Case 3

Navigation

Good Practices

Preventive Measure

The concrete should be designed with its purpose and surrounding environment in mind. Taking into account the material, construction method as well as quality control.

Environment	Exposure conditions
Mild	Concrete surfaces protected against weather or aggressive conditions
Moderate	Exposed concrete surfaces but sheltered from severe rain or severe traffic Concrete surfaces continuously under non-aggressive water Concrete in contact with non-aggressive soil Concrete subject to condensation
Severe	Concrete surfaces exposed to severe rain, alternate wetting, and drying or occasional freezing or severe condensation Concrete surfaces are occasionally exposed to light traffic
Very severe	Concrete surfaces are occasionally exposed to seawater spray (directly or indirectly) Concrete surfaces exposed to corrosive fumes and heavy traffic
Most severe	Concrete surfaces frequently exposed to seawater spray (directly or indirectly) and heavy traffic
Abrasive	Concrete surfaces exposed to abrasive action

Table 1: Classification of exposure conditions [3]

The type of environment affects the rate of degradation of the concrete. In areas with heavy corrosive fumes or salt exposure, there is a higher potential for corrosion. The admixture and concrete grade should be sufficiently adjusted to account for such factors

Concrete Grade	30	35	40	45	50
Minimum cement content (kg per m³)	275	300	325	350	400
Maximum cement content (kg per m³)	550	550	550	550	550
Maximum % of Fine Aggregate to Total Aggregate	50	50	50	50	50
Maximum water-to-cement ratio	0.55	0.50	0.45	0.40	0.40

Table 2: Designed mix of concrete [4]

Concrete quality should be sufficiently tested before placing this includes the measuring of water to cement ratio and slump testing. Additionally, if the concrete is placed from a distance away it should not be allowed to fall more than 1 to 1.5 meters. This can be achieved with the aid of a tremie pipe. The concrete should also be compacted to minimize the amount of void space present.

Curing concrete should be covered in high-temperature environments which may result in rapid loss of water. This should be supplemented by frequent spraying of concrete to reduce the rate of rapid water loss in a process known as moist curing.

The reinforcement bar within the concrete should also be amply protected by having sufficient nominal cover distance.