Kev Tshawb Fawb Txog Dej-txo Mechanism Ntawm Polycarboxylate Superplasticizers

Kev tshawb fawb txog Dej-txo Mechanism ntawm Polycarboxylate Superplasticizers

Nrog rau txoj kev loj hlob ntawm lub teb chaws kev lag luam thiab lub cib fim coj los ntawm Tuam Tshoj txoj kev nkag mus rau hauv WTO, kev tsim kho ntawm ntau lub tsev loj loj hauv cov nroog thiab txawm tias nyob hauv lub teb chaws, kev tsim kho cov choj thiab txoj kev loj, thiab kev txhim kho. ntawm cov chaw tsheb thauj mus los hauv nroog, thiab lwm yam. Qhov kev thov rau kev npaj yog ntau thiab ntau, thiab cov kev xav tau ntawm nws tau dhau los ua ntau thiab xav tau. Raws li ib feem tseem ceeb ntawm kev ua haujlwm siab ua vaj tse, superplasticizer tau them nyiaj ntau dua los ntawm cov kws tsim khoom thiab cov kws tshaj lij. Nyob rau hauv kev ua liaj ua teb niaj hnub cov ntaub ntawv thiab thev naus laus zis, muaj ob peb txoj hauv kev los tsim cov pob zeb zoo yam tsis muaj kev siv cov khoom sib xyaw. Tam sim no, feem ntau ntawm cov lag luam dej txo qis muaj qee qhov tsis txaus ntawm ib txoj kev lossis lwm qhov. Nws yog tam sim no los tsim ib tus neeg saib xyuas dej-txo kom muaj txiaj ntsig zoo nrog tus nqi qis thiab cov txiaj ntsig zoo, thiab nws txoj kev cia siab rau kev lag luam thiab daim ntawv thov tus nqi yog qhov ntsuas tsis tau.

Lub polycarboxylate series, hu ua lub thib peb tiam superplasticizer, muaj daim ntawv thov kev cia siab zoo tshaj plaws thiab kev ua tau zoo tshaj plaws. Nws cov txiaj ntsig tseem ceeb suav nrog: cov dej txo qis yog siab li 30 feem pua ​​~ 40 feem pua, uas tuaj yeem ua rau kev ua haujlwm ntawm cov cement thiab cov ntaub ntawv cementitious mus txog lub xeev zoo tshaj plaws; hardly retard qhov chaw tab sis tuav lub slump ntawm pob zeb (tsawg dua 1 hauv 1 teev). cm); tuaj yeem siv nrog ntau hom cement, pozzolan thiab lwm yam khoom siv; tuaj yeem nce cov hmoov tshauv ya thiab av slag uas tuaj yeem hloov Portland cement.

Thaum npaj cov pob zeb, qhov sib piv ntawm cov cement thiab dej (dej-cement ratio) yog qhov tsis sib xws. Tag nrho cov khoom siv cementitious hauv kev ua haujlwm siab ua vaj tse yuav nce, yog li cov dej xav tau yuav nce ntxiv. Ntawm qhov tod tes, txhawm rau txhim kho compactness thiab lub zog, cov dej-cement piv yuav tsum tau txo. Qhov tshwm sim ntawm kev nce tus nqi ntawm cov cement thiab txo cov dej-cement piv yog tias cov viscosity ntawm cov pob zeb nce thiab cov rheology ua phem. Tam sim no, txoj hauv kev zoo tshaj plaws thiab muaj tseeb los daws qhov kev tsis sib haum xeeb saum toj no yog siv cov dej ua haujlwm siab kom txo tau tus neeg sawv cev. Daim ntawv no npaj siab yuav ua kom ntxaws ntxaws los ntawm cov dej txo cov txheej txheem, cov qauv molecular thiab tshuaj ua haujlwm ntawm cov dej txo tus neeg sawv cev hauv cov cement thiab lwm yam cuam tshuam.

