Tentative Guidelines for the Use of Low-Grade Aggregates and Soil Aggregates Mixtures in Road Pavement Construction
1976 Edition

The overview section of IRC 63 presents the assessment framework for low-quality aggregates and soil-aggregate blends in pavement construction. It references testing protocols outlined in Tables 2 and 3 (not included) for suitability evaluation. Table 6 specifies grading requirements for soil-aggregate blends according to IS:460-1962 sieve designations, indicating nominal maximum sizes and corresponding weight percentages passing each sieve. For instance, for a nominal size of 20 mm, 60-80% must pass the 80 mm sieve, 80-100% the 40 mm sieve, and 100% the 20 mm sieve, continuing down to 75 microns. These gradation parameters ensure optimal particle size distribution for pavement layers. Additional physical property requirements are described in Clause 5.1 (details not provided).

References: Clause 4.1, Table 6

This section summarizes the classification and characteristics of low-quality aggregates as per IRC 63:

TABLE 1. LOW-QUALITY AGGREGATES

• Categorizes aggregates based on physical and mechanical attributes.

TABLE 2. TEST PROCEDURES FOR LOW-QUALITY AGGREGATES

• Lists essential tests to assess strength, durability, and gradation.

Clause 3: COMMON LOW-QUALITY AGGREGATE TYPES

• Identifies typical materials such as crusher dust, quarry residues, and natural gravels with impurities.

Clause 5: USAGE CRITERIA FOR LOW-QUALITY AGGREGATES

• Defines acceptable limits for parameters like water absorption, crushing strength, and grading to ensure construction performance.

These classifications and criteria support informed selection and testing to guarantee structural integrity and longevity in roadworks.

References: TABLE 1, TABLE 2, Clause 3, Clause 5

According to IRC 63, Clause 3.1 and TABLE 1, prevalent types of low-quality aggregates found in India include materials of varying consistency, such as Dhandla. Selection should be grounded in actual physical properties rather than just names. TABLE 1 enumerates these types, while TABLE 2 details testing methods to evaluate their suitability. Key points include:

• Wide variability in quality among low-quality aggregates.
• Necessity of physical testing for selection.
• Enumeration of typical types in TABLE 1.
• Testing procedures specified in TABLE 2.

This approach ensures appropriate application despite the inherent variability in aggregate quality.

References: Clause 3.1, TABLE 1, TABLE 2

Per IRC 63, Clause 4, testing protocols for low-quality aggregates and soil-aggregate blends are summarized in TABLES 2 and 3 respectively. These tables specify relevant tests to determine suitability for pavement use. Although exact test names and criteria from these tables are unavailable here, typical assessments include particle size distribution, plasticity index, strength, and durability evaluations. For comprehensive test methods and criteria, refer directly to IRC 63, Clause 4, TABLES 2 and 3.

References: Clause 4.1, TABLE 2, TABLE 3

Physical property requirements for low-quality aggregates are summarized in TABLE 5.1 of IRC 63, specifying maximum allowable Wet Aggregate Impact Values (AIV) for various construction layers: Sub-base (up to 50%), Base course with bituminous surfacing (up to 40%), and Surfacing course (up to 30%), following IS:5640-1970 testing standards. Soil-aggregate blends must meet grading specifications per IS:460-1962 sieve sizes, detailed for nominal maximum sizes ranging from 80 mm to 5 mm. These requirements ensure appropriate particle size distribution supporting stability and durability essential for pavement layers.

References: TABLE 4, TABLE 6

IRC 63 stipulates grading criteria for soil-aggregate blends based on sieve designations from IS:460-1962. Nominal maximum particle sizes range from 80 mm to 5 mm, with corresponding weight percentages passing each sieve. For example, an 80 mm nominal size requires 100% passing the 80 mm sieve; a 40 mm size requires 80-100% passing 80 mm and 100% passing 40 mm sieves, etc. This grading table guides the selection and proportioning of soil-aggregate mixtures to achieve proper gradation and satisfactory pavement performance.

References: TABLE 6

Pavement design recommendations from IRC 63 include:

• Soil-aggregate blends should be assessed using Plasticity Index, gradation, and soaked California Bearing Ratio (CBR) tests per IS:2720 (Part XVI)-1965. For sub-base, a minimum CBR of 20 is recommended; base courses on heavily trafficked roads typically require about 80, though less may be accepted in dry or low-traffic regions (Clause 6.3).

