Reinforced Concrete
Reinforced concrete is a composite material in which concrete's relatively low tensile strength and ductility are compensated by the inclusion of reinforcement having higher tensile strength and/or ductility, creating a versatile structural material that combines the best properties of both components.
Composition
A composite of Portland cement concrete and steel reinforcement (typically deformed steel bars, welded wire mesh, or fibers). The concrete provides compressive strength and protects the reinforcement from corrosion, while the steel provides tensile strength and ductility. The two materials work together through bond forces that develop between them.
Properties
Compressive Strength
3,000-10,000+ psi
Derived primarily from the concrete, with typical structural applications using 4,000-6,000 psi concrete.
Tensile Strength
Variable
Significantly enhanced by steel reinforcement, which carries tensile forces after concrete cracks.
Flexural Strength
Highly engineered
Designed based on reinforcement amount and placement, with steel positioned to resist tension in critical zones.
Density
145-150 lbs/ft³
Slightly higher than plain concrete due to steel reinforcement.
Fire Resistance
1-4 hours
Varies based on member dimensions, concrete cover over reinforcement, and aggregate type.
Durability
50-100+ years
Highly durable when properly designed, though vulnerable to reinforcement corrosion in aggressive environments.
Applications
Foundations
Used for footings, foundation walls, and mat foundations to distribute building loads to the soil, with reinforcement providing resistance to soil pressures and settlement stresses.
Structural Frames
Forms beams, columns, and connections in building frames, with reinforcement arranged to handle complex stress patterns and provide ductility.
Floor and Roof Systems
Creates one-way and two-way slabs, waffle slabs, flat plates, and other systems that support vertical loads and transfer them to beams and columns.
Walls
Used for bearing walls, shear walls (for lateral force resistance), retaining walls, and basement walls, with reinforcement patterns specific to each application.
Infrastructure
Essential for bridges, tunnels, dams, water tanks, and other civil infrastructure requiring durability and strength under demanding conditions.
Special Structures
Used in high-rise buildings, stadiums, shells, and other complex structures requiring engineered solutions for unique loading conditions.
Advantages
- Combines concrete's compressive strength with steel's tensile strength
- Highly versatile and adaptable to various structural forms
- Excellent durability and long service life with proper design
- Good fire resistance compared to unprotected steel
- Can be cast in place or precast for different applications
- Provides thermal mass for energy efficiency
- Relatively economical for many applications
- Resistant to weathering, abrasion, and many environmental conditions
Limitations
- Relatively high environmental impact due to cement and steel production
- Vulnerable to reinforcement corrosion, particularly in chloride-rich environments
- Prone to cracking from shrinkage, temperature effects, and loading
- Heavy weight increases foundation requirements and seismic forces
- Labor-intensive construction process requiring skilled workers
- Quality highly dependent on proper mixing, placement, and curing
- Difficult to modify or adapt after construction
- Poor thermal insulation properties requiring additional materials for energy efficiency
Sustainability Profile
Low to moderate sustainability profile, though improving with innovations. The environmental impact comes from both concrete (cement production) and steel (energy-intensive manufacturing), making reinforced concrete responsible for significant global CO₂ emissions. Sustainability improvements include: (1) Supplementary cementitious materials and alternative cements to reduce the carbon footprint; (2) High-strength concrete and steel allowing material reduction; (3) Corrosion-resistant reinforcement for longer service life; (4) Recycled content in both concrete and reinforcement; (5) Design optimization to minimize material use; (6) Emerging technologies like carbon sequestration in concrete. The material's durability and long service life partially offset initial environmental impacts when considered over the full lifecycle.