Vibration of self consolidating concrete Casual sex dating ottawa
Typical crack pattern associated to the alkali-silica reaction affecting a concrete step barrier on a US motorway (photograph, courtesy of the Federal Highway Administration, US Department of Transportation).
Various types of aggregate undergo chemical reactions in concrete, leading to damaging expansive phenomena.
Dissolved ions, such as calcium (Ca), are leached out and transported in solution some distance.
If the physico-chemical conditions prevailing in the seeping water evolve with distance along the water path and water becomes supersaturated with respect to certain minerals, they can further precipitate, making calthemite deposits (predominately calcium carbonate) inside the cracks, or at the concrete outer surface.
The effects are more pronounced above the tidal zone than where the concrete is permanently submerged.
the expulsion of small cones (up to 3 cm (1 in) about in diameter) in correspondence of aggregate particles.
When some aggregates containing dolomite are used, a dedolomitization reaction occurs where the magnesium carbonate compound reacts with hydroxyl ions and yields magnesium hydroxide and a carbonate ion.
Carbon dioxide from air can react with the calcium hydroxide in concrete to form calcium carbonate.
This process is called carbonatation, which is essentially the reversal of the chemical process of calcination of lime taking place in a cement kiln.
For the latter reason, carbonatation is an unwanted process in concrete chemistry.