Specifications for Bituminous Macadam (First Revision)

The Introduction of IRC 27 outlines the document structure and publication history but does not provide specific formulas. Key specifications related to materials include the combined aggregate grading and bitumen content as per Table 4 in Clause 3.4.2. This table specifies grading limits for two nominal maximum aggregate sizes (40 mm and 19 mm) and corresponding bitumen contents (3.3% and 3.4%). The grading must avoid gap grading by ensuring the combined aggregate grading does not vary from the lower limit on one sieve to the higher limit on the adjacent sieve. Bitumen content adjustments are allowed based on aggregate specific gravity and climatic conditions. Layer thicknesses are also specified for each grading. This forms the basis for mix design and quality control in bituminous road construction.

Sources: Clause 3.4.2, Table 4

IRC 27 defines the scope and key specifications for bituminous road construction including materials, construction, and quality control. The scope covers hot mix plants, pavers, aggregate grading, bitumen content, and testing frequencies. Key formulas and tables include:

• Acceptance criteria for density tests (N=3): Mean value ≥ specified value + [1.65 - 1.65/√N] × standard deviation (Clause 1.65).

• Aggregate Grading and Bitumen Content (Table 4, Clause 3.4.2):

• Quality Control Tests and Frequencies (Table 7, Clause 5.3): Includes tests for binder quality, aggregate properties, mix grading, stripping, water sensitivity, temperature, binder content, spread rate, and density with specified minimum frequencies.

These define the fundamental framework for materials, plant features, mix design, and quality assurance in bituminous road works per IRC 27.

Sources: Clause 1.65, Clause 3.4.2, Table 4, Clause 5.3, Table 7

Key materials specifications from IRC 27 include:

• Aggregate Grading and Bitumen Content (Clause 3.4.2, Table 4):

  Grading	1	2
  Nominal max aggregate size	40 mm	19 mm
  Layer thickness	80-100 mm	50-75 mm
  IS Sieve size (mm)	Cumulative % passing
  45	100	-
  37.5	90-100	-
  26.5	75-100	100
  19	-	90-100
  13.2	35-61	56-88
  4.75	13-22	16-36
  2.36	4-19	4-19
  0.3	2-10	2-10
  0.075	0-8	0-8
  Bitumen content	3.3%	3.4%

• Bitumen content is based on aggregate specific gravity 2.7; adjust proportionally if higher. For cold regions (max daily mean ≤30°C and min ≤-10°C), bitumen content may increase by 0.5% (Clause 3.4.2).

• Coarse Aggregate Properties (Clause 3.2.2, Table 3):

  Property	Requirement	Test Method
  Cleanliness (max passing 0.075 micron)	5%	IS:2386 Part I
  Flakiness & Elongation Index (combined)	Max 40%	IS:2386 Part I
  Los Angeles Abrasion Value	Max 40%	IS:2386 Part IV
  Aggregate Impact Value	Max 30%	IS:2386 Part IV
  Soundness (Sodium Sulphate)	Max 12% (5 cycles)	IS:2386 Part V
  Soundness (Magnesium Sulphate)	Max 18%	IS:2386 Part V
  Water Absorption	Max 2%	IS:2386 Part III
  Stripping (Bitumen coating retention)	Min 95%	IS:6241
  Water Sensitivity (Retained Tensile Strength)	Min 80%	ASHTO 283

• At least 90% of crushed gravel retained on 4.75 mm sieve must have two fractured faces (Clause 3.2.2).

• Quality Control Tests (Clause 5.3, Table 7): Frequent tests on bitumen quality, aggregate properties, mix grading, stripping, water sensitivity, temperature, binder content, spread rate, and density are mandated with specified minimum frequencies.

These ensure material quality and mix uniformity for durable bituminous pavement construction.

Sources: Clause 3.4.2, Table 4, Clause 3.2.2, Table 3, Clause 5.3, Table 7

As per IRC 27, Clause 3.1.1, the bitumen used shall be viscosity graded paving bitumen complying with IS:73, selected based on climatic conditions and traffic. Clause 3.4.2 and Table 4 specify the combined aggregate grading and bitumen content for bituminous macadam. The grading must avoid gap grading by ensuring the combined aggregate grading does not vary from the lower limit on one sieve to the higher limit on the adjacent sieve. The key specifications from Table 4 are:

*Nominal maximum aggregate size is the largest sieve size on which aggregate is retained.

**Bitumen content corresponds to aggregate specific gravity of 2.7; if higher, bitumen content can be reduced proportionately. In colder regions (max daily mean ≤30°C and min daily mean ≤-10°C), bitumen content may be increased by up to 0.5%. A tolerance of 0.3% by weight of mix is allowed for quality control (Clause 5).

These guidelines ensure proper mix design for durability and performance under varying climatic and traffic conditions.

