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IS 4122:1967 is the Indian Standard (BIS) for method of test for surface softening of natural building stones by exposure to acidic atmospheres. This standard prescribes the method of test for determining the susceptibility of natural building stones to surface softening when exposed to acidic atmospheres, simulating industrial or highly polluted environments.
Method of test for surface softening of natural building stones by exposure to acidic atmospheres
EN 13919:2002CEN (European Committee for Standardization), Europe
MediumCurrent
Natural stone test methods - Determination of the resistance to ageing by SO2 action in the presence of humidity
Both assess stone durability against acidic pollutants, but IS 4122 uses liquid acid immersion while EN 13919 uses SO2 gas exposure.
ASTM C217 - 18ASTM International, USA
HighCurrent
Standard Test Method for Weather Resistance of Slate
Both use a sulfuric acid immersion test, though IS 4122 applies to all building stones and ASTM C217 is specific to slate.
Key Differences
≠Test Method: IS 4122 uses direct immersion in a liquid sulfuric acid solution, which is a simpler but more aggressive test. In contrast, EN 13919 uses a controlled atmosphere with sulfur dioxide (SO2) gas and high humidity, which more accurately simulates real-world acid rain conditions.
≠Primary Assessment Criteria: The main result from IS 4122 is quantitative, based on the percentage loss of mass. International standards like ASTM C217 focus on qualitative and semi-quantitative results, such as the depth of softening measured with a scraper and visual changes (crumbling, flaking).
≠Test Duration and Cycles: IS 4122 specifies a continuous 4-day immersion. ASTM C217 requires a 7-day immersion, while EN 13919 is a cyclic test involving 21 cycles of exposure to the SO2 atmosphere.
≠Material Scope: IS 4122 is a general method for all 'natural building stones'. ASTM C217 is specifically tailored for slate, which has a distinct mineralogy and fabric (foliation) that influences its reaction to acid.
Key Similarities
≈Core Objective: Both the Indian standard and the international equivalents share the fundamental purpose of evaluating the durability of natural stone by simulating the deteriorating effects of acidic atmospheric pollution.
≈Use of Sulfuric Agent: Both IS 4122 and ASTM C217 use sulfuric acid (H2SO4) as the aggressive chemical. EN 13919 uses SO2 gas, which is the atmospheric precursor to sulfuric acid, thus targeting the same chemical attack mechanism.
≈Specimen Conditioning: All standards require the test specimens to be dried to a constant mass in an oven before testing to establish a consistent and dry baseline for weight and condition.
≈Qualitative Observation: Alongside quantitative measurements, all methods include a requirement for visual examination of the specimens after exposure to note any physical degradation such as crumbling of edges, formation of powder, or significant changes in texture and appearance.
Parameter Comparison
Parameter
IS Value
International
Source
Test Agent
1% solution of sulfuric acid (H2SO4)
1% solution of sulfuric acid (H2SO4)
ASTM C217 - 18
Test Agent (Alternative Method)
Liquid H2SO4 solution
Sulphur dioxide (SO2) gas and water vapour
EN 13919:2002
Test Duration
4 days (96 hours)
7 days
ASTM C217 - 18
Test Duration (Cyclic)
4 days continuous
21 cycles of 24 hours each
EN 13919:2002
Primary Evaluation Metric
Percentage loss in weight
Depth of softening and visual changes
ASTM C217 - 18
Primary Evaluation Metric (Alternative)
Percentage loss in weight
Change in mass and visual evaluation score
EN 13919:2002
Specimen Shape
50 mm cube
50 x 50 mm, thickness as quarried (for slate)
ASTM C217 - 18
Pre-Test Drying Temperature
105 ± 5 °C until constant weight
70 ± 5 °C until constant weight
EN 13919:2002
⚠ Verify details from original standards before use
Key Values3
Quick Reference Values
weighing accuracy0.001 g
specimen sizeTypically 50 mm x 50 mm cubes or cylinders
exposure agentSulphur dioxide (SO2) or equivalent acidic solution
Key Formulas
Surface Softening (g/cm²) = (W1 - W2) / A — where W1 is initial weight, W2 is weight after scraping, and A is scraped area
Tables & Referenced Sections
Key Tables
No tables data
Key Clauses
Clause 2 - Apparatus
Clause 3 - Test Specimen preparation
Clause 4 - Procedure for exposure to acidic atmosphere
Stones used for exterior facing and cladding, particularly in industrial or heavily polluted atmospheres, such as limestone, marble, and certain calcareous sandstones.
How is the surface softening quantitatively measured?+
By scraping the exposed surface of the stone with a standardized scraping apparatus under a constant load and measuring the loss in weight.
Why is exposure to acidic atmospheres a concern for building stones?+
Pollutants like sulfur dioxide react with moisture to form acids, which chemically attack the calcium carbonate in stones, leading to surface degradation, softening, and eventually structural or aesthetic failure.