The concrete and RCC gets decayed under the following conditions.

1. Chemical attack: Due to any chemical attack because free CaO if present in Portland cement reacts with different chemical fumes on contact.

2. Acidity: In acidic environment /moisture/water with PH <7, the CaO dissolves and concrete gets weak. The deterioration is directly proportional to acidity .Higher acidity, greater rate of deterioration.

3. Sulphates and Chlorides: When water used to make concrete contains higher % of sulphates and chlorides, decay is higher, because the CaO in concrete is removed by these ions.

4. Only Sulphates: These cause very serious decay, as it affects C3A and form sulpho aluminates, causing volume expansion of concrete. This results in reduction in life of concrete.

5. Mineral oil: If concrete comes or remain in contact with mineral oil for some period, its abrasion resistance gets reduced considerably.

6. Sugar: Concrete strength gets seriously affected if sugar gets mixed with it