concrete cover

Md. Ashraful Haque, 15-Feb-2005
ভিউ : 64714

	Environ-ment	Exposure Conditions	Minimum N/mm2
			20	25	30	35	40	45	50
	Mild	Concrete surfaces protected against weather or aggressive conditions	30	25	20	20	20**	20**	20**
Nom- inal cover (mm)	Mode- rate	Concrete surface away from severe rain Concrete subject to condensation Concrete surfaces continuously under water Concrete in contact with nonaggre-ssive soil	40	35	30	25	20	20	20
	Severe	Concrete surfaces exposed to severe rain, alternate wetting and drying or severe condensation		45	40	30	25	25	20
	Very severe	Concrete surfaces exposed to sea water spray, corrosive fumes			50	40	30	30	25
	Extreme	Concrete surfaces exposed to abrasive action, e.g. sea water carrying solids or flowing water with pH ≤ 4.5 or machinery or vehicles				60	50	40	30
Maximum water/cement ratio			0.65	0.65	0.60	0.55	0.50	0.45	0.42
Minimum cement content, (kg/m3)			315	325	350	375	400	410	420
* This table relates to aggregate of 20 mm nominal maximum size. ** May be reduced to 15 mm provided the nominal maximum aggregate size does not exceed 15 mm.