IRC 55-1974 provides recommended practices for designing and constructing sand-bitumen base courses primarily for road pavements in desert and sandy regions like Rajasthan. It covers the selection of materials, mix design using bituminous binders, construction procedures, and quality control to ensure durable base layers where conventional aggregates are scarce. This standard is essential for engineers working on pavement bases using sand stabilized with penetration grade or cut-back bitumens.
Overview
IRC 55-1974 provides recommended practices for designing and constructing sand-bitumen base courses primarily for road pavements in desert and sandy regions like Rajasthan. It covers the selection of materials, mix design using bituminous binders, construction procedures, and quality control to ensure durable base layers where conventional aggregates are scarce. This standard is essential for engineers working on pavement bases using sand stabilized with penetration grade or cut-back bitumens.
Audience
Contents
Structure
The IRC 55 code introduction and key specifications for sand-bitumen mix include:
The mix design is based on the Hubbard Field Stability Method.
Sources: Clause 4.75, Clause 5.1, Clause 5.2, Clause 6.3, Clause 6.5, Clause 7
The scope of IRC 55 covers the design and construction of sand-bitumen mixes for road bases. Key specifications include: the sand-bitumen mix must be designed using the Hubbard Field Stability Method (Clause 3). Coarse aggregates should be gravel or kankar, clean, retaining on 4.75 mm IS sieve, with max size not exceeding one-third of compacted layer thickness (Clause 4.75). Bitumen used shall conform to IS 73-1961 or IS 217-1961 (Clause 4.75). The bitumen type depends on sand type and atmospheric conditions (Clause 5.1). Bitumen proportion is designed to meet mix requirements (Clause 5.2). Construction involves heating bitumen to specific temperatures (150°-165°C for penetration grade, 80°-120°C for cutbacks) and sand to 135°-163°C (Clause 6.3). Mix is laid to compacted thickness of 10 cm from loose 15 cm (Clause 6.5). Rolling and curing procedures vary with bitumen type (Clause 6.5, 6.8). Wearing surface of 20 mm premix carpet is recommended (Clause 7). Quality control includes temperature difference limits, density tests (≥95% lab density), mix tests, and surface smoothness checks (Clause 7).
Sources: Clause 3, Clause 4.75, Clause 5.1, Clause 5.2, Clause 6.3, Clause 6.5, Clause 6.8, Clause 7
The design criteria for sand-bitumen mix per IRC 55 include: 1) The mix should be designed using the Hubbard Field Stability Method and meet specified requirements, with a preference for voids percentage on the lower side (Clause 3). 2) Coarse aggregates must be gravel or kankar, clean, free from fines/clay, retained on 4.75 mm IS sieve, and max size not exceeding 1/3 of compacted layer thickness (Clause 4.75). 3) Binder shall be paving bitumen or cut-back bitumen conforming to IS 73-1961 or IS 217-1961 (Clause 4.75). 4) Bitumen type selection depends on sand type and atmospheric conditions (Clause 5.1). 5) Bitumen proportion is designed to satisfy mix requirements (Clause 5.2). 6) Heating temperatures: penetration grade bitumen at 150°-165°C, cut-back bitumen at 80°-120°C; sand heated to 135°-163°C if needed (Clause 6.3). 7) Mix laid to loose thickness up to 15 cm, compacted to 10 cm, with uniform density and curing times depending on bitumen type (Clause 6.5). 8) Quality control includes temperature difference ≤14°C, density ≥95% of lab density, stability and voids tests, and surface smoothness within 6 mm over 3 m straight edge (Clause 6 and 7).
Sources: Clause 3, Clause 4.75, Clause 5.1, Clause 5.2, Clause 6.3, Clause 6.5, Clause 7
Key material specifications and procedures from IRC 55 for sand-bitumen mixes are as follows:
The sand-bitumen mix design should satisfy Hubbard Field Stability Method requirements.
Sources: Clause 4.1.1, Clause 4.75, Clause 5.1, Clause 6.3.1, Clause 6.3.2, Clause 6.5, Clause 6.8
The design of sand-bitumen mix per IRC 55 involves the following key points:
Aggregate Requirements: Maximum 25% by weight of coarse aggregates (gravel or kankar), retained on 4.75 mm IS sieve, max size ≤ 1/3 compacted layer thickness (Clause 4.75).
Binder: Use paving bitumen (penetration grade) or cut-back bitumen conforming to IS 73-1961 or IS 217-1961.