Dej txo mechanism

Feem ntau ntawm cov superplasticizers yog anionic surfactants, uas yog tov rau hauv cov cement slurry thiab adsorbed rau saum npoo ntawm cov cement hais, thiab dissociated rau hauv organic anionic pawg nrog hydrophilic thiab lipophilic. Rau naphthalene-raws li superplasticizers, Zeta muaj peev xwm feem ntau yog siv los qhia qhov loj ntawm qhov tawg. Feem ntau, qhov loj dua Zeta muaj peev xwm tus nqi, qhov ntau dua qhov electrostatic repulsion ntawm cov cement hais, thiab qhov tseem ceeb ntawm cov nyhuv dispersion. Rau polycarboxylate superplasticizers, Zeta muaj peev xwm tus nqi qis (tsuas yog -10 ~ -15 mv), tab sis cov cement paste kuj muaj qhov zoo heev dispersibility thiab poob qis me me. Yog li ntawd, yuav tsum muaj lub tshuab tshiab los piav qhia txog cov dej txo cov nyhuv ntawm polycarboxylate superplasticizers. Tam sim no lees txais "steric hindrance theory" los piav txog cov txheej txheem ntawm polycarboxylate superplasticizers yog lub zog qis tshaj plaws.

Nws feem ntau ntseeg tias tus yuam sij rau cov dej txo cov nyhuv ntawm polycarboxylate superplasticizers yog cov nyhuv anionic tsim los ntawm pawg carboxyl ntawm cov saw hlau macromolecular thiab cov nyhuv steric hindrance ntawm cov saw ntev ntawm nruab nrab polyoxyethylene.

Hais txog cov dej-txo cov txheej txheem ntawm polycarboxylate superplasticizers, Morin ntseeg hais tias muaj electrostatic nqi ntawm cov cement hais, thiab ib feem ntawm cov nqi zoo yog neutralized los ntawm tus nqi dawb hauv huab cua, tab sis tus nqi tsis zoo tseem nyob hauv lub xeev tsis sib npaug. . Thaum tsis muaj superplasticizers, cov nqi tsis zoo yog tiv thaiv los ntawm txheej cationic (calcium ions), ua ib txheej hu ua ob-ion txheej. Thaum qhov kev ncua deb ntawm cov khoom yog ntau dua qhov kev ncua deb ntawm ob txheej ion, lub electrostatic shielding quab yuam yog qhov tseem ceeb. Obviously, nruab nrab particles agglomerate vim cov nyhuv ntawm nto nro thiab ploj ntawm electrostatic repulsion, thiab fluidity ntawm cov cement slurry yog tsawg heev. Tom qab ntxiv cov superplasticizer, macromolecular chains ntawm superplasticizer adsorbed rau saum npoo ntawm cov cement hais tuaj yeem maj mam txo cov concentration ntawm cov ions zoo nyob ze ntawm cov khoom tsis zoo, yog li ua kom cov nyhuv ntawm cov txheej thaiv thaiv. Qhov ntau ntawm kev quab yuam ntawm cov khoom kuj nce ntxiv. Zuag qhia tag nrho, cov electrostatic repulsion tseem muaj thiab disperses cov hais. Tsis tas li ntawd, thaum cov dej txo tus neeg sawv cev txo qhov nro saum npoo, qhov adhesion ntawm cov khoom los ntawm qhov nro saum npoo kuj txo.

Polycarboxylate superplasticizer macromolecular chains feem ntau grafted nrog ntau pab pawg, xws li polyoxyethylene chains nrog ib tug ntev, carboxyl pawg, sulfonic acid pawg, -COOH thiab -SO3Na, thiab lwm yam., uas muaj peev xwm disperse thiab disperse cement hais. Mobility-acting polar pawg. Nws yog qhov tseeb vim tias cov txiaj ntsig ntawm cov pab pawg ua haujlwm saum toj no hais tias polycarboxylate superplasticizer muaj cov dej-txo cov txheej txheem sib txawv ntawm lwm cov superplasticizers. Tsis tsuas yog cov dej txo cov nyhuv yog pom tseeb, tab sis kuj yog qhov poob qis me me (tsawg dua 1cm hauv 1 teev). Cov proportions thiab chain lengths ntawm ntau pab pawg muaj kev cuam tshuam zoo rau dispersibility ntawm superplasticizer.