Sources: Clause 3.1.1, Clause 3.4.2, Table 4

As per IRC 27 Clause 3.2 and 3.2.1, coarse aggregate shall be crushed rock, crushed gravel, or other hard material retained on a 2.36 mm sieve, clean, hard, durable, cubical in shape, and free from dust and deleterious substances. Clause 3.2.2 requires that for crushed gravel, at least 90% by weight retained on 4.75 mm sieve must have two fractured faces. The key physical properties and their requirements are summarized in Table 3 below:

• Aggregate must satisfy either Los Angeles Abrasion or Aggregate Impact Value test. ** If retained tensile strength is below 80%, use of anti-stripping agent is recommended.

These specifications ensure the aggregate's suitability for road construction as per IRC 27.

Sources: Clause 3.2, Clause 3.2.1, Clause 3.2.2, Table 3 Physical Properties of Coarse Aggregate

As per Clause 3.3 and Clause 2.36 of IRC 27, fine aggregate shall consist of crushed or naturally occurring mineral material passing the 2.36 mm sieve and retained on the 75 micron sieve. It must be clean, hard, durable, and free from dust, soft organic, and other deleterious substances. The proportion of rounded natural sand in the fine aggregate is limited to 10% if the bituminous mix (BM) is used within 100 mm from the road surface, and up to 50% if used more than 100 mm below the surface. This ensures proper mechanical interlock and durability. No specific formula is given, but these gradation and quality limits are critical for mix performance.

Sources: Clause 3.3, Clause 2.36

As per IRC 27 Clause 3.4 and 3.4.2, the combined aggregate grading must avoid gap grading by not varying from the lower limit on one sieve to the higher limit on the adjacent sieve. The aggregate grading and bitumen content requirements are given in Table 4 below:

*Nominal maximum aggregate size is the largest sieve size on which aggregate is retained.

**Bitumen content corresponds to aggregate specific gravity of 2.7; it can be adjusted proportionally for higher specific gravity. In colder regions (max daily mean ≤30°C and min daily mean ≤-10°C), bitumen content may be increased by 0.5%.

Additionally, Clause 3.4.1 requires grading tests per IS 2386 Part 1 (wet sieving).

For coarse aggregate physical properties and quality, refer to Clause 3.2.2 and Table 3, which specify cleanliness, particle shape, strength, durability, water absorption, and bitumen coating retention requirements.

This ensures a uniform, durable, and well-graded mix with appropriate bitumen content for pavement layers.

Sources: Clause 3.4, Clause 3.4.1, Clause 3.4.2, Table 4, Clause 3.2.2, Table 3

IRC 27 Clause 4 (Construction) specifies key quality control tests and equipment features for bituminous road construction. Table 7 lists control tests with minimum frequencies, including tests on bituminous binder, aggregate properties (impact value, abrasion, soundness, water absorption), mix grading, stripping, water sensitivity, temperature monitoring, binder content, spread rate, and density of compacted layers. For example, density tests are required once per 700 m² area, and binder content tests at least twice per 400 tonnes of mix (Clause 5.3).

Hot mix plants must have coordinated units for uniform mix, cold aggregate feed with minimum 4 bins and vibrators, variable speed conveyors with load sensors, dryers with burners, thermometric instruments, filler systems, dust control, and safety sirens (Annex A, Clause 4.2). Batch, continuous, and drum mix plants have specific gradation control, weighing, and mixing requirements.

Paver finishers require loading hoppers, hydrostatic drives, hydraulically extendable screeds with tamping/vibrating, electronic leveling, and internal screed heating (Annex A).

These specifications ensure consistent quality and safety during construction.

Sources: Clause 4, Clause 5.3, Table 7, Annex A (Clause 4.2)

Key specifications for Hot Mix Plants (HMP) per IRC 27 Annex A (Clause 4.2) include:

• Plant Type: Preferably batch mix with coordinated units producing uniform mix as per job mix formula.
• Cold Aggregate Feed: Minimum 4 bins with belt conveyors, vibrators for fines flow, variable speed drives, and electronic load sensors.
• Dryer Unit: Burner heating aggregates to required temperature without unburnt fuel or carbon residue, reducing moisture to specified minimum.
• Temperature Control: Thermometric instruments to record temperatures of heated aggregate, bitumen, and mix; temperature difference between aggregate and bitumen shall not exceed 15°C.
• Filler System: For bagged or bulk filler incorporation.
• Dust Control: Built-in system to recycle fines and prevent dust emission.
• Safety: Siren/horn for plant start-up.

For batch plants, gradation control with minimum four-deck vibratory screens, accurate weighing, and paddle mixer for homogeneous mix are essential.

Aggregate grading and bitumen content (Table 4):

Mixing and laying temperatures (Table 5):

The bitumen content may be adjusted based on aggregate specific gravity and climatic conditions. The plant must be calibrated periodically to ensure uniform quality. The difference between aggregate and bitumen temperature shall not exceed 15°C (Clause 4.2).