Bitumen Selection: Depends on sand type and atmospheric conditions (Clause 5.1).
Bitumen Proportion: Designed to satisfy mix requirements (Clause 5.2).
Mixing: Use twin shaft paddle mixer; mix time 1-2 minutes.
Heating: Binder heated to viscosity 150-300 cSt (penetration grade: 150-165°C; cut-back: 80-120°C). Sand heated to 135-163°C if needed (Clause 6.3).
Laying: Loose thickness up to 15 cm, compacted to 10 cm; rolling starts immediately for penetration bitumen, after curing (1-7 days) for cut-back bitumen (Clause 6.5).
Quality Control: Temperature difference between sand/aggregate and binder ≤14°C; density ≥95% of lab density; stability and voids tested per 50 m³; surface irregularities ≤6 mm (Clause 6).
Wearing Surface: 20 mm premix carpet as per IRC 14-1977 (Clause 7).
Design Method: Hubbard Field Stability Method or Modified Hubbard for kankar mixes.
This ensures a durable, well-compacted sand-bitumen base layer suitable for road construction.
Sources: Clause 4.75, Clause 5.1, Clause 5.2, Clause 6.3, Clause 6.5, Clause 7
Key construction specifications from IRC 55 include:
Coarse Aggregates: Gravel or kankar, clean, free from fines/clay, retained on 4.75 mm IS sieve, max size ≤ 1/3 compacted layer thickness (Clause 4.75).
Binder: Paving bitumen or cut-back bitumen per IS 73-1961 or IS 217-1961 (Clause 4.75).
Grooves: 8 cm wide, 5 cm deep at edges for thickened edge strength (Clause 6).
Heating: Binder heated to viscosity 150-300 cSt; penetration grade bitumen at 150°-165°C, cut-back at 80°-120°C; sand and aggregates heated to 135°-163°C if needed (Clause 6.3).
Mixing: Twin shaft paddle mixer, 1-2 minutes mixing time; mix laid immediately (Clause 6.3).
Laying: Loose thickness up to 15 cm compacted to 10 cm; uniform density required (Clause 6.5).
Rolling: For penetration bitumen, roll hot mix immediately; for cut-back, initial rolling after curing 1-7 days; final rolling with 8-10 tonne smooth roller until desired density (Clause 6.5).
Opening to Traffic: After 24 hours of final rolling; light pneumatic vehicles initially; normal traffic after 1 month; wearing surface within 3 months (Clause 6.8).
Wearing Surface: 20 mm premix carpet as per IRC 14-1977 (Clause 7).
Quality Control: Temperature difference between sand/aggregate and binder ≤14°C; density ≥95% of lab density; mix tests every 50 m³; surface irregularities ≤6 mm (Clause 6).
These ensure durable, well-compacted bituminous layers with proper curing and quality control.
Sources: Clause 4.75, Clause 5.1, Clause 6.3, Clause 6.5, Clause 6.8, Clause 7
Key specifications for laying the wearing surface as per IRC 55 include:
These guidelines ensure durability and performance of the wearing surface over sand-bitumen bases.
Sources: Clause 7, Clause 6.5, Clause 4.75
Key quality control specifications per IRC 55 include:
Temperature Control: The temperature difference between sand/aggregate and binder shall not exceed 14°C during mixing (Clause 6).
Density Control: For every 500 m² or less of compacted surface, one field density test is required. The density must be at least 95% of the laboratory-designed density (Clause 6).
Mix Testing: At least one sample per 50 m³ of mix or minimum two samples per shift must be tested for stability, voids, and binder content (Clause 6).
Surface Smoothness: Finished surface tested with a 3 m straight edge; irregularities over 6 mm must be corrected (Clause 6).
Material Specifications: Coarse aggregates must be clean, free from fines/clay, retained on 4.75 mm sieve, max size ≤ 1/3 compacted layer thickness (Clause 4.75).
Binder Heating: Penetration grade bitumen heated to 150–165°C; cut-back bitumen to 80–120°C; sand and aggregates heated as needed (Clause 6.3).
Mixing Time: Typically 1–2 minutes using twin shaft paddle mixer (Clause 6.3).
These controls ensure uniformity, strength, and durability of the sand-bitumen mix base layer.
Sources: Clause 4.75, Clause 5.1, Clause 6.3, Clause 6.5, Clause 6.8
As per IRC 55, Clause 6.8, the sand-bitumen base course can be opened to traffic after 24 hours of completing the final rolling operation, initially allowing only light pneumatic-tyred vehicles. Normal traffic may be permitted only after one month. The final wearing surface, typically a 20 mm thick premix carpet as per IRC 14-1977, should be laid within three months to protect the base and provide a running surface.
