Low-heat　Portland　cement　(LHPC)　is　an　environmentally　friendly,　low-carbon　cementitious　material.　However,　its　limited　early　mechanical　properties　significantly　restricts　its　applications.　This　work　aimed　to　improve　the　early　mechanical　properties　of　LHPC　through　the　synergistic　effect　of　diethanol-isopropanolamine　(DEIPA)　and　gypsum　(CaSO4·2　H2O).　The　research　investigated　the　effects　of　DEIPA　and　gypsum　on　the　early　mechanical　properties,　hydration　kinetics,　pore　solution,　hydration　products,　pore　structure,　and　microstructure　of　LHPC.　The　results　demonstrated　that　the　addition　of　0.03　%　DEIPA　alone　(3D　group)　increased　the　compressive　strength　of　LHPC　at　1d　but　reduced　the　compressive　strength　at　3d　and　7d.　When　0.03　%　DEIPA　and　2　%　gypsum　(3D+2　G　group)　were　co-added,　the　compressive　strength　of　LHPC　was　significantly　improved.　The　compressive　strength　of　LHPC　at　3d　and　7d　reached　23.0　MPa　and　31.7　MPa,　respectively,　which　were　8.49　%　and　12.01　%　higher　than　those　of　the　reference　group　(REF　group).　When　0.03　%　DEIPA　and　3　%　gypsum　(3D+3　G　group)　were　co-added,　the　compressive　strength　of　LHPC　at　3d　and　7d　increased　to　23.5　MPa　and　31.4　MPa,　respectively,　which　were　10.85　%　and　10.95　%　higher　than　that　of　the　REF　group.　After　DEIPA　and　gypsum　were　co-added,　the　hydration　shoulder　peak　of　LHPC　paste　appeared　later　and　broader　compared　with　the　3D　group,　with　a　significant　increase　in　cumulative　heat　release　over　3d.　At　3d　and　7d　of　hydration,　after　co-adding　DEIPA　and　gypsum,　the　amount　of　portlandite　(CH)　generated　increased　compared　with　the　3D　group,　the　content　of　chemically　bound　water　(CBW)　significantly　increased,　and　the　degree　of　hydration　significantly　improved.　The　addition　of　gypsum　further　enhanced　the　effect　of　DEIPA　on　promoting　the　hydration　of　the　ferrite　phase　(C4AF)　in　the　LHPC　paste.　It　alleviated　the　inhibitory　effect　of　DEIPA　on　C3S　hydration,　accelerated　the　formation　of　hydration　product　monosulfoaluminate　(AFm),　optimized　pore　size　distribution,　and　densified　the　microstructure,　effectively　improving　the　early　mechanical　properties　of　LHPC.　This　study　provides　a　new　approach　to　enhance　the　early　reactivity　of　LHPC.　©　2024