Simplified Guide to Petrographic Examination of Aggregates (IS 2386 Part VIII - 1963)

 IS.2386.8.1963

Simplified Guide to Petrographic Examination of Aggregates (IS 2386 Part VIII - 1963)

The standard describes two methods for petrographic examination:

1. Method I: A routine visual and basic microscopic examination for quick assessment.
2. Method II: A detailed petrographic analysis for in-depth investigation, serving as the reference method.

These methods help identify the suitability of aggregates for concrete by evaluating their mineral composition, physical properties, and potential for deleterious reactions, such as alkali-aggregate reactivity.

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Why Perform Petrographic Examination?

Petrographic examination identifies the mineralogical and physical characteristics of aggregates, which affect the strength, durability, and stability of concrete. It detects potentially deleterious constituents (e.g., opal, chert, or clay minerals) that could cause issues like alkali-silica reaction (ASR) or poor mechanical performance in concrete structures.

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1. Method I: Routine Petrographic Examination

Purpose

To perform a quick visual and basic microscopic examination to segregate and identify aggregate constituents based on petrographic, physical, and chemical differences.

Apparatus

• Screens: IS sieves (150 µm, 300 µm, 600 µm, 1.00 mm, 2.5 mm, 4.75 mm, 10 mm, 12.5 mm, 20 mm, 25 mm, 40 mm, 50 mm, 80 mm).
• Balance: 2 kg capacity, sensitive to 0.1 g.
• Anvil and Hammer: For breaking pebbles, with a tray to minimize loss of rock chips.
• Hand Lens and Microscopes: Stereoscopic and petrographic microscopes for visual and mineralogical identification.
• Auxiliary Equipment: For chemical tests (e.g., acid tests) and sample preparation.

Procedure

1. Sample Preparation (Clause 2.3):
   • Screen aggregates to obtain specified quantities for each size fraction:
     • 80 mm: 4000 g
     • 40 mm: 1000 g
     • 20 mm: 200 g
     • 10 mm: 100 g
     • 4.75 mm and smaller: 25–50 g
   • Dry samples in an oven at 105–110°C to remove moisture.
2. Examination (Clauses 2.3–2.4):
   • Examine each size fraction separately using a hand lens or stereoscopic microscope.
   • Check for coatings (e.g., opal, calcium carbonate, gypsum, clay, or organic matter) and assess their bonding strength and potential impact on concrete durability.
   • Break coarse aggregate particles using an anvil and hammer to expose fresh surfaces.
   • Identify particles by:
     • Petrographic Identity: Rock type (e.g., granite, limestone, sandstone).
     • Physical Condition: Good, satisfactory, fair, or poor (based on strength, durability, and abrasion resistance).
     • Chemical Stability: Non-reactive or deleterious (e.g., opal, chalcedony, tridymite, cristobalite) in concrete.
   • Use chemical tests (e.g., acid tests) or immersion oils under a petrographic microscope to confirm mineral identity if needed.
3. Reporting (Clause 2.4):
   • Summarize findings in a report detailing:
     • Petrographic identity, proportion, and characteristics of each constituent.
     • Physical and chemical quality ratings (see Clause 2.4 for quality scale).
     • Suitability for concrete under anticipated service conditions.
     • Recommendations for additional tests (e.g., alkali-aggregate reactivity tests per IS 2386 Part VII) if deleterious substances are detected.

Example

A coarse aggregate sample is examined:

• Sample: River gravel, sieved to 20 mm fraction (200 g).
• Examination: 60% granite (good physical quality, non-reactive), 30% limestone (satisfactory, non-reactive), 10% chert (fair, potentially reactive due to opal content).
• Coatings: Some limestone particles have clay coatings, removable by washing.
• Report: Granite and limestone are suitable; chert requires further testing (e.g., mortar-bar test) due to potential alkali-silica reactivity.

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2. Method II: Detailed Petrographic Examination

Purpose

To conduct a comprehensive petrographic analysis for precise identification of aggregate constituents, their physical and chemical properties, and their suitability for concrete.