Key specifications include:
These ensure adequate strength and durability before opening to traffic.
Sources: Clause 4.75, Clause 5.1, Clause 6.3, Clause 6.5, Clause 6.8, Clause 7
The IRC 55 code was approved by the Specifications and Standards Committee (31 Jan - 1 Feb 1974), Executive Committee (1 May 1974), and Council (2 May 1974). Key specifications include: use of paving bitumen conforming to IS 73-1961 or IS 217-1961; coarse aggregates must be clean gravel or kankar, retained on 4.75 mm sieve, max size ≤ 1/3 compacted layer thickness (Clause 4.75). Binder heating temperatures: 150°-165°C for penetration grade bitumen, 80°-120°C for cut-back bitumen (Clause 6.3.1). Mix laying thickness: loose up to 15 cm, compacted to 10 cm (Clause 6.5). Rolling and curing procedures differ for penetration and cut-back bitumen (Clause 6.5). Traffic opening after 24 hours post final rolling; normal traffic after 1 month (Clause 6.8). Wearing surface: 20 mm premix carpet as per IRC 14-1977 (Clause 7). Quality control includes temperature difference ≤14°C, density ≥95% lab density, and surface smoothness within 6 mm (Clause 7).
Sources: Clause 4.75, Clause 5.1, Clause 6.3.1, Clause 6.5, Clause 6.8, Clause 7
Frequently Asked
For sand-bitumen base courses, the recommended types of bitumen include penetration grade bitumens, cut-back bitumens, and other special road oils. These materials are used to stabilize sand layers either directly over sandy subgrade or on a prepared base or sub-base of the pavement, as per the recommended practice outlined in IRC 55.
Sources: IRC 55, Recommended Practice for Sand-Bitumen Base Courses
As per IRC 55, sand used should be clean dune or pit sand, free from organic and deleterious materials, with no more than 10% passing the 75-micron sieve by weight (Clause 4.1.1). Coarse aggregates must be clean gravel or kankar, free from fines and clayey matter, retaining on the 4.75 mm IS sieve, with maximum size not exceeding one-third of the compacted layer thickness (Clause 4.75). Sand and aggregates should be dry and, if necessary, warmed to 135°-163°C when using penetration grade bitumen (Clause 6.3.2). Mixing is done in a twin-shaft paddle mixer for 1-2 minutes, ensuring uniform distribution of binder and aggregates (Clause 6.3.2).
Sources: Clause 4.1.1, Clause 4.75, Clause 6.3.2
The key mix design parameters using the Hubbard Field Stability Method as per IRC 55 are:
These parameters ensure the mix has adequate stability under specified temperature conditions, critical for pavement performance.
Sources: Clause None
As per IRC 55, the recommended procedures for heating and mixing materials are as follows: The binder (bitumen) shall be heated to a temperature where its viscosity is between 150-300 centistokes, typically 150°-165°C for penetration grade bitumen and 80°-120°C for cut-back bitumen (Clause 6.3.1). Sand and aggregates must be dry and, if required, heated to 135°-163°C when using penetration grade bitumen, preferably using a tilting drum drier (Clause 6.3.2). Mixing is done using a twin shaft paddle type mixer with designed quantities of aggregates and binder; mixing time is generally 1 to 2 minutes based on initial trials (Clause 6.3.2). The mix should be laid immediately after mixing to ensure quality. Additionally, temperature difference between sand/aggregate and binder should not exceed 14°C to maintain mix integrity (Clause 7).
Sources: Clause 6.3.1, Clause 6.3.2, Clause 7
When using cut-back bitumen, the mix after laying should be allowed to cure before initial rolling. The curing period may vary from 1 to 7 days depending on the type of cut-back bitumen and prevailing weather conditions, as per Clause 6.5. The curing time starts from the time of preparing the mix until the mix crumbles under light finger pressure and the solvent smell is minimal. Initial rolling should begin at least 24 hours after laying. Final rolling with a smooth wheel roller continues until the desired density is achieved, which may take up to a week for cut-back bitumen mixes, according to Clause 6.5.
Sources: Clause 6.5
Ask AI about any clause, requirement, or provision in IRC 55. Get instant, clause-cited responses powered by our indexed library.
Free tier includes 150 queries (50 AI + 100 Reference) · No credit card required