1. Txheej txheem cej luam ntawm cellulose ether (HPMC)
Hydroxypropyl methylcellulose (HPMC) yog ib qho kev siv cellulose ether compound, uas yog hloov kho los ntawm ntuj cellulose. Nws muaj cov dej solubility zoo heev, ua yeeb yaj kiab, ua kom tuab thiab nplaum, yog li nws tau siv dav hauv cov khoom siv hauv tsev. Kev thov ntawm HPMC hauv cov khoom siv cement feem ntau yog los txhim kho nws cov dej ntws, tuav dej thiab kho lub sijhawm teeb tsa.
2.Basic txheej txheem ntawm cement chaw
Cov txheej txheem ntawm cement reacting nrog dej los tsim hydrates yog hu ua hydration reaction. Cov txheej txheem no tau muab faib ua ob peb theem:
Lub sij hawm induction: Cement particles pib yaj, tsim calcium ions thiab silicate ions, qhia lub sij hawm luv luv.
Lub sij hawm acceleration: Cov khoom lag luam dej nce sai thiab cov txheej txheem pib pib.
Lub sij hawm deceleration: Lub hydration tus nqi txo, cement pib harden, thiab cov cement pob zeb yog tsim.
Lub sij hawm ruaj khov: Cov khoom siv dej maj mam loj hlob thiab lub zog maj mam nce.
Lub sijhawm teem sijhawm feem ntau yog muab faib ua lub sijhawm pib thiab lub sijhawm teem sijhawm kawg. Lub sij hawm pib lub sij hawm yog hais txog lub sij hawm thaum cov cement paste pib poob plasticity, thiab lub sij hawm zaum kawg yog hais txog lub sij hawm thaum cov cement paste plam tag nrho plasticity thiab nkag mus rau lub hardening theem.
3. Mechanism ntawm kev cuam tshuam ntawm HPMC ntawm cement teem sij hawm
3.1 Thickening nyhuv
HPMC muaj cov nyhuv thickening tseem ceeb. Nws tuaj yeem ua rau kom cov viscosity ntawm cov cement paste thiab tsim kom muaj cov viscosity siab. Cov nyhuv thickening no yuav cuam tshuam rau dispersion thiab sedimentation ntawm cov cement hais, thiab yog li cuam tshuam rau kev nce qib ntawm cov tshuaj tiv thaiv hydration. Cov nyhuv thickening txo cov deposition tus nqi ntawm hydration khoom nyob rau saum npoo ntawm cement hais, yog li ncua lub sij hawm teem.
3.2 Kev tuav dej
HPMC muaj peev xwm tuav tau dej zoo. Ntxiv HPMC rau cement paste tuaj yeem txhim kho cov dej khaws cia ntawm cov tshuaj txhuam. Kev tuav dej siab tuaj yeem tiv thaiv cov dej ntawm cov cement los ntawm evaporating sai heev, thiaj li tswj cov dej ntsiab lus hauv cov cement paste thiab ntev lub sij hawm ntawm cov tshuaj tiv thaiv hydration. Tsis tas li ntawd, cov dej tuav cia pab cov cement paste tswj cov av noo kom zoo thaum lub sijhawm kho thiab txo qhov kev pheej hmoo ntawm kev tawg los ntawm kev poob dej thaum ntxov.
3.3 Hydration retardation
HPMC tuaj yeem tsim cov yeeb yaj kiab tiv thaiv npog qhov chaw ntawm cov cement, uas yuav cuam tshuam cov tshuaj tiv thaiv dej. Cov yeeb yaj kiab tiv thaiv no tiv thaiv kev sib cuag ncaj qha ntawm cov cement thiab dej, yog li ncua cov txheej txheem dej ntawm cov cement thiab ua kom lub sijhawm teem sijhawm. Qhov kev ncua sij hawm no tshwj xeeb yog pom tseeb hauv qhov hnyav molecular HPMC.
3.4 Txhim kho thixotropy
Qhov sib ntxiv ntawm HPMC tuaj yeem txhim kho cov thixotropy ntawm cov cement slurry (piv txwv li, fluidity nce nyob rau hauv qhov kev txiav txim ntawm sab nraud quab yuam thiab rov qab mus rau qhov qub qub tom qab lub zog sab nraud raug tshem tawm). Cov cuab yeej thixotropic no pab txhim kho kev ua haujlwm ntawm cov cement slurry, tab sis nyob rau hauv cov nqe lus ntawm kev teeb tsa lub sij hawm, qhov kev txhim kho thixotropy no yuav ua rau cov slurry rov faib nyob rau hauv shear quab yuam, ntxiv rau ncua sij hawm teem caij.
4. Kev siv lub tswv yim ntawm HPMC cuam tshuam rau lub sijhawm teeb tsa cement
4.1 Self-leveling cov ntaub ntawv hauv pem teb
Hauv cov ntaub ntawv hauv pem teb tus kheej, cov cement xav tau lub sijhawm pib pib ntev dua rau kev ua haujlwm ntawm qib thiab screeding. Ntxiv HPMC tuaj yeem ncua lub sijhawm pib ntawm cov cement, tso cai rau cov khoom siv tus kheej kom muaj lub sijhawm ua haujlwm ntev dua thaum tsim kho, zam qhov teeb meem tshwm sim los ntawm kev teeb tsa ntxov ntawm cov cement slurry thaum tsim kho.
