Concrete

• Concrete is strong in compression but weak in tension . 
• Its tensile strength is only about 10 % - 20 % of its compressive strength . 
• To overcome its weakness in tension , concrete tension members are either : 

- reinforced with steel bars or presstressed with steel wires or cables .

Properties of concrete 

• Strength varies according to mix proportion 
• High compressive strength 
• Very good fire protection 
• Low stiffness comparted to steel 
• Low strength to weight ratio 
• Low tensile strength , Need to be : 

Reinforced by steel bars

Prestressed by steel wires . cables 

Used for : 

- Low rise buiding frames 

- High rise building frames