ENVIRONMENTAL EXPOSURE CONDITIONS OF STRUCTURES

ENVIRONMENTAL EXPOSURE CONDITIONS OF STRUCTURES

S.N.	Environment	Exposure Conditions
i	Mild	Concrete surfaces protected against weather or aggressive conditions, except those situated in coastal areas
ii	Moderate	Concrete surface sheltered from severe rain or freezing whilst wet; concrete exposed to condensation and rain, concrete continuously under water; concrete in contact or buried under non-aggressive soil/ground water; concrete surfaces sheltered from saturated salt air in coastal area
iii	Severe	Concrete surfaces exposed to severe rain, alternate wetting and drying or occasional freezing whilst wet or severe condensation; concrete completely immersed in sea water; concrete exposed to coastal environment
iv	Very Severe	Concrete surfaces exposed to sea water spray, corrosive fumes or severe freezing conditions whilst wet; concrete in contact with or buried under aggressive sub-soil/ground water
v	Extreme	Surfaces of members in tidal zone; members in direct contact with liquid/solid aggressive chemicals

Source: Table 3 of IS: 456 – 2000

Minimum cement contents, maximum water-cement ratio and minimum grade of concrete for different exposures with normal weight aggregates of 20 mm nominal maximum size

Exposure Conditions	Plain Concrete			Reinforced Concrete
	Minimum cement content kg/cum	Maximum free water-cement ratio	Minimum grade of concrete	Minimum cement content kg/cum	Maximum free water-cement ratio	Minimum grade of concrete
Mild	220	0.60	–	300	0.55	M 20
Moderate	240	0.60	M 15	300	0.50	M 25
Severe	250	0.50	M 20	320	0.45	M 30
Very Severe	260	0.45	M 20	340	0.45	M 35
Extreme	280	0.40	M 25	360	0.40	M 40

Source: Table 5 of IS: 456 – 2000