IRC 28:1967 is the Indian Standard (IRC) for tentative specifications for the construction of cement concrete roads (over a water-bound macadam sub-base). IRC 28:1967 specifies construction of cement concrete (rigid) pavements over water-bound macadam sub-base — primarily for rural roads, village connections, and minor district roads. While superseded in spirit by the more comprehensive IRC 58 (rigid pavement design) and IRC SP 62 (low-volume concrete roads), IRC 28 remains referenced for specific rural application construction methodology. Key parameters: WBM sub-base 150-200 mm, prime-coated; concrete M25-M30 grade with w/c < 0.50; slab thickness 150-250 mm (200 mm typical for PMGSY rural); transverse contraction joints at 4-5 m with dowel bars; longitudinal joints with tie bars; water curing minimum 14 days. Concrete roads are 1.5-2× initial cost of flexible but 2-3× longer life (20-30 years vs 10-15 years for flexible). For PMGSY rural roads, concrete is often preferred due to reduced maintenance burden — rural maintenance capacity is limited. Amendment No. 1 (2010) aligned with IS 456/IRC 44 updates on concrete mix design. IRC 28 compliance + IRC 58 design + IRC SP 62 for low-volume choice gives comprehensive rigid pavement guidance for rural India.
Specifies construction methodology for cement concrete (rigid) pavements over water-bound macadam sub-base — addressing sub-base preparation, concrete mix, placement, finishing, and curing for rural and low-traffic concrete road projects.
Key values for concrete mix, jointing, construction tolerances, and material specifications for cement concrete roads.
| Reference | Value | Clause |
|---|---|---|
| Min. Concrete Strength (28-day)— Minimum works cube crushing strength. Approx. 27.5 MPa. | 280 kg/cm² | Cl. 5.1 |
| Min. Cement Content— For concrete used in the pavement slab. | 330 kg/m³ | Cl. 5.2.1 |
| Max. Water-Cement Ratio— By weight. To be reduced if higher strength is needed. | 0.55 | Cl. 5.2.2 |
| Workability (Slump)— For hand-operated vibratory screeds. Max. 12 mm for mechanical finishers. | 25 mm | Cl. 5.2.3 |
| Max. Coarse Aggregate Size— Typically 40 mm nominal size is used. | ≤ 1/4 of slab thickness | Cl. 3.3.1 |
| Coarse Agg. Grading (40mm)— Percent passing 20 mm IS Sieve for 40 mm nominal size aggregate. | 30-70% | Cl. 3.3.2 (Table 2) |
| Fine Agg. Grading (Zone II)— Percent passing 600-micron IS Sieve for Grading Zone II sand. | 15-34% | Cl. 3.2.2 (Table 1) |
| WBM Sub-base Thickness Tolerance— Tolerance for the finished surface of the water-bound macadam sub-base. | ± 12 mm | Cl. 4.2 |
| Formwork Alignment Tolerance— Maximum allowable variation from the true line. | 3 mm | Cl. 6.1 |
| Slab Thickness Deficiency (Core)— Deficiency of any individual core shall not be more than 6 mm from specified thickness. | ≤ 6 mm | Cl. 6.5.2 |
| Surface Regularity— Maximum permissible irregularity under a 3-metre straight-edge. | ≤ 4 mm | Cl. 11.1 |
| Max. Expansion Joint Spacing— For slabs laid in cold weather. Reduced to 18-22.5 m for hot weather. | 27 m | Cl. 8.2.1 |
| Expansion Joint Width | 20 - 25 mm | Cl. 8.2.1 |
| Max. Contraction Joint Spacing— For unreinforced slabs. | 4.5 m | Cl. 8.3.1 |
| Contraction Joint Groove Depth | 1/4 to 1/3 of slab depth | Cl. 8.3.1 |
| Dowel Bar Diameter (20cm Slab)— For a typical 20 cm thick slab. | 25 mm | Cl. 8.2.2 (Table 3) |
| Dowel Bar Spacing (20cm Slab)— For a typical 20 cm thick slab. | 30 cm c/c | Cl. 8.2.2 (Table 3) |
| Tie Bar Diameter (Longitudinal Joint) | 12 mm | Cl. 8.4.2 |
| Tie Bar Spacing (Longitudinal Joint) | 60 cm c/c | Cl. 8.4.2 |
| Min. Curing Period— Concrete to be kept continuously moist. | 14 days | Cl. 10.1 |
| Strength Test Acceptance (Individual)— Strength of any individual cube shall not be less than 80% of specified works strength. | ≥ 80% of specified strength | Cl. 12.2 |
IRC 28 (1967) provides Tentative Specifications for the Construction of Cement Concrete Roads (Over a Water-Bound Macadam Sub-base) — the IRC's older specification for cement-concrete pavement built over a WBM sub-base. While modern projects largely use DLC (Dry Lean Concrete) or stabilised sub-base per IRC:58:2015 + IRC:SP-89:2018, IRC 28 remains valid + applied on rural roads + lower-class roads.
