IRC 40:2002 is the Indian Standard (IRC) for standard specifications and code of practice for road bridges — cement mortar and concrete. This standard is crucial for bridge engineers involved in the design and construction of road bridges using cementitious materials. It details requirements for the quality and performance of cement mortar and concrete, including their constituent materials, mix design procedures, and construction practices. Adherence to this code ensures that concrete and mortar used in bridges meet specified strength, durability, and workability criteria, ultimately contributing to the long-term safety and serviceability of the structure. It outlines testing methods for fresh and hardened concrete, repair techniques, and considerations for aggressive environments.
This IRC code provides comprehensive specifications and codes of practice for the use of cement mortar and concrete in road bridges. It covers aspects from material selection and testing to mixing, placing, curing, and quality control, ensuring the durability and structural integrity of bridge components.
Key limits for concrete materials, durability, workability, formwork stripping times, and compressive strength acceptance criteria for road bridges.
| Reference | Value | Clause |
|---|---|---|
| Min. Grade (RCC) — Moderate Exposure— For reinforced concrete. | M25 | Cl. 5.4.2 (Table 3) |
| Min. Grade (RCC) — Severe Exposure— For reinforced concrete. | M30 | Cl. 5.4.2 (Table 3) |
| Max. Water-Cement Ratio — Moderate | 0.45 | Cl. 5.4.2 (Table 3) |
| Max. Water-Cement Ratio — Severe | 0.45 | Cl. 5.4.2 (Table 3) |
| Max. Water-Cement Ratio — Very Severe | 0.40 | Cl. 5.4.2 (Table 3) |
| Min. Cement Content — Moderate— For 20 mm nominal size aggregate. | 310 kg/m³ | Cl. 5.4.2 (Table 3) |
| Min. Cement Content — Severe— For 20 mm nominal size aggregate. | 330 kg/m³ | Cl. 5.4.2 (Table 3) |
| Min. Cement Content — Very Severe— For 20 mm nominal size aggregate. | 370 kg/m³ | Cl. 5.4.2 (Table 3) |
| Min. Clear Cover — Moderate Exposure | 40 mm | Cl. 5.4.4 (Table 5) |
| Min. Clear Cover — Severe Exposure | 50 mm | Cl. 5.4.4 (Table 5) |
| Min. Clear Cover — Very Severe Exposure | 75 mm | Cl. 5.4.4 (Table 5) |
| Max. Total Chloride Content (RCC)— For reinforced concrete from all sources. | 0.30 kg/m³ | Cl. 5.4.3 (Table 4) |
| Max. Total Acid Soluble Chloride (PCC)— For plain concrete from all sources. | 0.50 kg/m³ | Cl. 5.4.3 (Table 4) |
| Max. Chloride in Water (for RCC)— As Cl. | 500 mg/l | Cl. 4.3.2 (Table 2) |
| Max. Sulphate in Water— As SO₄. | 400 mg/l | Cl. 4.3.2 (Table 2) |
| Min. pH of Water for Concrete | 6.0 | Cl. 4.3.1 |
| Slump for Normal RCC Work— For normal vibration. | 50–75 mm | Cl. 6.2 (Table 6) |
| Slump for Pumpable Concrete | 75–100 mm | Cl. 6.2 (Table 6) |
| Max. Concrete Temperature at Placing | 40 °C | Cl. 8.4 |
| Formwork Stripping — Vertical Faces | 12–24 hours | Cl. 10.2 (Table 10) |
| Formwork Stripping — Slab Soffits— Props to be refixed until 14 days. | 7 days | Cl. 10.2 (Table 10) |
| Formwork Stripping — Beam Soffits— Props to be refixed until 21 days. | 14 days | Cl. 10.2 (Table 10) |
| Compressive Strength Acceptance (Individual)— fck is characteristic compressive strength. | ≥ (fck - 3) MPa | Cl. 11.3.1 |
| Compressive Strength Acceptance (Mean of 4)— Mean of any 4 consecutive non-overlapping samples. | ≥ (fck + 3) MPa | Cl. 11.3.1 |
IRC 40 specifies standard specifications and code of practice for road bridges — Section IX: Cement Mortar — the bridge-specific cement mortar code for masonry, plastering, pointing, and joint filling on bridge structures. While general cement mortar practices apply, IRC 40 specifies tighter requirements for the bridge environment (durability, exposure, traffic vibration).
