chapter  6
14 Pages

Frost/salt scaling and ice formation of concrete: Effect of curing temperature and silica fume on normal and high strength concrete

Abstract The presen t experiment s wer e carrie d ou t t o determin e th e consequence s o f th e temperature an d moisture histories for the ice formation and frost/salt scaling resistance of concrete. Non-airentraine d concrete mixe s with W/(C+S) = 0.30 and 0.45, both with and withou t 8 % silic a fume , wer e tested . Th e result s sho w tha t elevate d curin g temperatures (60 °C) drastically increase the scaling for the two W/(C+S) = 0.45 mixes, regardless of the earl y temperature history . (The period at 20 ° C before heatin g t o 6 0 °C wa s varie d from 0 t o 7 hours) . 4 0 ° C gives a smalle r increas e in scaling. For th e W/(C+S) = 0.3 0 mixe s th e effect s o f elevate d curin g temperature s ar e muc h les s pronounced, an d th e leve l o f scalin g muc h lowe r eve n afte r a dry/r e wet-treatment before testing . Silica fume reduces the scalin g for both W/(C+S) - ratios and al l curing procedures. Lo w temperature calorimetr y has show n tha t ic e formation down to - 2 0 °C is very small for concretes with W/(C+S) = 0.30 an d S/(C+S) = 0.08 bot h for 20° C and 6 0 °C curing. Concrete wit h w/ c = 0.30 withou t SF showe d somewha t mor e iceformation bot h afte r 6 0 ° C and 2 0 ° C curing. The result s showe d tha t hig h strengt h concrete wit h silic a fume ca n b e frost/sal t resistan t withou t air entrainment , an d th e results suppor t earlie r findings , that ther e is at leas t a qualitative correlation betwee n ice formation and frost/salt scaling of concrete. Keywords: concrete, durability , frost/salt scaling, heat curing, silica fume, ice formatio n

1 Introductio n

Measurements o f ice formation in water saturate d hardene d cemen t past e (HCP ) ha s shown that bot h drying/rewetting [1,2] and curing at elevated temperature s [3] lead to substantial increase s i n ic e formatio n a s measure d i n a low-temperatur e scannin g calorimeter. The test [3] was performed o n HCP with W/(C+S) = 0.40 an d 0 and 8 %

silica fume (SF) . The ic e formatio n increased wit h increasin g curin g temperature an d decreased with the addition of SF.