The factors affecting the properties of nano-modified concrete in in seawater.
Sea water can have chlorine and sulfate ion diffusion in the concrete. However that will also depend on the pore refinement which has taken place in the concrete due to type of blending material used. In case of silica fumes the pore refinement is highly improved and therefore concrete is quite dense and highly impermeable. There are different views on use of fly ash and silica fumes. While use of fly ash consume some of hydroxide ions reducing the alkalinity in the concrete and thus making it prone to corrosion of reinforcement, on the other hand, pore refinement will reduce the permeability and concrete will be dense and will resist ingress of hostile ions for corrosion . This type of behavior is not happening with silica fumes.
- sulphate and chloride ions influence considerable impact and responsible for damage to concrete. The corrosive action of chlorides i.e. formation of chloroaluminate hydrates responsible for softening of concrete. Chemical reactions of sulphate ions by certain constituents of concrete causes expansion of concrete.
- water cement ratio, type of aggregate and cement,Depth of Cover to the Reinforcement.
- Immersion period, Diffusion of salts under water pressure, air entrainment
- Freezing and Thawing Cycle
Yes, sulphate and chloride ions influence considerable impact and responsible for damage to concrete. The corrosive action of chlorides i.e. formation of chloroaluminate hydrates responsible for softening of concrete.
Dear Prof. El-Awny,
As I understand your question, there are two facets to it, (1) what are the effects of seawater on concrete, and (2) how do these change when nanoparticles are added to concrete.
The importance of sulfate and chloride ions have already been mentioned. I would add that one very important effect of chloride ions is to contribute to the corrosion of the reinforcing steel. In terms of the number of structures affected, this is one of the most important mechanisms of concrete weathering in the world.
If the concrete is exposed only to standing water, then its diffisivity will be essential to affecting the durability to chlorides and sulfates, as it will determine the rate of their infiltration. If the concrete is exposed to wetting and drying cycles (e.g., in the spray or splash zone), then diffusivity and permeability will both be important. The diffusivity and permeability are both affected by the total porosity, pore size, and pore connectivity, which can be measured using a variety of methods (SEM, MIP, BET, etc.).
Nanoparticles have a set of complicated effects on these durability parameters. I mentioned a similar matter on a different question, and I hope it is okay I will also here attach my paper that speaks to this phenomenon extensively.
Does this help?
Dear Dr. Yonathan, thank you once for your interest.
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