Volume of ice is about 10% greater than corresponding volume of water!
This causes a lot of problems in areas with extreme weathers. During the winters, water in the pores of concrete freezes. The ice formed occupies larger volume and hence exerts pressure. During the summer, the ice melts, and in the next winter, the pore water freezes again. This cycle is called freezing and thawing of concrete. The pressure developed usually causes surface scaling.

To overcome the ill effects of freeze thaw cycles, air entrainment in concrete was developed. Microscopic air bubbles were introduced in concrete. These bubbles give room for the ice formed to expand without exerting pressure on the concrete.

[The dark areas in the picture above are air bubbles, the lighter areas are coarse aggregates, suspended in a cement mortar]

Air entrainment has the following effects on concrete:

• Resistant to freezing and thawing
• Improved workability and durability
• Decrease in strength

A thorough literature survey on the topic by reading research papers will set you up for a project on the topic.

A project on the topic may involve one or more of the following:

• improving the strength of air entrained concrete,
• further increase in workability and/or durability,
• using alternative materials in air entrained concrete and studying its effects on the concrete

Calcestruzzo impregnato d'aria

Il calcestruzzo impregnato d'aria contiene miliardi di microscopiche cellule d'aria per piede cubo. Queste sacche d'aria alleviano la pressione interna del calcestruzzo fornendo minuscole camere in cui l'acqua si espande quando si congela.

Il calcestruzzo a circolazione d'aria viene prodotto utilizzando cemento portland a circolazione d'aria o introducendo agenti a circolazione d'aria, sotto un'attenta supervisione tecnica, mentre il calcestruzzo viene mescolato sul posto. La quantità di aria trascinata è di solito tra quattro e sette perce...

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