The effect of sea water on hardened concrete is to

Explanation:

Effect of sea water on hardened concrete:

• The constituents of seawater reacts chemically with constituents of cement concrete which results damage to the concrete structure in several ways.
• The magnesium sulfate present in seawater reacts with calcium hydroxide of cement and forms calcium sulfate as well as magnesium hydroxide precipitation.
• Magnesium sulfate also reacts with hydrated calcium aluminate and forms calcium sulpho aluminate.
• These final formations are the primary reasons for chemical attack on concrete structures.
• The deterioration of concrete structures by seawater is more due to leaching rather than expansion of concrete.
• Leaching more effects the small concrete structures than expansion while large concrete structures are effected by leaching as well as expansion.
• Sulfates attack the concrete and cause expansion but due to the presence chlorides in seawater the swelling of concrete retards.  Hence, erosion and loss of concrete takes place without showing much Expansion.
• Sea water decrease concretes strength and durability.