Cov nyhuv mechanism ntawm micro silica hmoov ntawm lub zog ntawm kev ua haujlwm siab ua vaj tse

Filling Effect

Thaum npaj cov pob zeb sib tov, cov dej ntxiv feem ntau xav tau kom ua tiav qhov kev xav tau ntawm kev tsim kho. Qhov dej ntxiv no, ntau tshaj qhov xav tau rau cov cement hydration, dilutes cov cement paste thiab tsis muaj zog nws cov khoom sib txuas. Tsis tas li ntawd, cov dej ntau dhau tsim cov voids lossis cov channel hauv cov pob zeb uas, thaum evaporation thaum lub sij hawm hardening, tawm hauv qab pores. Qhov no txo ​​qhov ua haujlwm zoo ntawm qhov chaw ntawm lub pob zeb thiab tuaj yeem ua rau muaj kev ntxhov siab nyob ib puag ncig lub qhov hws hauv qab load. Nyob rau hauv lub pob zeb, cov dej los ntshav sab hauv accumulates hauv qab cov aggregate hais, tsim ntxeem tau interfacial zones. Hauv thaj chaw hloov pauv hloov pauv, ntau Ca(OH)₂ cov ntaub ntawv ntau dua li lwm qhov chaw, nrog cov muaju loj uas nthuav tawm qhov kev sib tw muaj zog sib npaug mus rau qhov sib sau ua ke. Cov loj Ca(OH)₂ crystals sib npaug rau qhov sib sau ua ke yog qhov ua rau tawg thiab tsis muaj zog dua li calcium silicate hydrate (CSH) gel. Qhov ntxeem tau thiab tsis muaj zog sib txuas ntawm qhov kev hloov pauv hauv cheeb tsam, tus yam ntxwv los ntawm kev taw qhia loj Ca(OH)₂ crystals, dhau los ua thaj chaw muaj zog-tsis muaj zog hauv cov pob zeb.

Hauv cov pob zeb ua haujlwm siab (HPC), qhov sib ntxiv ntawm silica fume ua rau muaj zog dua piv rau cov pob zeb uas tsis muaj silica fume. Cov kws tshawb fawb tau suav tias hloov 15% ntawm cov cement nrog silica fume tshwm sim hauv qhov sib piv ntawm kwv yees li 1: 2, 000, 000 ntawm cov cement hais thiab silica fume hais, txhais tau tias ob lab silica fume hais sib haum rau ib qho. cement particle. Qhov no qhia tau hais tias silica fume qhov cuam tshuam loj heev ntawm HPC lub zog. Silica fume, nrog ib txoj kab uas hla 100 npaug me dua li cov cement hais, ua rau cov voids hauv cov cement matrix, zoo ib yam li cov cement hais tias ua li cas rau qhov sib txawv ntawm cov aggregates thiab nplua aggregates sau cov voids ntawm coarse aggregates. Qhov micro-scale densification no nce lub compactness ntawm HPC thiab txhim khu nws lub zog, ib tug tshwm sim hu ua "filling effect" ntawm silica fume. Nyob rau hauv HPC, silica fume txo cov pores nyob rau hauv cov cement paste, tsub kom homogeneity, thiab tswj tag nrho cov porosity.

Cov silica fume nyob rau hauv cov cement-aggregate interfacial hloov chaw yuav txo tau HPC los ntshav, tiv thaiv dej tsub zuj zuj hauv qab cov aggregates. Qhov no ua rau lub microstructure nyob rau hauv qhov kev hloov pauv cheeb tsam uas zoo ib yam li cov cement paste, ua kom lub compactness ntawm interfacial hloov chaw thiab txo nws cov thickness. Cov nplua silica fume particles ua raws li qhov chaw nucleation rau Ca(OH)₂ crystals, ua rau me me thiab ntau randomly oriented crystals. Kev suav nrog silica fume txhim kho lub zog sib txuas ntawm cov cement paste thiab aggregate hauv HPC, tshem tawm "kev sib txuas tsis muaj zog" ntawm cov khoom sib txawv ntawm cov pob zeb sib txawv. Raws li qhov tshwm sim, HPC nthuav tawm cov yam ntxwv ntawm cov khoom siv sib xyaw, nrog cov khoom sib xyaw ua ke ua qhov kev txhawb zog ntau dua li tsuas yog inert fillers. Txawm hais tias silica fume tsis tau txhim kho lub zog ntawm cov cement paste yam tsis muaj kev sib sau ua ke, nws tseem ceeb heev kom muaj zog ntawm cov pob zeb nrog tib cov dej-cement piv, ua rau cov pob zeb muaj zog tshaj qhov muab tshuaj txhuam.

