　the　experiments,　for　every　aggregate,　we　investigated　two　states,　the　original　state　and　that　after　the　limewater　treatment.　Results　showed　that　the　alkaline　components　(Al2O3　and　CaO)　on　the　surface　of　the　aggregate　have　a　positive　effect　on　surface　energy,　whereas　the　acidic　component　(SiO2)　has　a　negative　effect.　The　difference　in　aggregate　composition　results　in　the　surface　energy　of　the　original　basalt,　limestone,　and　diabase　being　three　to　four　times　those　of　the　original　granite,　RCA,　and　RCB,　respectively.　Therefore,　after　limewater　treatment,　the　surface　energies　of　basalt,　diabase,　granite,　and　RCA　increased　by　18.20%,　12.73%,　71.61%,　and　95.45%,　respectively,　whereas　those　of　limestone　and　RCB　decreased　by　10.06%　and　8.56%,　respectively.　The　increase　in　SiO2,　Al2O3,　and　CaO　contents　have　a　positive　effect　on　nanohardness　and　a　negative　effect　on　elastic　modulus.　After　limewater　treatment,　the　nanohardness　of　limestone　was　found　to　have　increased,　whereas　those　of　the　remaining　five　aggregates　(basalt,　diabase,　granite,　RCA,　and　RCB)　had　decreased.　The　CaCO3　attached　to　the　aggregate　surface,　causing　the　nanohardness　(1.5–7.0　GPa)　and　elastic　modulus　(21–32　GPa)　of　the　six　aggregates　to　approach　each　other.　©　2021