Decomposition of Concrete Depends on:
- Porosity of concrete
- Concentration of the acid
- Solubility of the Acid Calcium Salt
- Fluid Transport through the concrete, its temperature and pressure
Following are some remedial measures to increase the resistance of concrete or prevent it from acid attack:
- Calcium silicates can be used to fill the pores and decrease the permeability. This can be done by treating calcium hydroxide with diluted sodium silicate (also known as Water-Glass)
- Pores can also be filled by treating Calcium Hydroxide with Magnesium Fluosilicate followed by the formation of Colloidal Silicofluoric Gel to withstand acid attack
- Allowing the concrete to dry before exposure causes the formation of a calcium carbonate film produced by the action of CO2 on lime. This film blocks the pores and reduces the permeability of the surface layer. Thus a precast concrete is appreciated.
- The above method is not a permanent solution. For more protection the concrete is subjected in vacuum to silicon tetra fluoride gas which reacts with the lime as follow.
2Ca (OH)2 + SiF4 ------> 2CaF2 + Si (OH)4
This treatment can only be applied to precast concrete, which is then known as Ocrat-Concrete.
- Coal-Tar Pitch
- Bituminous Paints
- Epoxy Resins
Degradation of Concrete