Pozzolanic nyhuv

Thaum lub sij hawm hydration ntawm Portland cement, cov tshuaj tiv thaiv tsim cov khoom siv dej xws li calcium silicate hydrate (CSH) gel, calcium hydroxide (Ca(OH) ₂), thiab ettringite. Ntawm cov no, Ca(OH)₂ muaj kev cuam tshuam rau lub zog. SiO₂ feem ntau dispersed nyob rau hauv silica fume reacts nrog Ca(OH)₂ los tsim ntxiv CSH gel, ib tug tshwm sim hu ua cov nyhuv pozzolanic:

Ca(OH)₂ + SiO₂ + H₂O → CSH

Ntau cov kev tshawb fawb tau pom tias nyob rau hauv lub xub ntiag ntawm silica fume, Ca (OH)₂ tseem ceeb muaj nyob rau hauv cov khoom thaum ntxov hydration ntawm cement. Nyob rau tib lub sijhawm, tus nqi ntawm Ca(OH)₂ txo qis thiab nws thiaj li ua tsis tau. Grutzeck thiab lwm tus tau piav qhia txog cov nyhuv pozzolanic ntawm silica fume raws li hauv qab no: Thaum sib cuag nrog cov dej sib tov, silica fume tsim cov silica-nplua nuj gel uas nqus dej. Cov gel no sib sau ntawm cov cement uas tsis muaj dej, maj mam ntim lawv. Ca(OH)₂ reacts nrog cov silica-nplua nuj gel los tsim CSH gel, uas ua rau cov voids nyob rau hauv cov khoom hydration ntawm cov cement, ua kom cov qauv ntom ntom. Hauv cov ntsiab lus, cov nyhuv pozzolanic ntawm silica fume hloov Ca (OH) ₂, uas cuam tshuam rau lub zog, rau hauv CSH gel, uas ua rau qhov chaw ntawm cov khoom siv cement hydration thiab txhawb HPC lub zog loj hlob. Tsis tas li ntawd, cov tshuaj tiv thaiv ntawm silica fume thiab Ca(OH)₂ siv Ca(OH)₂, ua kom cov cement hydration thiab txhim kho lub zog thaum ntxov ntawm HPC.

Pore ​​Solution Chemical Effect

Hauv cov cement-silica fume hydration system, nce silica fume-to-cement ratio txo ​​Ca / Si piv ntawm cov khoom siv dej. Qhov qis Ca/Si piv tso cai rau CSH gel los tsim cov ions ntxiv, xws li txhuas thiab alkali hlau ions, uas txo cov concentration ntawm alkali hlau ions hauv pore tov. Qhov tshwm sim no yog lub npe hu ua pore tov tshuaj nyhuv. Ntxiv qhov hloov pauv ntawm cov cement nrog silica fume txo cov pH ntawm cov pore tov vim kev noj cov alkali hlau ions thiab Ca(OH)₂ hauv cov tshuaj tiv thaiv nrog silica fume. Rau HPC uas muaj alkali-reactive aggregates, qhov txo qis hauv alkali hlau ion concentration (K⁺, Na⁺) yog qhov tseem ceeb vim nws txo qis lossis tshem tawm qhov kev pheej hmoo ntawm alkali-silica cov tshuaj tiv thaiv (ASR). Silica fume kuj nce HPC qhov kev tiv thaiv thiab txo qis cov tshuaj chloride ion (Cl⁻) nkag mus, tiv thaiv rebar corrosion thiab txhim kho lub zog thiab kav ntev ntawm HPC.