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

The Introduction of IRC 63 outlines the evaluation of low-grade aggregates and soil-aggregate mixtures for pavement construction. Key specifications include tests listed in Tables 2 and 3 (not provided here) for suitability assessment. Table 6 provides criteria for soil-aggregate mixtures based on sieve designations per IS:460-1962, specifying the nominal maximum size and percentage by weight passing each sieve size. For example, for a nominal maximum size of 20 mm, 60-80% should pass the 80 mm sieve, 80-100% the 40 mm sieve, and 100% the 20 mm sieve, with gradation continuing down to 75 micron. These gradation limits ensure proper particle size distribution for pavement materials. Physical requirements are further detailed in Clause 5.1 (not included here).

Sources: Clause 4.1, Table 6

The classification and characteristics of low-grade aggregates as per IRC 63 are summarized in the following tables and clauses:

TABLE 1. LOW GRADE AGGREGATES

• This table categorizes aggregates based on their physical and mechanical properties.

TABLE 2. TESTING OF LOW GRADE AGGREGATES

• Specifies the tests required to evaluate the suitability of low-grade aggregates, including strength, durability, and grading tests.

Clause 3: COMMON TYPES OF LOW GRADE AGGREGATES

• Lists typical low-grade aggregates such as crusher dust, quarry waste, and natural gravel with impurities.

Clause 5: CRITERIA FOR USE OF LOW GRADE AGGREGATES

• Defines permissible limits for properties like water absorption, crushing value, and grading to ensure performance in construction.

These tables and criteria guide the selection and testing of low-grade aggregates to ensure structural adequacy and durability in road construction.

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

As per IRC 63, Clause 3.1 and Table 1, common types of low-grade aggregates encountered in India include various materials with variable quality, such as Dhandla. The selection should be based on actual physical characteristics rather than just nomenclature. Table 1 lists these types, while Table 2 provides testing methods for low-grade aggregates to assess their suitability. Key points:

• Low-grade aggregates vary widely in quality.
• Physical testing is essential for selection.
• Typical types are enumerated in Table 1.
• Testing procedures are detailed in Table 2.

This ensures appropriate use in construction despite variability in aggregate quality.

Sources: Clause 3.1, TABLE 1, TABLE 2

For testing low-grade aggregates and soil-aggregate mixtures as per IRC 63, Clause 4, the key tests are summarized in Tables 2 and 3 respectively. These tables list appropriate tests to evaluate suitability for pavement construction. Unfortunately, the exact test names and parameters from Tables 2 and 3 are not provided in the retrieved context. Generally, such tests include particle size distribution, plasticity index, strength tests, and durability assessments for aggregates and mixtures. For precise test methods and criteria, refer directly to Tables 2 and 3 in IRC 63, Clause 4.

Sources: Clause 4.1, Table 2, Table 3

The key physical requirements for low-grade aggregates as per IRC 63 are summarized in Table 5.1, which specifies the maximum Wet Aggregate Impact Value (AIV) for different construction types: Sub-base (max 50%), Base course with bituminous surfacing (max 40%), and Surfacing course (max 30%) tested according to IS:5640-1970. Additionally, soil-aggregate mixtures must conform to grading limits per sieve sizes as per IS:460-1962, detailed in the grading table for nominal maximum sizes ranging from 80 mm to 5 mm. This ensures proper particle size distribution for stability and durability. These physical requirements ensure aggregates meet strength and gradation criteria essential for road construction layers.

Sources: TABLE 4. PHYSICAL REQUIREMENTS OF LOW GRADE AGGREGATES, TABLE 6. CRITERIA FOR USE OF SOIL-AGGREGATE MIXTURES

The key criteria for use of soil-aggregate mixtures as per IRC 63 are specified in the grading limits table based on sieve designations (IS:460-1962). The nominal maximum size of material ranges from 80 mm down to 5 mm, with corresponding percentage passing limits for each sieve size. For example, for a nominal size of 80 mm, 100% passes the 80 mm sieve; for 40 mm nominal size, 80-100% passes 80 mm sieve and 100% passes 40 mm sieve, and so forth. The detailed grading limits are given in the following table, which guides the selection and proportioning of soil-aggregate mixtures to ensure proper gradation and performance in pavement layers.

Sources: TABLE: 6. CRITERIA FOR USE OF SOIL-AGGREGATE MIXTURES

Key pavement design considerations per IRC 63 include:

• Soil-Aggregate Mixtures: Should be evaluated by Plasticity Index (PI), gradation, and soaked CBR value as per IS:2720 (Part XVI)-1965. For sub-base, CBR should be at least 20; for base courses on heavily trafficked roads, CBR is normally 80 but may be lower for arid or light traffic areas (Clause 6.3).

• Thickness of Flexible Pavements: Designed per IRC:37-1970. Minimum thickness for low-grade aggregates or soil-aggregate mixtures is 10-15 cm; for moorum, minimum 15 cm (Clause 7.1).

• Sub-base for Rigid Pavements: Design guidance from IRC:58-1974 (Clause 7.2).

• Construction Practices: Low-grade aggregates should be laid on well-compacted subgrade and the road kept well drained (Clause 7.3).