Sources: Clause 1.65, Annex A Clause 4.2, Clause 3.4.2, Table 4, Clause 4.4.3, Table 5

As per IRC 27 Clause 4.3 on Transportation, bituminous materials must be transported in clean, insulated, and covered vehicles to maintain quality. To prevent sticking and ease discharge, the interior of the vehicle may be treated with an asphalt release agent such as soap or limewater, provided it does not adversely affect the bituminous mix. No specific formulas or tables are provided in the retrieved context for transportation.

Sources: Clause 4.3

Key weather and seasonal limitations for laying bituminous macadam per IRC 27 Clause 4.4.1 are:

• Do not lay bituminous macadam if standing water is present, during rain, fog, dust storms, or if rain is imminent.
• Avoid laying when the base/binder course is damp.
• Air temperature on the surface must be at least 10°C.
• Wind speed at 2 m height must not exceed 40 km/h.

For bitumen selection based on climate (Clause 3.1.2 and Table 2):

Mixing, laying, and rolling temperatures (Table 5, Clause 4.4.3):

Rolling must be completed before the mat cools below the minimum rolling temperature.

These ensure proper laying conditions and material performance.

Sources: Clause 4.4.1, Clause 3.1.2, Table 2, Clause 4.4.3, Table 5

Key specifications for laying and compaction of bituminous macadam per IRC 27 are as follows:

• Laying (Clause 4.4.3):

  • Use self-propelled hydrostatic paver finisher with sensor for spreading, leveling, and tamping.
  • Continuous supply of asphalt mix to paver to ensure uniform flow without segregation.
  • Manual spreading in restricted areas or near expansion joints (stop machine 300 mm short).
  • Laying must be completed before mix temperature falls below specified limits.
  • Bituminous material >145°C shall not be laid on bridge decks without precautions.

• Temperature Limits (Table 5):

• Compaction (Clause 4.5.1 & 4.5.2):
  • Start compaction immediately after laying; complete before temperature falls below rolling temperature in Table 5.
  • Roll longitudinal joints immediately behind paver.
  • Rolling sequence: edges to center, or lower edge to upper edge for unidirectional camber.
  • Initial rolling with 8-10 tonnes dead weight or vibratory roller.
  • Intermediate rolling with 8-10 tonnes vibratory roller (amplitude 0.3-0.8 mm, frequency 30-50 Hz) or 12-15 tonnes pneumatic roller (tire pressure ≥0.56 MPa).
  • Finish rolling with 6-8 tonnes smooth wheel roller.
  • Continue rolling until ≥98% lab density (Marshall mould) is achieved or no further movement under roller for unspecified density.

These ensure uniform, durable pavement layers with proper density and surface finish.

Sources: Clause 4.4.3, Table 5, Clause 4.5.1, Clause 4.5.2

As per Clause 5.1, the surface finish requirements are specified but not detailed here. For surface evenness, Clause 5.2.1 mandates measurement using a 3 m straight edge following IRC:SP:16 procedures. According to Clause 5.2.3 and Table 6, the maximum permissible frequency of surface unevenness over a 300 m length in the longitudinal profile for Bituminous Macadam layers is:

This means for National Highways/State Highways (NH/SH), a maximum of 20 unevenness occurrences of 4-6 mm is allowed per 300 m, and for Major District Roads (MDR) and lower categories, up to 40 occurrences are permitted.

No specific formulas or joint specifications were provided in the retrieved context.

Sources: Clause 5.1, Clause 5.2.1, Clause 5.2.3, Table 6

As per IRC 27, the key specifications for surface finish include surface evenness and permissible unevenness frequency. Surface evenness is measured using a 3 m straight edge following IRC:SP:16 as stated in Clause 5.2.1. The maximum permissible frequency of surface unevenness over a 300 m length is given in Table 6 (Clause 5.2.3). For Bituminous Macadam layers, the allowable unevenness is between 4-6 mm. The maximum number of such unevenness occurrences allowed in 300 m is 20 for National Highways (NH) and State Highways (SH), and 40 for Major District Roads (MDR) and lower categories.

Sources: Clause 5.1, Clause 5.2, Clause 5.2.1, Clause 5.2.3, Table 6

As per IRC 27 Clause 5.2, surface evenness is measured using a 3 m straight edge following IRC:SP:16 (Clause 5.2.1). The maximum permissible surface unevenness in the longitudinal profile is 6 mm, and for the transverse profile camber, it is 4 mm (Clause 5.2.2). The maximum permissible frequency of surface unevenness over a 300 m length depends on the pavement layer and road category, as detailed in Table 6 (Clause 5.2.3). For Bituminous Macadam layers, the maximum number of unevenness (4-6 mm) allowed is 20 for National Highways/State Highways (NH/SH) and 40 for Major District Roads (MDR) and lower categories.

Sources: Clause 5.2.1, Clause 5.2.2, Clause 5.2.3, Table 6