Apparatus and Supplies

• Sample Preparation (Clause 3.1.1):
  • Rock-cutting saw (350 mm diamond blade).
  • Horizontal grinding wheel (400 mm) and polishing wheel (200–300 mm).
  • Abrasives (silicon carbide grit, emery).
  • Microscope slides (25 x 45 mm), Canada balsam, xylene, mounting medium.
  • Laboratory oven, Jones riffle sampler, Plattner mortar.
• Examination (Clause 3.2.2):
  • Polarizing microscope with mechanical stage, low/medium/high-power objectives, compensators, and immersion media (refractive index 1.400–1.785).
  • Stereoscopic microscope (6X–60X magnification).
  • Magnet, needle holder, dropping bottle, Petri dishes, lens paper.
  • Photomicrographic camera for documentation.

Procedure

1. Sampling (Clause 3.3):
   • Quarries: Collect ≥2.5 kg from each stratum, with no piece <0.5 kg, or use drilled cores.
   • Sand and Gravel Deposits: Sample via test pits to anticipated production depth, with quantities based on sieve size.
   • Ensure samples are representative of the deposit.
2. Examination of Natural Gravel (Clause 3.4.2):
   • Sort pebbles by rock type using visual inspection, stereoscopic microscope, or acid/scratch tests.
   • Check for deleterious coatings (e.g., opal, gypsum, soluble salts).
   • Assess physical condition (e.g., fracturing, porosity) and chemical stability (e.g., presence of reactive silica minerals).
   • Examine at least 300 particles per sieve fraction for reliable statistical results.
3. Examination of Natural Sand (Clause 3.4.3):
   • For sizes >600 µm, reduce samples using a Jones riffle sampler to obtain ≥300 particles per fraction.
   • Examine under a stereoscopic microscope, submerging grains in water to reduce reflection and aid identification.
   • Use petrographic microscope for fine-grained or suspect particles (e.g., those containing opal or chalcedony).
   • Record particle shape, surface texture, grain size, mineral composition, and presence of deleterious substances.
4. Examination of Crushed Stone (Clause 3.5.3):
   • Follow similar procedures as for gravel, focusing on particle counts per sieve fraction.
   • Assess fracturing caused by crushing, which may affect durability.
5. Additional Test for Undulatory Extinction (UE) (Clause 3.7, Amendment No. 1, June 1999):
   • For aggregates with >30% quartz, measure the undulatory extinction angle using a polarizing microscope in transmitted light.
   • Record the angle between the first and second extinction positions of quartz grains.
   • Average UE angles across grains in a thin section.
   • Determine the percentage of quartz grains showing UE via point-counting.
   • Note: UE indicates crystal lattice distortion, which may correlate with alkali reactivity (e.g., strained quartz).
6. Calculations and Reporting (Clause 3.6):
   • Calculate the weighted percentage of each constituent in each sieve fraction (Clause 3.6.1.3).
   • Sum weighted percentages to obtain the overall composition (Clause 3.6.1.4).
   • Construct tables (e.g., Table III and IV) showing composition and condition by sieve fraction and for the whole sample.
   • Report trace constituents (≤0.5%) separately.
   • Prepare a summary report (brief, for engineers) and a detailed report (including test procedures, data, tables, and photographs).
   • Describe deleterious properties quantitatively and their potential effects on concrete (e.g., cracking due to reactive minerals).

Example

A crushed stone sample is analyzed:

• Sample: Quarry aggregate, sieved to 10 mm fraction (100 g).
• Examination: 50% quartzite (UE angle 20°, 40% quartz with UE), 30% granite, 15% sandstone, 5% chert (potentially reactive).
• Calculations: Weighted composition shows 2% chert in the whole sample.
• Report: Quartzite’s high UE suggests potential reactivity; recommend alkali-aggregate reactivity testing (IS 2386 Part VII). Granite and sandstone are suitable.

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Key Tips for Students and Engineers

• Method I:
  • Ideal for quick assessments when time or resources are limited.
  • Focus on identifying coatings and reactive minerals (e.g., opal, chert).
  • Use simple tools (hand lens, stereoscopic microscope) for cost-effective analysis.
• Method II:
  • Requires specialized equipment (e.g., polarizing microscope, thin-section preparation tools).
  • Essential for critical projects (e.g., dams, bridges) where aggregate quality is paramount.
  • Ensure precise calibration of immersion media refractive indices for accurate mineral identification.
• General:
  • Examine at least 300 particles per sieve fraction for statistical reliability.
  • Cross-reference findings with IS 2386 Part VII (Alkali Aggregate Reactivity) for suspect aggregates.
  • Document observations thoroughly, as reports guide engineering decisions.

