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Aggressive Soil - Steel and Concrete

posted Jul 20, 2019, 7:54 AM by jeffery jim

There is this query coming in about the use of DI pipe instead of MSCL pipe because of aggressive ground. Nevertheless, the site have to aggressive ground except for remote case where there is a lower pH reading close to a drain, garage and recycle collection center. After dismantling these structures, the source of such aggressive substance will no longer affect the underground pipe since by default, the original ground is not filled with possible pyrite. The other possibility is possible runoff from other areas contaminated with acidic compound(s) or substance(s).

Pyrite is a byproduct from certain earth with acid sulfate composition which is mainly available around the coast line in Sabah and at times, it is reported in SI report. Nevertheless, for overall justification, the Sabah Soil Map is the best resource to have indicative and general for the soil condition.

But in case there is the brownfield area where there is possibility of extreme cases with highly aggressive ground, it is best to refer to BRE SP1 as a guideline for substructure or foundation design and as a basis to make projected calculation on corrosion based on NACE requirements.

Between concrete and steel, the concrete substructure would be worrisome when the concrete is below grade G40 which is less robust since most of these grades have higher than 0.40 free water cement ratio. This induces volatile and aggressive substance to penetrate into the concrete by aggravating the concrete cover and reach the reinforcement bar. Pitting will cause loss of surface and subsequently reduced the "As" of the designated concrete structural member(s). Hence this will reduce the capacity of the foundation.

Image result for corroded pipes