Case 3
- Introduction
- Causes of Defects
- Good Practices
- Standards
- Maintenance and Diagnostics
- Remedial
- Similar Cases
- References
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 |
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 |
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.