Basic piling methods - Piling Engineering - page 94

Table 3.12 Miscellaneous aggressive agencies that may cause attack of concrete

Agent Attack

Inorganic acids (e.g. sulphuric, nitric, Can dissolve components of concrete;

severity depends on concentration. hydrochloric acid)

Organic acids (e.g. acetic, lactic, formic, Can slowly dissolve concrete. The attack is

generally slow. humic acid)

Alkalis (e.g. sodium and potassium hydroxide) Alkalis such as these will dissolve concrete

when highly concentrated.

Plant and animal fats (e.g. olive oil, fish oil, Bond strength may be reduced.

linseed oil)

Mineral oils and coal tar distillates (e.g. light and
heavy oils, paraffin)

If of low viscosity, these agents can degrade
concrete. Phenols and creosols corrode.

Organic matter (e.g. landfill refuse) Organic matter can degrade concrete if

hydrolysis results in lime removal.

3.7.2.4 Miscellaneous agencies aggressive to concrete

Nixon et al ., (2003) lists various miscellaneous aggressive agencies that may cause
attack of concrete (Table 3.12).

3.7.3 Protection of concrete piles

Although the provision of dense and impermeable concrete reduces the attack of
concrete by aggressive agencies, other means that can be considered include the use
of coatings on pre-cast piles but ultimately, for cast-in-place piles in highly aggressive
ground, a permanent casing may provide the best alternative. The permanent casing
or sleeve may be flexible or rigid (usually uPVC). The sleeve may be placed inside
the temporary casing, which has been advanced into the ground and may be fixed to
the reinforcing cage. Alternatively, a flexible sleeve may be attached to the outside of
the temporary casing, and remains behind when the casing is withdrawn. In granular
soils, it is possible for the sleeve to tear, and a test drive of the system should be carried
out. A more certain measure, despite the cost, is to employ permanent stainless steel
casing for the upper part of a pile.