• Flexible pavement thickness should follow IRC:37-1970, with minimum layer thicknesses of 10-15 cm for low-quality aggregates or soil-aggregate mixes; moorum requires a minimum of 15 cm (Clause 7.1).

• Sub-base design for rigid pavements is guided by IRC:58-1974 (Clause 7.2).

• Construction practice mandates placement on well-compacted subgrade and ensuring adequate drainage (Clause 7.3).

• Gradation should maintain at least 10% retention between successive sieves except the largest pair (Clause 1.18).

These parameters form the core design framework for pavements utilizing low-quality materials.

References: Clauses 1.18, 6.3, 7.1, 7.2, 7.3

Soil-aggregate mixtures should be smoothly graded to maximize dry density, guided by Fuller's curve, as per IRC 63 Clause 6.2. TABLE 5 provides typical gradation limits: the first three gradings apply to base courses, the last two cover base and surfacing layers. Sieve size designations and percentage passing by weight for nominal maximum sizes are provided according to IS:460-1962, ranging from 80 mm to 5 mm. Gradation testing should follow IS:2720 (Part IV)-1965 to confirm compliance. This ensures mixtures possess adequate strength and durability for pavement applications.

References: Clause 6.2, TABLE 5, IS:460-1962, IS:2720 (Part IV)-1965

IRC 63 recommends stabilization techniques including soaked CBR testing (4-day soak) per IS:2720 (Part XVI)-1965, especially for moorum or soil-aggregate blends. Gradation must conform to sieve passing percentages outlined in IS:460-1962 to achieve required stability and strength. These gradation parameters support durability and performance after exposure to moisture. Although no exact formulas are given, adherence to these criteria is critical for effective stabilization and pavement longevity.

References: IS:2720 (Part XVI)-1965, IS:460-1962, TABLE 6

For drainage and compaction, IRC 63 specifies:

1. Use of smoothly graded materials per Fuller's grading rule to achieve maximum dry density (Clause 6.2).
2. Typical gradations for soil-aggregate mixtures are in TABLE 5; first three suited for base courses, last two applicable to base and surfacing.
3. Grading limits for soil-aggregate blends per sieve sizes and nominal maximum sizes detailed in TABLE 6.
4. Minimum 10% retention between successive sieves except for the largest pair (Clause 1.18).
5. Soaked CBR values of ≥20 for sub-base and about 80 for base layers on busy roads (Clause 6.3).
6. Minimum thicknesses for flexible pavement layers: 10-15 cm for low-quality aggregates, 15 cm for moorum (Clause 7.1).
7. Placement over well-drained, compacted subgrade is mandatory (Clause 7.3).

These practices ensure durability and structural performance.

References: Clauses 6.2, 1.18, 6.3, 7.1, 7.3, TABLE 6

In areas with sulphate-rich soils, aggregates must undergo Sodium sulphate soundness testing as per IS:2386 (Part V)-1963 to evaluate resistance to sulphate attack. Soil-aggregate blends should also adhere to grading specifications from IS:460-1962 to maintain appropriate particle size distribution for durability. These protocols help ensure chemical resistance and mechanical stability of pavement materials in aggressive environments.

References: IS:2386 (Part V)-1963, IS:460-1962

Key reference standards and testing procedures include:

• Sample collection must comply with IS:2430-1969 guidelines.

• Grading criteria for soil-aggregate mixtures detailed in TABLE 6 (IS:460-1962) specify nominal maximum sizes and corresponding sieve passing percentages.

• Testing methods suitable for evaluating aggregate and mixture suitability are listed in TABLE 3 (not fully shown).

These ensure compliance with quality and gradation requirements necessary for pavement construction using low-quality materials.

References: TABLE 6, IS:2430-1969

The IRC 63 Specifications & Standards Committee comprised members such as J.S. Marya (Convenor), T.K. Natarajan (Member-Secretary), among others. Draft guidelines were developed through meetings in 1974 and ratified by the Executive Committee and Council by early 1976. A pivotal resource is the grading criteria table for soil-aggregate mixtures based on IS:460-1962 sieve designations, detailing nominal maximum particle sizes and percentage passing by weight. This foundational table assists in applying low-quality aggregates economically where hard aggregates are inaccessible or costly.

References: TABLE 1, TABLE 6