The Role of Alkalis in Hydraulic Mixtures

Lukáš Prochazka; Jana Boháčová

doi:10.4028/www.scientific.net/MSF.955.62

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HomeMaterials Science ForumMaterials Science Forum Vol. 955The Role of Alkalis in Hydraulic Mixtures

The Role of Alkalis in Hydraulic Mixtures

Abstract:

Alkali substances are present in cements used as a binder in concrete only in a minimum content. The most known process that alkali causes is the alkali-silica reaction. In this reaction, the alkali contained in the cement or supplied from the outside with an inappropriately selected aggregate containing amorphous SiO₂. This reaction results in the development of hydration products, resulting in an increase in the volume of the original components, which can cause a breakage of the concrete structure and subsequent disintegration. The range of alkali-silica reaction can be reduced by the use of a suitable aggregate or the use of Type II admixtures which are characterized by pozzolanic or latently hydraulic activity. These admixtures react with alkali and then no longer react with the amorphous SiO₂ contained in the aggregate. Alkalis also affect other properties of concrete such as basic physical-mechanical properties, frost resistance and pH.In the experimental part the pH values were compared between mixtures of Portland cement and alkaline activated blast furnace slag using slag aggregate from the heap Koněv.

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Periodical:

Materials Science Forum (Volume 955)

Pages:

62-67

DOI:

https://doi.org/10.4028/www.scientific.net/MSF.955.62

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Online since:

May 2019

Authors:

Lukáš Prochazka, Jana Boháčová*

Keywords:

Alkalis, Cement, Concrete, Hydraulic Mixtures, Slag

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* - Corresponding Author

References

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