Common Mistakes to Avoid

• Method I:
  • Overlooking minor coatings that may affect concrete bonding.
  • Inadequate particle breaking, missing internal defects.
• Method II:
  • Insufficient particle counts (<300), leading to unreliable composition estimates.
  • Poor thin-section preparation, affecting microscopic analysis.
  • Neglecting temperature control for immersion media, causing inaccurate refractive index measurements.
• Document Issues:
  • Typographical errors: “2366”, “2866”, “2966” instead of “2386”; “AGREGATES” instead of “AGGREGATES”; “Petorgraphic” instead of “Petrographic”.
  • Truncated text limits procedural details; consult the full standard for clarity.
  • Amendment No. 1 (1999) adds UE testing but lacks detailed procedural steps in the provided excerpt.

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Notes on Document Issues

• Typographical Errors: References to “2366”, “2866”, “2966”, or “2.86” are typos for “2386”. “AGREGATES” is a typo for “AGGREGATES” (Pages 5, 7, 13, 26). “Petorgraphic” is a typo for “Petrographic” (Page 12).
• Truncation: Large sections are missing, limiting details on procedures, calculations, and table formats (e.g., Tables I–IV).
• Amendment: Amendment No. 1 (June 1999) adds undulatory extinction testing for quartz-rich aggregates (>30% quartz) to assess alkali reactivity potential.
• Reference Standards:
  • IS 2:1960 (Rules for Rounding Off Numerical Values).
  • IS 2386 Part I (Particle Size and Shape).
• Year: Adopted in 1963, reaffirmed in 2002, with Amendment No. 1 in 1999.

For complete details, refer to the full IS 2386 (Part VIII) - 1963 document, including Amendment No. 1.

 

Simplified Guide to Testing Alkali Aggregate Reactivity (IS 2386 Part VII - 1963)

 IS.2386.7.1963

Simplified Guide to Testing Alkali Aggregate Reactivity (IS 2386 Part VII - 1963)

The standard covers two methods to evaluate the potential alkali-aggregate reactivity of fine and coarse aggregates used in concrete:

1. Mortar-Bar Method: Measures expansion in mortar bars to assess physical reactivity.
2. Chemical Method: Analyzes chemical interactions between aggregates and sodium hydroxide to determine potential reactivity.

These tests are critical to prevent alkali-silica reaction (ASR) or alkali-carbonate reaction (ACR), which can cause concrete deterioration due to expansive gel formation.

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Why Test Alkali Aggregate Reactivity?

Alkali-aggregate reactions occur when alkalis (e.g., sodium or potassium oxides) from cement react with certain minerals in aggregates, forming gels that expand in the presence of moisture. This can lead to cracking, reduced durability, and structural failure in concrete. The tests ensure aggregates are safe for use in concrete structures like dams, bridges, and buildings.

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1. Mortar-Bar Method

Purpose

To measure the expansion of mortar bars made with the test aggregate to determine if it causes deleterious alkali-aggregate reactions.

Apparatus

• Scales and Weights: Scales with a permissible variation of ±2.0 g at 2000 g load (new scales: ±1.0 g). Weights as per Table 1 (e.g., ±1 g for 100 g weight).
• Sieves: Square-hole, woven wire cloth sieves per IS 460:1962 (e.g., 850-micron, 300-micron, 150-micron).
• Glass Graduates: 200 ml capacity, calibrated at 20°C with ±0.5 ml deviation.
• Moulds: Single or double moulds for 25 x 25 mm specimens, with gauge studs (6.5 mm diameter) penetrating 15.0–18.5 mm. Moulds must be rigid, made of steel or brass.
• Mixing Bowl: As shown in Fig. 3.
• Comparator: For precise length measurements (Fig. 4), calibrated with a reference bar.
• Moist Closet/Room: Maintains 27 ± 2°C and ≥90% relative humidity.
• Storage Room: Maintains 30 ± 2°C for specimen storage.
• Measuring Device: Dial gauge or micrometer, calibrated regularly, with a range of ≥7.5 mm.

