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IS 6041:1985 is the Indian Standard (BIS) for construction of autoclaved cellular concrete block masonry. This code provides guidelines for the construction of masonry using autoclaved cellular concrete (AAC) blocks. It covers the specifications for materials like blocks and mortar, and details the workmanship including block laying, jointing, and curing to ensure quality construction.
Code of practice for construction of autoclaved cellular concrete block masonry
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Unlike clay bricks, AAC blocks should not be soaked for long periods. A quick dip in water just before laying is sufficient to prevent rapid water absorption from the mortar.
! AAC blocks are relatively brittle and can chip easily; careful handling is required on-site to minimize wastage and ensure clean edges for proper jointing.
! While this code specifies traditional cement-sand mortar, modern practice often involves using pre-mixed thin-bed block jointing mortar for better adhesion, faster construction, and improved thermal performance.
EN 1996-2:2006CEN (European Committee for Standardization), Europe
HighCurrent
Eurocode 6: Design of masonry structures - Part 2: Design considerations, selection of materials and execution of masonry
Covers material selection, workmanship, and execution of masonry, which directly parallels the 'code of practice' scope of IS 6041.
AS 3700-2018Standards Australia, Australia
HighCurrent
Masonry structures
A comprehensive standard covering design and construction practices for various masonry types, including AAC (cellular concrete).
ACI 530.1/ASCE 6/TMS 602-13ACI/ASCE/TMS, USA
MediumCurrent
Specification for Masonry Structures
Specifies minimum requirements for masonry construction, including materials and workmanship, but is part of a larger set of codes.
BS 5628-3:2005BSI (British Standards Institution), UK
HighWithdrawn
Code of practice for the use of masonry - Part 3: Materials and components, design and workmanship
A historical equivalent with a very similar scope, covering materials and workmanship for masonry construction in the UK.
Key Differences
≠IS 6041 is highly prescriptive, specifying exact mortar mix ratios (e.g., 1:6 cement:sand). Modern standards like Eurocode 6 are performance-based, specifying mortar by strength class (e.g., Class M5) rather than by recipe.
≠The Indian standard requires blocks to be 'soaked' in water before use. Modern international practice, guided by standards like EN 1996-2, advises against soaking and recommends only light wetting to achieve a Saturated Surface Dry (SSD) condition to prevent excessive shrinkage and poor bond.
≠IS 6041 is a standalone code for construction practice. International standards like Eurocode 6 and AS 3700 are integrated systems where the execution/workmanship standard (e.g., EN 1996-2) is directly linked to the design standard (e.g., EN 1996-1-1).
≠While IS 6041 mentions thin-bed mortars, it treats them as an alternative. Modern codes and practices strongly favor thin-bed mortars for dimensionally accurate AAC blocks to maximize thermal efficiency and construction speed.
Key Similarities
≈All standards emphasize the need for proper workmanship, including maintaining level courses, ensuring walls are plumb, and using a consistent, full mortar bed (for traditional mortar).
≈Both IS 6041 and international counterparts like EN 1996-1-1 provide similar limitations on chasing and cutting, for instance, limiting the depth of vertical chases to a fraction (e.g., 1/3) of the wall's thickness.
≈The principle of curing masonry to ensure proper hydration and strength gain of the mortar is common to both the Indian standard (specifying 7 days of water sprinkling) and international practices.
≈All standards require the use of a running (stretcher) bond for unreinforced walls, specifying a minimum lap of a quarter of the block length or a fixed dimension to ensure structural integrity.
Parameter Comparison
Parameter
IS Value
International
Source
Mortar Type Specification
Prescriptive mix ratio, e.g., 1:6 cement:sand for walls.
Performance-based strength class, e.g., General purpose mortar Class M4 or M5.
EN 1996-2:2006
General Purpose Mortar Joint Thickness
10 to 12 mm
Target thickness of 10 mm (range 8-15 mm is acceptable).
EN 1996-2:2006
Thin Layer Mortar Joint Thickness
About 3 mm
0.5 mm to 3 mm
EN 1996-2:2006
Pre-wetting of Blocks
Blocks shall be soaked in water before use.
Wetting is required to control suction but soaking is not recommended; a light spray or quick dip to achieve SSD is preferred.
General AAC construction practice aligned with ASTM/EN
Curing Period
Sprinkling with water for at least 7 days.
Masonry shall be protected from drying too rapidly for at least 48 hours after construction.
ACI 530.1-13
Max. Depth of Vertical Chase (unreinforced wall)
1/3 of the thickness of masonry.
≤ 1/3 of the wall thickness.
EN 1996-1-1:2005
Scaffolding Support
No part of the scaffolding should be supported on the wall under construction.
Scaffolding shall be designed to not impart lateral loads onto the wall, unless the wall is designed for such loads.
AS 3700-2018
⚠ Verify details from original standards before use
Key Values4
Quick Reference Values
General purpose cement-sand mortar ratio (by volume)1:6
Maximum mortar joint thickness15 mm
Minimum curing period for masonry7 days
Maximum height of masonry to be built at a time1 m