IRC Code: Guidelines for the Use of High Performance Concrete (Including Self Compacting Concrete) in Bridges (IRC:SP:70-2005)

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High-Performance Concrete (HPC) is revolutionizing bridge construction by offering enhanced durability, strength, and workability. The IRC:SP:70-2005 provides comprehensive guidelines on the selection, design, and application of HPC in bridges. These guidelines ensure high structural integrity, longevity, and reduced maintenance costs, making them essential for engineers and infrastructure developers.

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Scope of IRC:SP:70-2005

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The scope of the IRC:SP:70-2005 includes the application of HPC in both the superstructure and substructure of bridges. The document covers material selection, mix design, permissible stresses, and quality control measures. The guidelines emphasize the use of international standards, such as BS:5400, EURO codes, and AASHTO specifications, to enhance the quality and reliability of HPC in bridge projects.

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Key Terminologies in High Performance Concrete

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1. High Performance Concrete (HPC)

HPC refers to concrete that provides high strength, durability, low permeability, and enhanced workability beyond conventional concrete. It is achieved through optimized mix designs and strict quality control measures.

2. Self-Compacting Concrete (SCC)

SCC is a subset of HPC that flows under its own weight without requiring mechanical vibration, ensuring homogeneous placement and reduced labor efforts.

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Materials Used in High Performance Concrete

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1. Cement Types

Approved cement types for HPC include Ordinary Portland Cement (43 and 53 grades), Rapid Hardening Cement, Sulfate Resistant Cement, and Portland Pozzolana Cement. The selection depends on the specific requirements of durability and strength.

2. Mineral Admixtures

HPC incorporates fly ash, granulated slag, and silica fume to improve performance. The proportions must adhere to the following limits:

• Fly Ash: 20%-35% by mass of cement
• Granulated Slag: 50%-70% by mass of cement
• Silica Fume: As per IS:15388 standards

3. Chemical Admixtures

The use of superplasticizers and high-range water reducers helps improve the workability of HPC while maintaining a low water-cement ratio for high strength and durability.

4. Aggregates

Both coarse and fine aggregates must conform to IS:383 standards. The maximum aggregate size should not exceed 20mm to ensure ease of placement and uniform distribution.

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Concrete Mix Design and Strength Criteria

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Strength Grades of HPC

HPC is categorized into different grades based on characteristic compressive strength at 28 days:

• M40 to M80 (where M40 indicates 40 MPa strength, M80 indicates 80 MPa strength)

Water-Cement Ratio & Cement Content

• The maximum water-cementitious material ratio should be 0.40.
• The minimum cement content should be 380 kg/m³, and the maximum should not exceed 450 kg/m³.

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Durability and Quality Control Measures

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1. Impermeability and Crack Resistance

HPC should be designed to resist:

• Chloride penetration (RCPT test < 800 coulombs)
• Water permeability (as per DIN 1048 standards)
• Shrinkage and cracking by using appropriate curing methods

2. Curing Requirements

Due to its low bleeding characteristics, HPC requires immediate and adequate curing. A combination of moist curing, plastic sheets, and curing compounds is recommended for at least 14 days to prevent shrinkage cracks.

3. Quality Assurance

Strict batching, mixing, and testing protocols must be followed, with adherence to IRC:SP-47 quality assurance guidelines. Proper trials should be conducted to assess workability, strength, and durability before field implementation.

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Acceptance Criteria for High Performance Concrete

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Concrete must pass the following tests before acceptance:

1. Compressive Strength Test – Should meet the specified characteristic strength (M40-M80)
2. Rapid Chloride Permeability Test (ASTM C-1202/AASHTO T-277) – Chloride permeability should be less than 800 coulombs
3. Water Permeability & Absorption Tests – As per DIN:1048 and BS:1881 standards

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Conclusion

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The IRC:SP:70-2005 plays a crucial role in guiding engineers on the correct usage of High-Performance Concrete and Self-Compacting Concrete in bridges. Following these guidelines ensures enhanced strength, durability, and long-term performance, making it a vital reference for modern bridge construction in India.

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