The change in reactivity of silicate anions during the hydration of calcium silicates and cement

• Published in: Cement and concrete research Vol. 3; no. 6; pp. 767 - 776
• Main Authors: Tamás, Ferenc D., Fábry, Mária
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1973
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/0008-8846(73)90010-0

The change in reactivity of the silicate anion complex of tricalcium silicate, β-dicalcium silicate and portland cement during hydration was studied by measuring the rate constant ( k ) of the silicomolybdic acid formation. The three anhydrous starting materials have identical k values indicating their identical monosilicate anion structure. During hydration the value of k decreases continuously; the rate of decrease of k is highest in case of cement and lowest in case of β-dicalcium silicate. The decrease of k can be attributed to the formation of bridging oxygen ions in the silicate complex. k tends to reach a final, limiting value; beyond this k can still be decreased by special techniques as e.g. by regrinding and rehydrating the hardened samples. Изyyaлocь измeнeниe peaкциoннoя cпocoбнocти cиликaтныч aниoнoв тpeчкaлъциeвoгo cиликaтa, β - дбyчкaльциeбoгo cиликaтa и пopтлqндцeмeнтa б пpoцecce гидpaтaции пaтeм oпpeдeлeния кoнcтaнt cкopocти peaкция (к) фopмиpoвaния из нич cиликo-мoлибдeнoвoя киcлoты. Для нeгидpaтиpoвaнныч вeщecтв знayeния “к” идeнтиyны. yтo cвидeтeльcтвyeт o тoм, yтo aниoннaя cтpyктypa ич oдинaкoвaя (мoнocиликaтнaя). B чoдe гидpaтaции вeлиyинa “к” пocтeпeннo yмeньшaeтcя, пpиyeм нaибoлъшee yмeнъшeниe нaблюдaeтcя в cлyyae пopтдaндцeмeнтa, a нaимeнъee - в cлyyae β - двyчкaльциeвoгo cиликaтa. Taкoe cнижeниe вeлиyны “к” дoлжнo пpипиcывaтьcя oбpaзoвaнию мocтoвыч киcлopoдныч иoнoв в cиликaтнoм кcмплeкce. Beлиyинa “к” cтpeмитcя к нeкoтopoмy пocтoяннoмy знayeнию; дaльнeяшee cнижeниe “к” мoжeт дocтигaтьcя нaпpимep пoвтopным пoмoлoм зaтвepдeвшич oбpaзцoв c пocлeдyющeя втopиyнoя ич гидpaтaциeя.