Offshore sand for reinforced concrete

A figure of 0.075% by weight of sand was arrived at as a safe limit for allowable Cl^? ion content in offshore sand for OPC based reinforced concrete. A 2 m high sand column was fabricated for checking the effects of natural drainage and simulated rain on the chloride levels in offshore sand, and the action of even 80 mm of rain was found to reduce Cl^? contents to below acceptable levels. The accelerated corrosion performance of grade 20 concrete (i.e. the most critical structural grade) with the allowable Cl^? content in the sand was satisfactory and similar to a chloride free control mix; on the other hand, a mix with seawater saturated sand (0.3% Cl^?) showed clear evidence of high corrosion.