Materials

• Cement: Low-alkali Portland cement (≤0.1% sodium oxide by weight). Pass through an 850-micron sieve to remove lumps.
• Aggregate:
  • Fine aggregate: Processed with minimal crushing.
  • Coarse aggregate: Crushed to produce a graded product (per clause 2.4.2).
  • Both must be representative of the material proposed for use.
• Water: Distilled or equivalent purity.

Procedure

1. Aggregate Preparation:
   • Fine aggregate: Process with minimal crushing.
   • Coarse aggregate: Crush to achieve grading as per clause 2.4.2.
   • Sieve to ensure proper particle size (e.g., 300–150 micron for chemical method).
2. Mortar Mixing (Clause 2.5.4):
   • Sequence: Add water to the bowl, mix cement for 30 seconds, add half the aggregate and mix for 30 seconds, then add the remaining aggregate and mix for 14 minutes.
3. Moulding Test Specimens (Clause 2.5.5):
   • Fill moulds immediately after mixing, using compressed air to level the top.
   • Compact mortar around gauge studs and mould surfaces.
   • Smooth the surface with a trowel after compaction.
   • Place moulds in a moist closet (27 ± 2°C, ≥90% humidity) for 24 ± 2 hours.
4. Storage and Measurement (Clause 2.6):
   • After 24 ± 2 hours, demould specimens, measure initial length, and store in a moist room (23 ± 2°C) for 28 days.
   • Measure length again at 28 days and calculate the change.
   • For longer-term tests, measure at 1, 2, 3, 6, 9, and 12 months, and every 6 months thereafter.
   • Store specimens in a container over (but not in contact with) water at 35 ± 2°C. Before measuring, cool to 21 ± 2°C for at least 1 hour.
5. Examination (Clause 2.8.2):
   • Inspect for cracking patterns, surface mottling, and other notable conditions.
   • Conduct petrographic analysis if gel-filled pores or reactive aggregate particles are suspected.
6. Calculation (Clause 2.7):
   • Calculate length change as a percentage to the nearest 0.001%: $$\text{Length Change (\%)} = \frac{\text{Length at time t} - \text{Initial Length}}{\text{Initial Length}} \times 100$$
   • Measure curvature by placing the specimen on a flat surface and measuring the gap to the nearest 0.2 mm.

Reporting Results (Clause 2.9)

• Aggregate type and source.
• Cement type, source, and alkali content (% Na₂O, K₂O, and Na₂O equivalent).
• Average length change (%) at each measurement.
• Grading details if different from clause 2.4.2.
• Mixing water percentage by cement weight.
• Observations from specimen examination (e.g., cracking, gel presence).
• Repeatability: Expansion should not differ by more than 0.05% from the batch average.

Amendments

• Amendment No. 1 (June 1999) (Clause 2.11):
  • For aggregates with >30% strained quartz (undulatory extinction angle >15°), conduct additional tests in a metal container with sodium hydroxide solution to assess microcrystalline quartz reactivity.
• Amendment No. 2 (June 2009):
  • Table 1: Corrects permissible variation for 1000 g weight to ±1.8 g (from ±1.0 g).
  • Clause 2.5.3: Specifies “ten 12.5-mm drops” for the flow test.

Example

A river sand is tested:

• Mix: Cement with 0.1% Na₂O, sand graded per clause 2.4.2, water.
• Moulding: Prepare 25 x 25 mm bars, cure for 24 hours at 27°C, then store at 23°C for 28 days.
• Measurement: Initial length = 250.00 mm; after 28 days = 250.25 mm.
• Calculation: Length change = $(250.25 - 250.00) / 250.00 \times 100 = 0.1$.
• Interpretation: If expansion >0.1% at 6 months (per typical limits), the aggregate may be reactive, requiring further petrographic analysis.

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2. Chemical Method

Purpose

To assess the potential reactivity of aggregates by measuring dissolved silica and reduction in alkalinity when reacted with sodium hydroxide solution.