Use IRC 28 when you are: - Constructing cement-concrete pavement on traditional WBM sub-base - Doing rural / district CC pavement with local materials - Specifying economy CC pavement where DLC is uneconomic - Restoring older CC roads built over WBM - Doing PMGSY rural CC with traditional WBM sub-base
What IRC 28 covers: - WBM sub-base preparation - Concrete pavement layer specifications - Joint design + sealants - Construction procedure - Quality control - Long-term performance
WBM sub-base context: Water-Bound Macadam (WBM) is a granular sub-base where compacted aggregate is washed into place with water + screening. It's the predecessor of DLC + modern stabilised bases.
WBM specifications (per IRC 19/20/21 series): - Aggregate: 50-90 mm primary stone + 25 mm closing stone - Compacted layer thickness: 75-100 mm per layer - Multiple layers possible: typical 200-300 mm total - Wash + roll method or modified manual placement - CBR target: 30-50 % at top of layer
Pavement design: - Pavement thickness: 150-250 mm (typical for rural NH/SH) - Concrete grade: M30-M35 (older spec; modern projects use M40+) - Slab dimensions: 4-6 m × lane width (typically 3.5-4 m) - Joints: transverse contraction + longitudinal + construction - Reinforcement (optional): edge bars at joints; mesh in transition zones
Sub-base preparation: - WBM laid + compacted to design level - Top surface free of dust + loose material - Wet sub-base before concrete (slightly damp surface)
Concrete placement: - Mix: standard or paving mix per IRC:15:2017 (modern reference) - Slump: 25-75 mm (slipform paver) or 50-75 mm (hand-spread) - Vibration: thorough; deeper vibration not needed for thin slabs - Finishing: floor + edge with appropriate tools - Surface texture: brushed or tined for skid resistance
Curing: - Mandatory 7+ day water curing - Curing compound acceptable for short-term - Polyethylene sheets for dry climate - Critical first 24 hours
Joint design + sealants: - Transverse contraction joints: 4-6 m spacing - Longitudinal joints: lane centre, every 4 m - Sawing: within 6-12 hours of placement - Depth: 1/3 of slab thickness - Width: 3-5 mm initial, sealed with bituminous or polymer compound - Sealants: silicone or polysulphide per IS 11512 (modern); bituminous for older spec
Quality control: - Cube samples: 1 per 50-100 m³ - Beam tests: flexural strength per 200 m³ - Cover meter: ensure adequate reinforcement cover - Surface evenness: 3 mm under 3-m straight-edge - Joint sawing timing: 6-12 hours from placement
Acceptance: - 28-day cube strength meets design (M30 minimum for rural; M40+ preferred) - Flexural strength (beam test) meets design - Surface evenness within tolerance - Joint sealant integrity - No visible distress at handover
Pavement thickness (IRC 28 framework): - Light traffic (< 1,000 commercial vehicles/day): 150-180 mm - Moderate traffic (1,000-3,000): 180-220 mm - Heavy traffic (3,000-6,000): 220-250 mm - For heavier traffic, modern projects use DLC sub-base + thicker slab
WBM sub-base details: - Primary aggregate: 53 mm down to 22.4 mm - Closing aggregate (screening): 11.2 mm down to dust - Compacted thickness: 75 mm + 75 mm = 150 mm total OR 100 mm single layer - CBR after compaction: ≥ 30 % - Density: ≥ 95 % of MDD
Concrete mix (IRC 28 minimum spec): - Cement content: 350-400 kg/m³ - W/C ratio: 0.40-0.50 - Slump: 25-75 mm - Aggregate: crushed angular, max size 25 mm - Air entrainment: 3-5 % - Compressive strength (28-day cube): ≥ 30 MPa (M30 minimum) - Flexural strength (beam): ≥ 4 MPa
Joint depth + width: - Transverse contraction joint depth: 1/3 × slab thickness (e.g., 50-65 mm for 150-200 mm slab) - Width at saw: 3-5 mm initial - Sealant gap: typically 6-13 mm wide × 13-25 mm deep (after re-sawing)
Construction tolerances: - Slab thickness: ± 10 mm of design - Slab level: ± 10 mm of design - Surface evenness: 3 mm under 3-m straight-edge - Cross-fall: ± 0.5 % of design
Curing: - Initial: water spray or wet burlap within 30 min - Continuous: 7+ days, 14+ days for premium roads - Curing compound: 4-6 m²/L white-pigmented - Polyethylene sheets cover acceptable