• Gradation: Not less than 10% material should be retained between each pair of successive sieves except for the larger pair (Clause 1.18).

These form the core specifications and design parameters for pavement layers using low-grade materials.

Sources: Clause 1.18, Clause 6.3, Clause 7.1, Clause 7.2, Clause 7.3

For gradation and particle size distribution in soil-aggregate mixtures as per IRC 63, the material should be smoothly graded to achieve maximum dry density, guided by Fuller's grading rule (Clause 6.2). Typical grading limits for general applications are provided in Table 5, with the first three gradings suited for base courses and the last two for both base course and surfacing. The sieve designations and corresponding percentage passing by weight for different nominal maximum sizes are given in the following table (from IS:460-1962):

Gradation tests should be conducted as per IS:2720 (Part IV)-1965. This ensures the soil-aggregate mixture meets the criteria for strength and durability in pavement layers.

Sources: Clause 6.2, Table 5, IS:460-1962, IS:2720 (Part IV)-1965

For stabilization and processing methods in IRC 63, key specifications include the use of CBR (California Bearing Ratio) tests on samples soaked for 4 days as per IS:2720 (Part XVI)-1965, especially for moorum or soil-aggregate admixtures. The gradation of soil-aggregate mixtures must conform to the sieve passing percentages given in the following table (from IS:460-1962), which ensures proper particle size distribution for stability:

These gradation limits help achieve the desired strength and durability in soil-aggregate mixtures. The CBR test on soaked samples evaluates the strength after water exposure, critical for pavement design.

No explicit formulas were provided in the retrieved context.

Sources: IS:2720 (Part XVI)-1965, IS:460-1962, TABLE: 6. CRITERIA FOR USE OF SOIL-AGGREGATE MIXTURES

For drainage and compaction in IRC 63, key guidelines include: 1) Use smoothly graded materials to achieve maximum dry density, guided by Fuller's grading rule (Clause 6.2). 2) Typical gradings for soil-aggregate mixtures are given in Table 5, with the first three suited for base courses and the last two for both base and surfacing. 3) Table 6 provides sieve-wise grading criteria for soil-aggregate mixtures, specifying percent passing for nominal maximum sizes from 80 mm to 5 mm. 4) Not less than 10% material should be retained between successive sieves except for the largest pair (Clause 1.18). 5) Soaked CBR values should be ≥20 for sub-base and about 80 for base courses on heavily trafficked roads (Clause 6.3). 6) Minimum thickness for flexible pavement courses using low-grade aggregates is 10-15 cm, and 15 cm for moorum (Clause 7.1). 7) Proper drainage and well-compacted subgrade are essential when using low-grade aggregates (Clause 7.3).

Sources: Clause 6.2, Clause 1.18, Clause 6.3, Clause 7.1, Clause 7.3, Table 6

For sulphate-infested areas, special consideration is given to the aggregates used in construction. As per the context, the Sodium sulphate soundness test (IS:2386 Part V-1963) must be conducted on aggregates intended for use in such areas to assess their durability against sulphate attack. Additionally, soil-aggregate mixtures should conform to grading criteria specified in the provided sieve analysis table (IS:460-1962) to ensure proper particle size distribution and performance. This table outlines the percentage by weight passing various sieve sizes for nominal maximum sizes of material ranging from 80 mm to 5 mm, which is critical for pavement construction in aggressive environments. These tests and criteria help ensure the materials' resistance to chemical degradation and mechanical stability in sulphate-rich soils.

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

For references and test methods in IRC 63 regarding low-grade aggregates and soil-aggregate mixtures, key points include:

• Samples must be representative and collected per IS:2430-1969 (sampling procedure).

• Table 6 provides criteria for soil-aggregate mixtures based on sieve designations (IS:460-1962), specifying the nominal maximum size and percentage passing each sieve size. This ensures proper gradation for pavement construction.

Here is the reproduced Table 6 for gradation criteria:

• Table 3 (not fully shown) lists tests appropriate for evaluating suitability of these materials.

These ensure materials meet gradation and quality standards for pavement use as per IRC 63.

Sources: Clause None: Note, TABLE: 6. CRITERIA FOR USE OF SOIL-AGGREGATE MIXTURES

The Specifications & Standards Committee for IRC 63 included key members such as J.S. Marya (Convenor), T.K. Natarajan (Member-Secretary), and many others listed in the committee table. The draft guidelines were processed in meetings held in 1974 and approved by the Executive Committee and Council by early 1976. A critical table provided is the "Criteria for Use of Soil-Aggregate Mixtures" based on IS:460-1962 sieve designations, specifying nominal maximum sizes and percentage passing by weight for various sieve sizes. This table guides the gradation requirements for soil-aggregate mixtures used in road construction where hard aggregates are scarce or costly. The table is reproduced below for clarity:

This committee and table provide foundational guidance for using low-grade aggregates economically in road construction where hard aggregates are unavailable or expensive.

Sources: TABLE: 1. INTRODUCTION, TABLE: 6. CRITERIA FOR USE OF SOIL-AGGREGATE MIXTURES