Introduction　Steel　slag　is　a　solid　waste　produced　from　steelmaking,　which　has　a　potential　cementitious　activity.　However,　its　cementitious　activity　is　much　lower　than　that　of　Portland　cement.　Mechanical　grinding,　acid　activation,　alkali　activation,　high-temperature　curing,　modification/reconstruction　and　organic　activation　methods　are　commonly　used　to　improve　the　hydraulic　activity　of　steel　slag.　Triethanolamine　is　commonly　used　as　an　organic　admixture　to　improve　cementitious　activity　of　steel　slag.　The　existing　research　on　the　hydration　of　TEA　on　steel　slag　still　focuses　on　a　steel　slag-cement　composite　system,　in　which　the　proportion　of　cement　is　higher　and　the　hydration　rate　is　faster,　so　the　results　obtained　are　related　to　cement　hydration,　and　it　is　difficult　to　characterize　the　effect　of　TEA　on　steel　slag.　It　is　thus　necessary　to　investigate　the　hydration　of　pure　steel　slag　in　the　presence　of　triethanolamine.　In　this　paper,　the　hydration　characteristics　of　pure　steel　slag　under　the　complexation　of　TEA　were　characterized　by　compressive　strength,　heat　of　hydration,　thermogravimetry,　phase　analysis,　complexation　ability　and　dissolution　characteristics　as　well.　Methods　The　compressive　strength　of　hardened　steel　slag　paste　was　tested.　In　this　work,　the　hydration　characteristics　of　steel　slag　were　investigated　at　different　TEA　concentrations,　and　the　concentrations　selected　were　0,　500,　1　000　mg/L　and　2　000　mg/L.　A　mass　ratio　of　TEA　solution　to　steel　slag　was　kept　at　0.35.　The　size　of　test　block　was　20　mm×20　mm×20　mm,　and　the　curing　age　was　3,　7　d　and　28　d.　In　the　process　of　compressive　strength　testing,　the　test　entrance　force　was　set　to　be　200　N,　and　the　pressure　was　applied　by　force　control,　and　the　pressure　rate　was　100　N/s.　After　the　compressive　strength　was　tested,　the　specimens　were　smashed　(＜5　mm)　and　the　center　portion　of　the　specimens　was　immersed　in　an　isopropanol　solution　to　terminate　hydration,　and　the　terminated　hydrated　steel　slag　pieces　were　dried　in　a　vacuum　drying　oven　at　40　℃.　After　drying,　steel　slag　pieces　were　ground　and　sieved　through　a　200　mesh　(74　μm)　sieve.　A　portion　of　steel　slag　powder　was　taken　for　thermogravimetric　analysis　and　X-ray　diffraction　(XRD).　The　hydration　heat　of　steel　slag　paste　was　determined　using　calorimetry,　and　the　exothermic　process　of　hydration　was　recorded　from　the　addition　of　water　or　TEA　solution　for　72　h.　The　TEA　solution　concentration　and　its　ratio　to　steel　slag　both　were　consistent　with　the　tests　of　compressive　strength.　The　complexation　ability　of　TEA　with　different　metal　ions　was　determined　by　a　conductivity　method.　The　complexation　ability　of　TEA　with　metal　ions　was　characterized　via　continuously　adding　TEA　to　a　solution　of　metal　ions　at　the　same　concentration　and　recording　the　conductivity　data.　The　conductivity　method　was　also　used　to　characterize　the　dissolution　process　of　steel　slag　in　the　presence　or　absence　of　TEA.　The　conductivity　of　solution　without　steel　slag　was　the　initial　value,　which　was　measured　from　the　contact　of　steel　slag　with　water　and　recorded　continuously　for　25　min.　Results　and　discussion　The　compressive　strength　of　hardened　steel　slag　paste　with　TEA　is　higher　than　that　of　the　blank　group　without　TEA　at　each　age.　