4.2 Premixed mortar
Hauv cov mortar premixed, HPMC tsis tsuas yog txhim kho cov dej tuav ntawm mortar, tab sis kuj ua rau lub sijhawm teem sijhawm. Qhov no yog ib qho tseem ceeb tshwj xeeb tshaj yog rau lub sijhawm uas muaj kev thauj mus los ntev thiab siv sijhawm ntev, kom ntseeg tau tias lub mortar tswj kev ua haujlwm zoo ua ntej siv thiab zam kev tsim teeb meem los ntawm lub sijhawm luv luv.
4.3 Dry-mixed mortar
HPMC feem ntau tau ntxiv rau cov khib nyiab qhuav los txhim kho nws cov kev tsim kho. Cov nyhuv thickening ntawm HPMC nce lub viscosity ntawm mortar, ua rau nws yooj yim rau kev thov thiab theem thaum lub sij hawm tsim kho, thiab tseem ncua lub sij hawm teem, muab cov neeg ua hauj lwm tsim lub sij hawm txaus los hloov kho.
5. Cov yam ntxwv cuam tshuam rau lub sijhawm teeb tsa ntawm cov cement los ntawm HPMC
5.1 HPMC tus nqi ntxiv
Tus nqi ntawm HPMC ntxiv yog qhov tseem ceeb cuam tshuam rau lub sijhawm teeb tsa ntawm cov cement. Feem ntau, qhov ntau dua ntawm HPMC ntxiv, qhov pom tseeb dua qhov kev ncua sij hawm ntawm cov cement. Qhov no yog vim ntau HPMC molecules tuaj yeem npog ntau cov cement particle qhov chaw thiab cuam tshuam cov dej tshuaj tiv thaiv.
5.2 Molecular hnyav ntawm HPMC
HPMC ntawm qhov sib txawv molecular hnyav muaj qhov sib txawv ntawm lub sijhawm teeb tsa ntawm cov cement. HPMC nrog qhov hnyav molecular feem ntau muaj cov nyhuv thickening thiab cov dej tuav, yog li nws tuaj yeem ua kom lub sijhawm teem sijhawm ntau dua. Txawm hais tias HPMC nrog qhov hnyav molecular kuj tseem tuaj yeem ua kom lub sijhawm teem sijhawm, cov nyhuv kuj tsis muaj zog.
5.3 Ib puag ncig tej yam kev mob
ambient kub thiab av noo kuj yuav cuam tshuam cov nyhuv ntawm HPMC ntawm cement teem lub sij hawm. Nyob rau hauv ib puag ncig kub, cement hydration cov tshuaj tiv thaiv yog nrawm, tab sis cov khoom tuav dej ntawm HPMC ua rau cov nyhuv no qeeb. Nyob rau hauv ib puag ncig uas tsis muaj qhov kub thiab txias, cov tshuaj tiv thaiv hydration nws tus kheej qeeb, thiab cov nyhuv thickening thiab dej tuav ntawm HPMC tuaj yeem ua rau cov cement teeb lub sij hawm ntev heev.
5.4 Dej-cement ratio
Kev hloov pauv hauv dej-cement piv kuj tseem yuav cuam tshuam cov txiaj ntsig ntawm HPMC rau lub sijhawm teem caij cement. Ntawm qhov sib piv ntawm cov dej-cement ntau dua, muaj dej ntau dua hauv cov cement paste, thiab cov dej tuav ntawm HPMC tuaj yeem cuam tshuam tsawg dua rau lub sijhawm teem. Ntawm qhov qis dej-cement piv, cov nyhuv thickening ntawm HPMC yuav pom tseeb dua, thiab cov txiaj ntsig ntawm kev ncua sij hawm teeb tsa yuav tseem ceeb dua.
Raws li ib qho tseem ceeb ntawm cov cement additive, HPMC cuam tshuam rau lub sij hawm ntawm cov cement los ntawm ntau yam txheej txheem xws li thickening, dej tuav, thiab retardation ntawm hydration cov tshuaj tiv thaiv. Daim ntawv thov ntawm HPMC tuaj yeem ncua lub sijhawm pib thiab zaum kawg ntawm cov cement, muab lub sijhawm ua haujlwm ntev dua, thiab txhim kho kev ua haujlwm ntawm cov khoom siv cement. Hauv kev siv tswv yim, yam xws li cov nyiaj HPMC ntxiv, qhov hnyav molecular, thiab ib puag ncig ib puag ncig sib koom ua ke txiav txim siab nws cov txiaj ntsig tshwj xeeb ntawm lub sijhawm teeb tsa cement. Los ntawm kev hloov kho cov xwm txheej no, kev tswj xyuas meej ntawm cov cement teeb tsa lub sijhawm tuaj yeem ua tiav kom tau raws li qhov xav tau ntawm cov haujlwm sib txawv.
Post lub sij hawm: Jun-21-2024