Human Factors Causing Concrete Failures

1. Faulty Design

• Improper selection or detailing of reinforcement
• Inadequate joint provision e.g. movement ( expansion or contraction ) joint .
• Under design

2. Inferior Material

• Unsuitable substitution of construction materials when specified materials are unavailable .
• Partially hydrated cement : lumpy cement
• Contaiminated aggregates : aggregates with high salt or silt content .
• Contaiminated water : polluted water used for mixing .
• Reinforcement bars with loose rust & scale , rusty prestressing strand .
• Even with good constituent materials , concrete mixed too long before use can cause difficulties in placing & compacting

3. Poor Construction Practice

• Adding too much water to improve workability : reduce strength , incrase shrinkage
• Inadequate vibration : honeycomb
• Reduce concrete cover
• Improper placing of concrete such as dropping concrete from a great height .
• Lack of curing : imcomplete hydration of cement .
• Essential practice need to be considered include :

- Site operatives are given clear instructions concerning materials & standards of workmanship .
-Adequate supplies of the correct materials are available on site when needed .
- Sufficient quality control is provided during the course of the construction .
4. Abuse of Structure

• Overloading - excessive loading beyond the elastic limit of concrete may result in creep , other common defects in concrete as a result of overloading include spalling , cracking , flexural ^ shear fractures & local distingration .
• Lack of Maintenance
• Vandalism