Apparatus

• Scales and Balances:
  • Scales: ±2.0 g variation at 2000 g (new: ±1.0 g).
  • Analytical balance: ≥100 g capacity, ±0.0002 g reproducibility, ±0.0005 g stability.
• Sieves: 300-micron and 150-micron IS sieves.
• Containers: 250 ml polyethylene containers.
• Reagents:
  • Distilled water.
  • Ammonium molybdate solution (10 g in 100 ml water).
  • Hydrochloric acid (concentrated, sp gr 1.19; 0.05 N; 1:1 dilution).
  • Hydrofluoric acid.
  • Oxalic acid solution (10 g dihydrate in 100 ml water).
  • Phenolphthalein indicator (1 g in 100 ml ethanol).
  • Standard silica solution (10 millimoles SiO₂/litre).
  • Standard sodium hydroxide solution (1.000–1.010 N).
  • Concentrated sulphuric acid (sp gr 1.84).

Procedure

1. Sample Preparation (Clause 3.5.3):
   • Crush aggregate and sieve to obtain material passing 300-micron and retained on 150-micron IS sieve.
   • Wash over 150-micron sieve to remove fines, dry at 100–105°C for 20–24 hours, and re-sieve.
   • Repeat washing if silty or clayey coatings persist.
2. Reaction Procedure (Clause 3.6):
   • Weigh three 25.00 ± 0.05 g portions of the prepared aggregate.
   • Place each in a 250 ml polyethylene container with 25 ml of 1.000 N NaOH solution.
   • Add 50 ml NaOH to a fourth container (blank).
   • Cure at 80°C for 24 hours, then filter the liquid.
   • Dilute filtrate to 200 ml in a volumetric flask for analysis.
3. Dissolved Silica (Gravimetric Method) (Clause 3.7):
   • Take 100 ml of diluted solution, evaporate with 5–10 ml hydrochloric acid (sp gr 1.19) on a steam bath.
   • Repeat evaporation to remove residual acid.
   • Heat residue, dissolve in hydrochloric acid, and filter to collect silica.
   • Calculate silica concentration: $$S_1 = (W_1 - W_2) \times 3.330$$ where $S_1$ is silica concentration (millimoles/litre), $W_1$ is silica weight in 100 ml sample, and $W_2$ is silica in the blank.
4. Dissolved Silica (Photometric Method) (Clause 3.8):
   • Use for rapid analysis of crystalloidal silica, avoiding interference from tannins.
   • Follow specific photometric procedures (not detailed in the provided excerpt).
5. Reduction in Alkalinity (Clause 3.9):
   • Titrate filtrate with 0.05 N hydrochloric acid to phenolphthalein endpoint ($P$).
   • Optionally, titrate to methyl orange endpoint ($T$) and calculate: $$R_1 = 2P - T$$ where $R_1$ is the reduction in alkalinity.

Reporting Results

• Aggregate type and source.
• Dissolved silica concentration (millimoles/litre).
• Reduction in alkalinity.
• Any deviations from standard grading or procedure.
• Chemical analysis of reagents used.

Interpretation (Clause 3.10)

• Compare results with established data on aggregate performance in structures or mortar-bar tests.
• High silica dissolution (>100 millimoles/litre) or significant alkalinity reduction may indicate potential reactivity.
• Confirm with petrographic examination or mortar-bar test results.

Example

A quarry aggregate is tested:

• Sample: 25 g (300–150 micron) reacted with 25 ml 1 N NaOH at 80°C.
• Silica Analysis: 100 ml filtrate yields 0.03 g silica; blank yields 0.001 g.
• Calculation: $S_1 = (0.03 - 0.001) \times 3.330 = 96.57$ millimoles/litre.
• Alkalinity: Titration shows significant reduction.
• Interpretation: High silica dissolution suggests potential reactivity, requiring mortar-bar testing for confirmation.

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Key Tips for Students and Engineers

• Mortar-Bar Method:
  • Ensure precise length measurements (±0.001%) using a calibrated comparator.
  • Maintain strict temperature (27 ± 2°C) and humidity (≥90%) conditions to avoid variability.
  • Use low-alkali cement to isolate aggregate reactivity.
• Chemical Method:
  • Handle reagents (e.g., hydrofluoric acid) with care due to their hazardous nature.
  • Ensure thorough washing to remove fines, as they can skew silica measurements.
  • Standardize NaOH and HCl solutions daily for accurate titration.
• General:
  • Cross-check results with petrographic analysis for aggregates with suspected reactive minerals (e.g., opal, chalcedony).
  • Refer to Amendments No. 1 and 2 for updated procedures and tolerances.

