Overview And Mechanism Of Concrete Water-reduced Agent

Superplasticizers yog cov khoom siv tseem ceeb uas tuaj yeem txo cov dej-rau-cement piv ntawm cov pob zeb, yog li txhim kho nws lub zog thiab kav ntev. Superplasticizers tau muab faib ua cov superplasticizers zoo tib yam thiab cov khoom siv hluav taws xob zoo heev. Superplasticizers nrog cov dej txo qis dua 5% tab sis tsawg dua 10% yog cais raws li cov khoom siv zoo tib yam, xws li sodium rosin acid, sodium lignosulfonate, thiab stearic acid xab npum. Superplasticizers nrog cov dej txo qis dua 10% yog cais raws li cov khoom siv ua haujlwm siab, suav nrog melamine-based, naphthalene-based, aminoplast sulfonate-based, hloov lignosulfonate-based, thiab polycarboxylate-based superplasticizers. Ntawm ntau qhov ua tau zoo superplasticizers, polycarboxylate-raws li superplasticizers nrog cov qauv zoo li molecular tau dhau los ua qhov tseem ceeb ntawm kev tshawb fawb hauv tsev thiab thoob ntiaj teb thiab kev txhim kho vim lawv cov dej-txo qis, zoo slump tuav, tsawg npaum li cas, thiab tsis muaj qhov tseem ceeb retardation. .

Cov nyhuv txo dej yog lub luag haujlwm tseem ceeb ntawm surfactants hauv cov txheej txheem cement hydration. Lub superplasticizer yog ib qho khoom ntxiv uas tuaj yeem txo cov dej sib tov yam tsis muaj kev cuam tshuam rau kev ua haujlwm ntawm pob zeb. Xwb, nws tuaj yeem txhim kho kev ua haujlwm ntawm pob zeb tsis hloov cov ntsiab lus dej, lossis nws tuaj yeem ua tiav ob qho tib si yam tsis muaj kev hloov pauv huab cua. Tam sim no, cov superplasticizers siv hauv pob zeb yog tag nrho cov surfactants thiab yog cov anionic surfactants.

Thaum cov cement tov nrog dej, cov tshuaj tiv thaiv hydration tshwm sim, ua rau cov qauv flocculated uas encapsulate ntau cov dej sib tov, uas txo cov kev ua haujlwm (tseem hu ua "workability," hais txog lub peev xwm ntawm cov pob zeb tshiab kom nyob twj ywm, ntom, thiab tsis muaj kev sib cais thaum sib xyaw, kev thauj mus los, thiab nchuav). Yuav kom tswj tau qhov kev ua haujlwm uas yuav tsum tau ua thaum tsim kho, cov dej sib xyaw ntxiv yuav tsum tau ntxiv. Txawm li cas los xij, kev nce hauv cov ntsiab lus dej ua rau muaj qhov pore ntau dhau ntawm cov cement paste, uas cuam tshuam rau lub cev thiab cov khoom siv ntawm cov pob zeb tawv tawv. Yog tias cov dej encapsulated tuaj yeem tso tawm, kev siv dej tuaj yeem txo qis heev. Los ntawm kev sib koom ua ke ntawm qhov tsim nyog ntawm superplasticizer thaum lub sij hawm npaj cov pob zeb, cov nyhuv no tuaj yeem ua tiav zoo.

Tom qab ntxiv superplasticizer rau cov pob zeb, cov pab pawg hydrophobic ntawm superplasticizer adsorb rau saum npoo ntawm cov cement hais, thaum cov pawg hydrophilic taw tes rau cov tshuaj aqueous, tsim cov monolayer lossis multilayer adsorption zaj duab xis. Vim yog qhov taw qhia adsorption ntawm surfactant, qhov saum npoo ntawm cov cement hais yog tib yam nqi. Qhov no ua rau kev sib nrig sib repulsion, uas tsis tsuas yog ua kom cov cement-dej system nyob rau hauv ib qho kev ruaj ntseg ncua kev kawm ntawv tab sis kuj ua rau lub flocculated qauv tsim thaum lub sij hawm thawj zaug ntxiv ntawm dej mus disperse thiab tawg, yog li tso cov dej nyob rau hauv lub flocculated qauv thiab ua tiav kev txo cov dej. Qhov sib ntxiv ntawm superplasticizer tsis tsuas yog txhim kho kev ua haujlwm ntawm cov pob zeb tshiab tab sis kuj tseem txo cov dej-rau-cement piv, ua rau txo qis hauv cov pore ntim hauv cov cement paste, ua rau cov cement denser thiab txhim kho lub zog compressive. Qhov sib ntxiv ntawm superplasticizer kuj cuam tshuam rau cov dej ntawm cov cement thiab lub sijhawm teeb tsa. Cov khoom no yog qhov tseem ceeb hauv kev siv tswv yim. Txawm li cas los xij, thaum lub superplasticizer zoo ua rau cov qauv flocculated thiab tso cov dej dawb sab hauv, nws kuj ua rau tsis muaj kev cuam tshuam ntawm cov cement thiab dej. Los ntawm qhov kev xav no, superplasticizers ib txwm ua rau cov ntshav thiab kev sib cais ntawm kev sib xyaw rau qee qhov, uas yog qhov ua rau muaj qhov tsis xws luag xws li blotches, thiab nyob rau hauv cov xwm txheej hnyav, tuaj yeem ua rau honeycomb nto, network zoo li tawg, los yog yas shrinkage tawg. raws li kev txhawb nqa tuav hauv pob zeb tom qab pouring.