Use IRC 40 when designing or specifying: - Cement mortar for bridge masonry (stone abutments, parapets, wing walls) - Bridge plastering (cement plaster on bridge structures) - Pointing of stone / brick masonry on bridges - Joint filling between precast components - Repair mortars for existing bridge structures
IRC bridge codes use a Section system; IRC 40 is Section IX (cement mortar). Other Sections cover specific structural / construction elements: - Section I: General features (IRC:5) - Section II: Loads + load combinations (IRC:6) - Section III: Cement concrete (plain + reinforced) (IRC:21) - Section IV: Brick + stone masonry - Section V: Steel road bridges (IRC:24) - Section VI: Composite construction (IRC:22) - Section VII: Foundations + substructures (IRC:78) - Section VIII: Bearings (IRC:83 Part II) - Section IX: Cement Mortar (this code, IRC:40)
Cement mortar in bridges differs from buildings: - More demanding exposure (rain, vibration, heavy traffic) - Stricter durability requirements (longer service life, ≥ 100 year typical) - Specific mix requirements (1:3 cement-sand for structural; 1:4 for plaster) - More rigorous quality control
Cement mortar mixes (per IRC 40):
| Application | Mix (cement:sand) | 28-day compressive strength (MPa) | |---|---|---| | Stone / brick masonry (bridge piers, abutments, parapets) | 1:3 | ≥ 8 | | High-strength masonry (heavy load) | 1:2 | ≥ 12 | | Plaster (external) | 1:4 | ≥ 5 | | Plaster (internal) | 1:5 | ≥ 4 | | Pointing | 1:3 | ≥ 8 | | Joint filling (between precast) | non-shrink grout per spec | per design |
Materials: - Cement: OPC 43 (IS 8112:1989) or higher; PPC (IS 1489 Part 1:2015) acceptable - Sand: clean river sand or manufactured sand per IS 383:2016 - Zone II preferred - Fines (passing 75 µm) ≤ 5 % (uncrushed); ≤ 15 % (M-sand) - Free of organic matter, salts - Water: per IS 456:2000 Clause 5.4 (clean, no chlorides / sulphates) - Admixtures: water-reducer per IS 9103:1999 for thick / pumped mortar
Mixing: - Mix on platform; not on ground (avoids contamination) - Dry-mix cement + sand thoroughly - Add water gradually to achieve workability - Use within 30-60 minutes of mixing (longer = set begins, weaker mortar)
Application: - Pre-soak masonry units (brick, stone) before laying - Joint thickness: 10 mm typical; 6-15 mm acceptable - Cure 7-14 days minimum (water curing essential)
Acceptance tests: - 50 mm cubes per mortar batch (per IS 4031 Part 6 / Part 7) - 7-day + 28-day compressive strength - Mortar workability (slump or vee-bee per IS 1199 Part 1:2018) - Visual inspection of completed masonry / plaster
Cube test cadence: - Per major pour / day's work - Source qualification: 6-9 cubes (3 per age × 3 ages) - Routine: 6 cubes per 50-100 m² mortar - Investigation: as needed when failure suspected
1. Wrong mix proportion. Building 1:6 used on bridge instead of 1:3; mortar weak; cracks under traffic vibration. Use IRC 40 mixes for bridge work. 2. Old / damp cement. Reactivity drops; mortar weak. FIFO + dry storage. 3. Sand with high silt / clay. Cement requirement increases; weak mortar; efflorescence. Wash sand or reject. 4. Mortar mixed too long ago. Beyond 30-60 min; set begins; weak. Use immediately after mixing. 5. Inadequate curing. Mortar dries quickly in bridge structures (exposed); no curing = weak. Water curing 7-14 days mandatory. 6. Joint thickness inconsistent. Variable joints; aesthetic + structural inconsistency. Use mortar gauge. 7. No cube tests for routine mortar work. Cannot verify quality; failure investigation impossible. Cubes per pour. 8. Water with chlorides / sulphates. Aggressive to mortar + reinforcement. Test water source. 9. Plastering on dry / dusty masonry. Plaster doesn't bond; falls off. Wet + clean substrate. 10. No expansion joint at long stretches. Mortar cracks at thermal movement. Provide expansion joints per design. 11. Cold weather mortar without precautions. Slow set; freezing; weak mortar. Use accelerator + protect from cold. 12. No pointing of stone masonry. Mortar exposed to rain; erosion + weakening. Pointing essential.
Bridge structure construction cascade:
1. Foundation (IRC:78:2014) — concrete piles / shallow per design. 2. Substructure — abutments, piers, wing walls (concrete + masonry mortar per IRC 40). 3. Bearings (IRC:83 Part II) — elastomeric / steel / pot bearings. 4. Superstructure (IRC:21, IRC:22, IRC:24, IRC:112) — concrete / steel / composite. 5. Approach embankments (IRC:36:2010) — earthwork per IRC 36. 6. Wearing surface + drainage. 7. Parapets + railings (IRC:99:2018) — masonry / steel barriers. 8. Mortar work throughout (per this code, IRC 40) — masonry, plaster, pointing, joint filling. 9. Quality control — mortar cube tests, masonry inspection, finish quality. 10. Bridge inspection (IRC SP 85:2019) — periodic in service.
IRC 40 is one of the workhorse bridge codes — small but essential. Every bridge has masonry / plaster / pointing work; IRC 40 ensures it's done to bridge-grade quality + durability.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Concrete Grades | |||
| Water-Cement Ratio (Max for Severe Exposure) | |||
| Cement Content (Min for Severe Exposure) | |||
| Curing Duration |