This　paper　describes　the　development　of　a　micromechanical-based　constitutive　model　accounting　for　the　effect　of　internal　expansion　on　the　residual　elasticity　of　a　Hashin　composite　material.　This　material　is　made　of　spherical　inclusions　that　are　subjected　to　gradual　swelling　within　a　quasi-brittle　matrix.　The　main　focus　of　this　work　is　to　describe　and　analyze　the　material　mechanical　response,　with　an　additional　focus　on　the　internal　swelling＇s　effect　on　the　stress–strain　response　and　residual　elasticity.　Microstructural　features　and　parameters　of　major　importance　for　the　mechanical　responses　were　identified.　The　innovative　characteristics　of　the　proposed　approach　are　summarized　as　follows:　(1)　a　full　determination　of　the　physics　of　a　complete-damage　problem　throughout　the　whole　process　of　inclusion　swelling　with　upscaling　techniques,　which　transfers　the　microcrack-related　properties　from　the　lower　scale　to　upper　scale;　and　(2)　an　evolution　of　the　mechanical　fields　and　the　corresponding　residual　elasticity　for　various　inclusion　swelling　levels.　Concerning　the　matrix–inclusion　composite,　it　was　hypothesized　that　only　the　matrix　was　susceptible　to　cracking,　with　varied　degrees　of　damage,　whereas　the　inclusions　behave　elastically　and　the　elastic　modulus　of　the　expanding　inclusions　remains　constant.　It　is　to　emphasize　that　the　gradual　swelling　of　inclusions　is　modeled　by　an　increasing　strain　in　the　current　micromechanical-based　constitutive　model,　and　the　microcracks　are　represented　by　a　set　of　randomly　oriented　penny-shaped　microcracks　with　identical　radii　(namely,　closed　cracks).　The　main　contribution　of　the　current　research　is　to　establish　the　exact　mathematical　solutions　for　the　mechanical　fields　(stress,　strain)　caused　by　the　swelling　of　the　inclusions　(mechanical　loading)　and　derive　the　effective　residual　elasticity　of　a　composite　(structural　response)　subject　to　internal　expansion　and　quasi-brittle　damage.　Based　on　the　assumption　of　closed　cracks　that　could　be　extended　to　open　cracks　in　the　upcoming　work,　the　results　proposed　by　the　present　paper　help　to　understand　the　non-linear　mechanical　behavior　of　quasi-brittle　materials　subject　to　microcracking　and　provide　a　theoretical　framework　to　be　used　as　academical　benchmark　for　numerical　simulations.　©　2022