This　indicates　that　TEA　can　simultaneously　increase　the　early　and　late　compressive　strength　of　hardened　steel　slag　paste,　and　this　strengthening　effect　increases　with　the　increase　of　TEA　concentration.　When　TEA　is　in　steel　slag　paste,　the　diffraction　peaks　of　monocarboaluminate　(Mc)　appear,　and　the　diffraction　peaks　of　C2F　gradually　become　weaker.　This　indicates　that　TEA　can　promote　the　formation　of　Mc,　and　the　content　of　CaCO3　is　fixed　at　different　TEA　concentrations,　so　it　can　be　inferred　that　TEA　promotes　the　formation　of　Mc　via　promoting　the　hydration　of　aluminum　phases.　Meanwhile,　TEA　promotes　the　hydration　of　C2F,　and　[Fe]　in　C2F　can　participate　in　the　formation　of　Mc　as　a　substitutional　ion　of　[Al]　to　form　(C4　(A,　F)CH11)　.　The　heat　of　hydration　and　thermogravimetric　tests　further　indicate　that　TEA　can　promote　the　hydration　of　aluminate　and　ferrate　phases.　The　hydration　degree　is　enhanced　by　the　formation　of　a　large　amount　of　Mc.　The　increase　in　hydration　degree　ultimately　leads　to　an　increase　in　compressive　strength.　The　promotion　of　Mc　formation　by　TEA　is　related　to　its　complexation.　When　the　concentration　of　TEA　is　less　than　or　equal　to　0.05　mol/L,　i.e.,　the　molar　ratio　of　TEA　to　metal　ions　is　less　than　or　equal　to　1,　the　complexation　ability　of　TEA　on　Fe3+　is　stronger　than　that　of　Al3+　and　Ca2+.　When　the　concentration　of　TEA　is　greater　than　or　equal　to　0.05　mol/L,　i.e.,　the　molar　ratio　of　TEA　to　metal　ions　is　greater　than　or　equal　to　1,　the　complexation　ability　of　TEA　on　Al3+　is　stronger　than　that　of　Fe3+　and　Ca2+.　TEA　promotes　the　dissolution　of　mineral　phase　in　steel　slag　through　complexation.　The　free-moving　metal　ions　and　the　complexed　metal　ions　in　liquid　phase　of　steel　slag　can　simultaneously　participate　in　the　precipitation　reaction　of　hydration　product,　producing　a　large　amount　of　Mc,　and　thus　improving　the　early　and　late　hydration　of　steel　slag　paste,　which　in　turn　manifests　itself　as　an　increase　in　the　compressive　strength.　Conclusions　The　complexation　ability　between　TEA　and　metal　ions　and　effect　of　TEA　complexation　on　dissolution　and　hydration　characteristics　of　pure　steel　slag　were　investigated.　TEA　significantly　increased　the　early　and　late　compressive　strength　of　hardened　steel　slag　paste.　The　main　reason　for　the　increase　in　compressive　strength　of　hardened　steel　slag　paste　was　that　TEA　improved　the　hydration　degree　of　steel　slag　paste　in　early　and　late　stages.　TEA　promoted　the　hydration　of　aluminate　phases　(C3A,　C12A7)　and　ferrate　phase　(C2F),　and　through　the　interaction　with　carbonate,　a　large　number　of　(C4　(A,　F)CH11)　were　formed,　and　the　formation　of　such　hydration　products　was　the　main　reason　for　the　improvement　of　the　hydration　degree　and　the　compressive　strength　of　steel　slag　paste.　The　large　formation　of　Mc　was　related　to　the　complexation　and　solubilization　effect　of　TEA.　TEA　could　complex　with　Ca2+,　Al3+　and　Fe3+,　and　the　complexation　of　TEA　promoted　dissolution　of　steel　slag　and　formation　of　metal　ions　that　could　participate　in　the　precipitation　reaction,　thus　promoting　the　hydration　of　steel　slag　paste.　©　2024　Chinese　Ceramic　Society.　All　rights　reserved.