Hnub Kawg:14,Mar,2022

Ib qho admixture txhais tau tias yog cov khoom siv uas tsis yog dej, sib sau ua ke, cov khoom siv hydraulic cementitious lossis fiber reinforcement uas yog siv los ua cov khoom xyaw ntawm cov cementitious sib tov los hloov nws cov khoom sib xyaw tshiab, teeb tsa lossis cov khoom tawv tawv thiab ntxiv rau cov khoom ua ntej lossis thaum sib tov. . Raws li tau sau tseg hauv Tshooj 1, cov tshuaj siv tshuaj lom neeg feem ntau txhais tau hais tias yog nonpozzolanic (tsis tas yuav tsum tau calcium hydroxide los ua kom hnov ​​​​mob) admixture nyob rau hauv daim ntawv ntawm cov kua, ncua kev kawm ntawv los yog dej-soluble khoom.

Cov dej-txo cov khoom siv txhim kho cov pob zeb ntawm cov yas (ntub) thiab cov khoom tawv tawv, thaum cov txheej txheem tswj cov khoom siv yog siv rau hauv cov pob zeb uas tau muab tso rau hauv thiab ua tiav rau lwm yam uas tsis yog qhov kub zoo. Ob leeg, thaum siv kom tsim nyog, pab txhawb rau kev coj ua zoo. Tsis tas li ntawd, ob qho tib si sib xyaw yuav tsum ua tau raws li cov cai ntawm ASTM C 494 (saib Table 1).

Dej-txo cov khoom xyaw

Cov dej reducers ua qhov tseem ceeb uas: txo cov dej sib xyaw kom tau txais cov slump. Qhov no tuaj yeem ua rau txo qis ntawm cov dej-cementitious ratio (w / c ratio), uas ua rau kom muaj zog ntxiv thiab ruaj khov ntau dua.

Kev txo qis w / c piv ntawm cov pob zeb tau pom tias yog qhov tseem ceeb tshaj plaws los ua kom ruaj khov, zoo pob zeb. Ntawm qhov tod tes, qee zaum cov cement cov ntsiab lus yuav raug txo qis thaum tswj hwm tus thawj w / c piv los txo cov nqi lossis cov cua sov ntawm cov dej rau cov pob zeb loj.

Dej-txo admixtures kuj txo cov kev sib cais thiab txhim kho cov dej ntws ntawm cov pob zeb. Yog li ntawd, lawv feem ntau yog siv rau kev siv cov pob zeb siv thiab.

Dej-txo admixtures feem ntau poob rau hauv peb pawg: qis-, nruab nrab- thiab siab-ntau. Cov pab pawg no yog nyob ntawm qhov ntau ntawm cov dej txo qis rau cov khoom sib xyaw. Qhov feem pua ​​​​ntawm cov dej txo yog txheeb ze rau cov dej sib xyaw qub uas yuav tsum tau ua kom tau txais ib qho kev poob qis (saib Table 2).

Txawm hais tias txhua tus dej reducers muaj qhov sib xws, txhua tus muaj daim ntawv thov tsim nyog uas nws yog qhov zoo tshaj plaws. Table 3 nthuav qhia cov ntsiab lus ntawm peb hom kev siv dej txo qis, lawv qhov kev txo cov dej thiab lawv cov kev siv tseem ceeb. Lawv cov txiaj ntsig ntawm huab cua nkag mus yuav txawv nyob ntawm chemistry.

Lawv ua haujlwm li cas

Thaum cov cement los ntawm kev sib cuag nrog dej, qhov sib txawv ntawm cov hluav taws xob sib txawv ntawm qhov chaw ntawm cov cement particles nyiam ib leeg, uas ua rau flocculation lossis pawg ntawm cov khoom. Ib feem zoo ntawm cov dej yog absorbed nyob rau hauv cov txheej txheem no, yog li ua rau ib tug cohesive mix thiab txo slump.

Dej-txo admixtures tseem ceeb neutralize nto tsub nqi ntawm cov khoom hais thiab ua rau txhua qhov chaw nqa zoo li nqi. Txij li cov khoom zoo li cov nqi sib tw, lawv txo qis flocculation ntawm cov cement hais thiab tso cai rau kom zoo dua dispersion. Lawv kuj txo cov viscosity ntawm paste, uas ua rau muaj kev poob qis dua.

Table 4 nthuav qhia qee cov ntaub ntawv siv ntau tshaj plaws siv rau txhua qhov ntawm cov dej reducer. Lwm cov khoom siv kuj tseem ntxiv nyob ntawm cov khoom thiab cov chaw tsim khoom. Qee cov dej-txo cov khoom siv muaj cov teebmeem thib ob lossis ua ke nrog cov retarders lossis accelerators.