Maintenance schedule: - Annual visual inspection - Joint resealing every 5-10 years (sealant degrades) - Surface dressing or grinding at year 8-12 (skid restoration) - Major rehabilitation at year 20-25 (slab replacement / overlay) - Service life: 25-30 years on average
Modern alternative (preferred for new projects): - DLC sub-base (better support) per IRC:58:2015 - Higher concrete grade (M40+) - Continuously reinforced (CRCP) per IRC:SP-71:2018 for premium projects
1. WBM sub-base inadequate. Compaction below 95 % MDD; uneven loading on slab; cracking. Strict WBM compaction + density verification. 2. Concrete placed on dry WBM. Water absorbed from concrete; surface dehydration; cracking. Wet WBM surface before concrete placement. 3. Joint sawing delayed > 12 hours. Random cracking between joints; pattern lost. Saw at 6-12 hours from placement. 4. Curing inadequate. Surface dries within 24 hours; shrinkage cracks; strength loss. 7+ day water curing minimum. 5. Concrete grade below M30. Strength inadequate; cracking + spalling. M30 minimum; M40+ preferred for heavier traffic. 6. No joint sealing. Cracks + water entry to slab; corrosion + spalling. Mandatory sealant per IS 11512. 7. Lift thickness too high. Single 200+ mm lift; vibration inadequate; honeycombing. Multi-layer placement or thinner lifts. 8. No reinforcement at transition zones. Cracks at abutments, drainage structures, intersections. Edge / corner reinforcement. 9. Surface texture inadequate. Smooth surface; skid resistance poor. Brushed or tined finish. 10. Traffic opened too soon. Loading before cure complete; cracking. 7+ day cure for normal loads; 14+ for heavy. 11. WBM aggregate quality poor. Local aggregate substandard; CBR < 30 %; structural performance below design. Acceptance criteria per aggregate type. 12. No documentation. Construction records lacking; future maintenance + warranty uncertain. Daily logs + procedures. 13. Mix design too thin (low cement). Cost-cutting reduces cement; strength below design. Verify mix per batch. 14. No durability consideration. No air entrainment in cold regions; freeze-thaw damage. Add air entrainment where freeze-thaw concern. 15. Surface dressing on cement-concrete. Inappropriate; surface dressing doesn't bond to CC. Use grinding or BC overlay instead. 16. Wrong reference code. IRC 28 used for premium project where modern IRC:58 + IRC:SP-71 are more appropriate. Modern projects should use current IRC.
Cement-concrete road project (IRC 28 framework) — touchpoints:
1. DPR / pavement design: - Identify CC pavement as appropriate technology - Sub-base selection: WBM (IRC 28) vs DLC (modern, IRC 58) - Slab thickness from traffic + subgrade - Joint pattern + sealant specification - Mix design (M30-M40)
2. Site preparation: - Sub-grade compaction per IRC:36:2010 - WBM sub-base construction (primary + closing layers) - Compaction + density verification - Surface preparation for concrete pour
3. Mix design (laboratory): - Cement content + W/C ratio - Aggregate gradation + properties - Cube + beam strength validation - Workability + finishability
4. Trial section: - 50-100 m at site - Validate mix + workability + finishability - Cores for thickness + strength
5. Mass production: - Continuous concrete batching + delivery - Slipform paver (preferred) or hand-spread - Vibration + finishing - Joint sawing at 6-12 hours - Curing initiation
6. Quality control: - Cube + beam samples - Density measurement - Surface evenness check - Joint sawing depth + timing
7. Curing: - Water curing 7-14 days - Curing compound + sheets - Joint sealing after 28-day cure
8. Pre-opening: - 28-day cube strength verification - Surface inspection - Skid resistance check (if required)
9. Operations + maintenance: - Annual visual inspection - Joint resealing every 5-10 years - Service life 25-30 years on average
IRC 28 remains the practical reference for traditional CC roads using WBM sub-base — applied on PMGSY + rural district roads + smaller state highways. Modern NH 4/6-lane projects use IRC:58:2015 + DLC sub-base for higher performance.