Abstract
An ability of aluminum-bearing substances-amorphous aluminum hydroxide, aluminum sulphate and basic aluminum sulphate to mitigate alkali-silica reactions in Portland cement mortars has been studied. At equivalent dosages in terms of Al2O3, these substances are ranged in the following order in respect of inhibiting effect: Al(OH)1.78(SO4)0.61 ≥ Al2(SO4)3 > Al(OH)3. It is found that the plasticizing agents of the main types used in cement compositions have no influence on the inhibiting effect of aluminum-bearing admixtures. To control the setting time of cement paste, iron(II) sulphate may be used for partial substitution of Al2SO4·18H2O, and this operation is not influence on the results of ASR expansion test.
Highlights
The presence of reactive SiO2-inclusions in fine and coarse aggregates is one of the factors that negatively affect the durability of concrete
The interaction of reactive SiO2 with alkalis coming into pore fluid from outside or from the concrete mix components leads to the formation of the products causing significant internal tense stressses and destructive deformations of concrete [1]
2) At equivalent dosages in terms of Al2O3, these substances are ranged in the following order in respect of inhibiting effect: Al(OH)1.78(SO4)0.61 ≥ Al2(SO4)3 > Al(OH)3
Summary
The presence of reactive SiO2-inclusions in fine and coarse aggregates is one of the factors that negatively affect the durability of concrete. The widely used way to prevent alkali-silica reactions (ASR) is the introducing of pozzolanic additives-silica fume, metakaolin, fly-ash, ground granulated blast furnace slag—into concrete mix [2] [3]. These additives exhibit efficacy as inhibitors of ASR at dosages of 15% - 50% by weight of cement.
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