Correct option is C
Concrete can undergo potential degradation due to the Alkali–Silica Reaction (ASR):
Alkalies (Na₂O, K₂O) present in cement react with reactive silica in certain aggregates.
In the presence of moisture, this reaction forms an expansive alkali–silica gel.
The expansion causes cracking, loss of strength, and durability issues in concrete.
Why other options are incorrect:
Polypropylene fibres are chemically inert in concrete.
Potable water does not cause alkali-related degradation.
Naphthalene-based admixtures (plasticizers/superplasticizers) are not involved in ASR.
