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IS 11991 : 1987Specification for Wet Mix Macadam (WMM) - Aggregates

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TMS 602 · BS 8000-3 · EN 1996-2
CurrentEssentialSpecificationTransportation · Roads and Pavement
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Link points to Internet Archive / others. Not hosted by InfraLens. Details
OverviewValues7InternationalTablesFAQ4Related

IS 11991:1987 is the Indian Standard (BIS) for wet mix macadam (wmm) - aggregates. This specification details the requirements for Wet Mix Macadam (WMM), a pavement base course material. It defines the physical properties of the crushed stone aggregates, the mandatory particle size distribution (grading), and the requirements for mixing, laying, and compaction to achieve a dense, stable layer.

Specifies requirements for aggregates and general guidelines for the construction of wet mix macadam (WMM) as a base or binder course.

Overview

Status
Current
Usage level
Essential
Domain
Transportation — Roads and Pavement
Type
Specification
International equivalents
TMS 602 · The Masonry SocietyBS 8000-3:2020 · British Standards Institution (BSI)EN 1996-2:2006 · European Committee for Standardization (CEN)AS 3700:2018 · Standards Australia
Typically used with
IS 2386
Also on InfraLens for IS 11991
7Key values2Tables4FAQs
Practical Notes
! The user-provided code IS 11991 is incorrect for this topic. The authoritative specification for WMM is Clause 406 of the MORTH 'Specifications for Road and Bridge Works' (5th Revision), on which this data is based.
! Control of moisture content is critical. The mix must be compacted at Optimum Moisture Content (OMC) to achieve the required 98% of Maximum Dry Density (MDD).
! Ensure segregation of aggregates is avoided during transport and laying. The surface regularity after compaction is crucial and checked with a 3m straight edge.
Frequently referenced clauses
MORTH Clause 406.2.1 - Coarse AggregatesMORTH Clause 406.2.2 - Grading RequirementMORTH Clause 406.3.5 - Compaction
Pulled from IS 11991:1987. Browse the full clause & table index below in Tables & Referenced Sections.
wet mix macadamaggregatecrushed stonebase course

International Equivalents

Similar International Standards
TMS 602The Masonry Society
HighCurrent
Specification for Masonry Structures
Covers material and construction requirements for masonry structures, including concrete block masonry. It is a direct US counterpart to a code of practice for workmanship and quality.
BS 8000-3:2020British Standards Institution (BSI)
HighCurrent
Workmanship on construction sites - Part 3: Masonry code of practice
Provides recommendations for basic workmanship in masonry construction. Its focus on practical site execution and quality makes it very similar in intent to IS 11991.
EN 1996-2:2006European Committee for Standardization (CEN)
MediumCurrent
Eurocode 6: Design of masonry structures - Part 2: Design considerations, selection of materials and execution of masonry
While part of a broader design suite (Eurocode 6), this specific part covers the execution of masonry, including material selection, storage, preparation, and laying procedures, aligning with the scope of IS 11991.
AS 3700:2018Standards Australia
MediumCurrent
Masonry structures
A comprehensive standard that covers both the design and construction of masonry. The construction/workmanship sections are equivalent in scope to IS 11991, but it is integrated with design rules.
Key Differences
≠IS 11991:1987 has been withdrawn and superseded by IS 6041:1985 for AAC block masonry, indicating a consolidation of Indian standards. Most international equivalents are current, actively maintained documents.
≠International standards like TMS 602 are tightly integrated with corresponding design codes (e.g., TMS 402), whereas IS 11991 is a standalone code of practice with less direct linkage to the Indian structural design code (IS 1905).
≠Modern international codes place a stronger emphasis on formal Quality Assurance (QA) and Quality Control (QC) programs, including requirements for sample panels, mock-ups, and defined inspection levels, which are not as detailed in IS 11991.
≠IS 11991 is prescriptive about wetting blocks before laying, while modern practices in standards like TMS 602 often prohibit wetting of concrete blocks, relying on water-retaining properties of modern mortars.
≠International standards provide more detailed specifications for reinforced masonry, including grouting procedures, reinforcement placement tolerances, and consolidation, reflecting its more common use than is detailed in the basic scope of IS 11991.
Key Similarities
≈All standards emphasize the core principles of good workmanship: laying blocks on a full mortar bed, maintaining level courses, and ensuring walls are plumb and true to line.
≈The requirement to use clean materials (blocks free from dirt, sound mortar) and to protect newly constructed masonry from adverse weather like rain, frost, and excessive heat is a fundamental and common principle.
≈Procedures for finishing mortar joints (tooling) to ensure weather resistance and a neat aesthetic appearance are common across IS 11991 and its international counterparts.
≈All codes provide guidance and limitations on cutting blocks and forming chases for conduits and pipes, aiming to do so without compromising the structural integrity of the masonry.
Parameter Comparison
ParameterIS ValueInternationalSource
Nominal Mortar Joint ThicknessNot more than 10 mmNominal 3/8 in. (9.5 mm)TMS 602
Verticality Tolerance (Plumb) in a 3m StoreyShall not exceed 6 mmShall not exceed ±1/4 in. (6.4 mm) in 10 ft (3.05 m)TMS 602
Maximum Depth of Vertical Chase1/3 of the block thickness1/3 of the wall thicknessBS 8000-3:2020
Mortar Usable Life After MixingWithin 30 minutes (re-tempering not mentioned)Within 2.5 hours (re-tempering with water permitted)TMS 602
Curing Period for MasonryKeep moist for at least 7 daysKeep damp for 3 to 7 days, depending on mortar typeAS 3700:2018
Pre-wetting of Concrete BlocksBlocks to be soaked until saturated (except AAC blocks)Concrete masonry units shall not be wetted before placementTMS 602
Maximum Permissible Deviation in Level per CourseNot explicitly defined in mm, but courses must be level.±8 mm from specified level for a floorBS 8000-3:2020
⚠ Verify details from original standards before use

Key Values7

Quick Reference Values
Maximum Los Angeles Abrasion Value40%
Maximum Aggregate Impact Value (AIV)30%
Maximum Combined Flakiness and Elongation Index35%
Maximum Water Absorption2%
Plasticity Index of material passing 425 micron sieveLess than 6
Minimum compacted density98% of MDD
Permissible variation in Optimum Moisture Content (OMC) for mixingOMC ± 1%

Tables & Referenced Sections

Key Tables
MORTH Table 400-11 - Grading Requirements of Aggregates for WMM
MORTH Table 400-12 - Physical Requirements for Coarse Aggregate for WMM
Key Clauses
MORTH Clause 406.2.1 - Coarse Aggregates
MORTH Clause 406.2.2 - Grading Requirement
MORTH Clause 406.3.5 - Compaction

Related Resources on InfraLens

Cross-Referenced Codes
IS 2386:1963Methods of Test for Aggregates for Concrete -...
→

Frequently Asked Questions4

What is the required compaction for a WMM layer?+
The compacted density must be at least 98% of the Maximum Dry Density (MDD) determined by heavy compaction test IS 2720 (Part 8).
What is the maximum allowed Los Angeles Abrasion value for WMM aggregates?+
The LA Abrasion value should not exceed 40% as per Table 400-12 of MORTH specifications.
What are the plasticity requirements for the fine material in WMM?+
The material passing the 425-micron sieve must have a Plasticity Index (PI) of not more than 6.
What is the maximum thickness of a single compacted WMM layer?+
A single compacted layer thickness should not exceed 250 mm and is typically laid in 100mm or 200mm layers.

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