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Concrete in Corrosive environment

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Deterioration of concrete has been a very big problem in Saudi Arabia. Concrete structures built in 70's and 80's deteriorated within 10 years ! The environment here is very aggressive, high sulfate and chloride content in soils.

I have not come across hydrogen sulfide and methane. Harold Sprague has already posted on this.

For chlorides and sulfates, the practice here is :

1)Water cement ratio of 0.4 although lately research performed at KFUPM Dhahran(University of Petroleum and Minerals) recommends 0.35.
2) A rich concrete mix. Minimum cement content 350 kg/cu meter. Maximum 370.
3) Maximum TDS (AASHTO T 26) in water 500 PPM.
4) FBE Epoxy coated reinforcement.
5) Restriction on Agrregates beyound ASTM C33
6) Increase in concrete cover. The minimum cover used is 3 ins (75mm) and as high as 4 ins (100mm) for foundations and piers up to the base plate. This may be used for your pile caps even if formed.
7) External Coatings, coal tar or Bitumen. (Pile caps)
8) Of course curing. Curing practices and type of water used here in the past have been very bad and there seems to be a lack of understanding that curing is essential for durable concrete.
9)Restictions in percentage of chlorides in concrete. 
10) Type of cement

Latetely, microsilica or pozzalans have been used. Be careful on curing.

For the grade slabs, Galvanized reinforced bars or mesh ASTM A 767 may be considered. This is an alternate to FPE coated Bars (ASTM A775)

Also recommend that you review ACI 201 (Guide to Durable Concrete) and ACI 222 (Corrosion of metals in Concrete).

Corrosion engineers have come up with some fancy systems which need to be maintained. I have never used them but I understand it is costly.

Eqbal Kassam