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IS 9142:1979 Part 1 is the Indian Standard (BIS) for lightweight aggregates for structural concrete - part 1: manufactured aggregates. This code of practice provides guidelines for the use of lightweight aggregates in structural concrete. It outlines the classification, properties, and testing of these aggregates, and details the mix design, properties, and special design considerations for lightweight concrete, such as modifications to the modulus of elasticity and shear strength calculations.
Specifies requirements for manufactured lightweight aggregates suitable for use in structural concrete.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Lightweight aggregates have high water absorption; pre-wetting them before mixing is essential to control workability and the effective water-cement ratio.
! Due to the lower density of aggregates, lightweight concrete is more prone to segregation. Careful handling, placing, and controlled vibration are crucial.
! Structural design must account for the lower modulus of elasticity, tensile strength, and shear strength compared to normal weight concrete of the same compressive strength, using the modification factors provided in this code.
Standard Specification for Lightweight Aggregates for Structural Concrete
Specifies requirements for lightweight aggregates intended for use in structural concrete.
EN 13055:2016CEN (European Committee for Standardization), Europe
HighCurrent
Lightweight aggregates
Covers lightweight aggregates for concrete, mortar, and grout, sharing the core application.
JIS A 5002:2015JSA (Japanese Standards Association), Japan
HighCurrent
Lightweight aggregates for structural concrete
Defines quality requirements for artificial lightweight aggregates used in structural concrete.
BS 3797:1990BSI (British Standards Institution), UK
MediumWithdrawn
Specification for lightweight aggregates for masonry units and structural concrete
The historical British equivalent before the adoption of the harmonized European standard.
Key Differences
≠IS 9142 uses the 'Aggregate Crushing Value' (ACV) test to assess aggregate strength, whereas ASTM C330 requires testing the compressive strength of a concrete mix made with the aggregate.
≠ASTM C330 includes a mandatory limit for the drying shrinkage of concrete made with the lightweight aggregate (≤ 0.07%), a performance requirement not specified in IS 9142.
≠IS 9142 specifies maximum bulk densities for fine and coarse aggregates, while EN 13055 uses a system of density classes, providing more flexibility for different applications.
≠The limit for Loss on Ignition (LOI) in IS 9142 (≤ 6%) is slightly more lenient than in ASTM C330 (≤ 5%), reflecting different tolerances for unburnt carbon content.
Key Similarities
≈All standards divide lightweight aggregates into fine and coarse fractions, typically using a 4 mm or 5 mm sieve as the separation point.
≈IS 9142, ASTM C330, and EN 13055 all specify requirements and test methods for grading (sieve analysis) to ensure proper particle size distribution for concrete production.
≈All standards aim to control deleterious materials and include a soundness test (typically using sodium or magnesium sulphate) to ensure the aggregate's durability against weathering.
≈The fundamental purpose of all compared standards is to qualify manufactured lightweight aggregates for use in producing structural-grade concrete with reduced density.
Parameter Comparison
Parameter
IS Value
International
Source
Loose Bulk Density (Coarse Aggregate)
≤ 1000 kg/m³
≤ 880 kg/m³ (55 lb/ft³)
ASTM C330/C330M-22
Loose Bulk Density (Fine Aggregate)
≤ 1200 kg/m³
≤ 1120 kg/m³ (70 lb/ft³)
ASTM C330/C330M-22
Aggregate Crushing Value (ACV)
≤ 45%
Not specified; strength is measured via concrete cylinder test (min 17.2 MPa).
ASTM C330/C330M-22
Water Absorption (24 hr)
≤ 25% by mass
No specific limit; the value must be determined and reported to the purchaser.
ASTM C330/C330M-22
Loss on Ignition
≤ 6%
≤ 5.0%
ASTM C330/C330M-22
Soundness Loss (5 cycles, Magnesium Sulphate)
≤ 15%
≤ 16%
ASTM C330/C330M-22
Resistance to Crushing
Specified as Aggregate Crushing Value ≤ 45%
Reported as a resistance category (e.g., LA15, LA20). No single mandatory limit.
EN 13055:2016
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
Oven-Dry Density Range of Structural Lightweight Concrete1440 to 1840 kg/m³
Shear Strength Modification Factor (λ) for all-lightweight concrete0.80
Shear Strength Modification Factor (λ) for sand-lightweight concrete0.85
Typical Water Absorption of Lightweight Aggregates5 to 25 percent by weight
Minimum Cement Content for Moderate Exposure300 kg/m³
Maximum Free Water-Cement Ratio for M20 Concrete0.55
Key Formulas
Ec = w^1.5 * 0.043 * sqrt(fck) — Modulus of Elasticity for lightweight concrete
How is the Modulus of Elasticity (Ec) of lightweight concrete calculated?+
It's calculated using the formula Ec = w^1.5 * 0.043 * sqrt(fck), where 'w' is the oven-dry density in kg/m³ and 'fck' is the characteristic strength (Clause 5.2.1).
Do I use the same shear strength values for lightweight concrete as for normal concrete in IS 456?+
No. The design shear strength (τc) from IS 456 must be multiplied by a modification factor 'λ' (e.g., 0.80 for all-lightweight concrete) as per Clause 8.2.1.
What is the primary advantage of using structural lightweight concrete?+
The main advantage is the reduction in the dead load of the structure, which can lead to smaller foundations, longer spans, and improved seismic performance.
What is meant by 'pre-wetting' lightweight aggregates?+
It is the process of adding water to the aggregates before mixing them into the concrete to satisfy their high water absorption, preventing them from drawing water from the mix. (Clause 9.1.2)