Common Mistakes to Avoid

• Mortar-Bar:
  • Inconsistent mould filling or compaction, leading to variable expansion.
  • Incorrect storage conditions (e.g., temperature deviations).
  • Neglecting regular comparator calibration.
• Chemical Method:
  • Incomplete removal of fines, affecting silica dissolution results.
  • Using outdated or contaminated reagents.
  • Improper filtration, leading to inaccurate silica or alkalinity measurements.
• Document Errors:
  • The standard is inconsistently labeled (e.g., “2366” or “2396” instead of “2386”).
  • “AGREGATES” is a typo for “AGGREGATES” (Page 7, 29).
  • Truncated text limits procedural details; consult the full standard for clarity.

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Notes on Document Issues

• Typographical Errors: References to “2366”, “2396”, or “2.96” are typos for “2386”. “AGREGATES” should be “AGGREGATES”.
• Truncation: Large sections are truncated, omitting critical details (e.g., full procedures for photometric analysis, grading specifics in clause 2.4.2).
• Amendments:
  • Amendment No. 1 (1999): Adds testing for aggregates with strained quartz.
  • Amendment No. 2 (2009): Corrects weight tolerances and flow test details.
• Reference Standards:
  • IS 460:1962 (Test Sieves).
  • IS 1727:1960 (Pozzolanic Materials Testing).
  • IS 2:1960 (Rounding Off Numerical Values).
• Year Discrepancy: The standard is from 1963, reaffirmed in 2002, with amendments in 1999 and 2009.

For complete details, refer to the full IS 2386 (Part VII) - 1963 document, including Amendments No. 1 and 2.

Simplified Guide to Measuring Mortar Making Properties of Fine Aggregate (IS 2386 Part VI - 1963)

 IS.2386.6.1963

Simplified Guide to Measuring Mortar Making Properties of Fine Aggregate (IS 2386 Part VI - 1963)

The test described in IS 2386 (Part VI) - 1963 evaluates the compressive strength of fine aggregates in concrete by creating mortar specimens and testing their performance under compression. This is crucial for assessing how fine aggregates contribute to the quality and strength of concrete in structures like buildings, bridges, and pavements.

Why Test Mortar Making Properties?

Fine aggregates (sand) significantly affect the workability, strength, and durability of concrete. This test measures how well a fine aggregate performs in a mortar mix, ensuring it meets the requirements for producing strong and durable concrete. It is particularly important when the quality of the aggregate is uncertain or when comparing different sources of sand.

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Test Overview

What It Measures

The test determines the compressive strength of mortar specimens made from fine aggregates, cement, and water at a fixed water-cement ratio (0.6 by weight). The mortar is prepared to a specific flow (workability) and molded into cubes, which are then tested for compressive strength after curing.

Why It Matters

• Ensures fine aggregates produce mortar with adequate strength for concrete applications.
• Helps compare the performance of different fine aggregates, especially when service records are unavailable.
• Identifies aggregates that may negatively impact concrete quality due to poor particle shape, texture, or impurities.

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Apparatus

1. Flow Table and Flow Mould: Conform to IS 1273:1960 (Methods of Test for Pozzolanic Materials).
2. Tamping Bar (per Amendment No. 2, 1991):
   • Made of non-absorbent, abrasion-resistant, non-brittle material (e.g., rubber with Shore A hardness of 35–40 or paraffin-treated teak wood).
   • Minimum length: 25 cm for 50-mm moulds, 20 cm for 75-mm moulds.
   • Tamping face: Flat and at right angles to the bar’s length.
3. Trowel: Steel blade, 100–150 mm long, with straight edges.
4. Tamping Rod: ~10 mm diameter, 100 mm long, with one end rounded to a 10-mm hemispherical tip.
5. Cube Moulds (per Amendment No. 2, 1991):
   • 50-mm cube moulds, conforming to IS 4031:1962 (Specification for Moulds for Cement and Concrete Tests).
   • Note: The document mentions 700 cm cubes, likely a typo for 70-mm or 50-mm cubes, corrected to 50 mm in Amendment No. 2.
6. Compression Testing Machine: Suitable capacity for testing cube specimens.
7. Mixing Vessel and Spoon: For preparing mortar.
8. Moist Closet and Storage Tank: Maintained at 27 ± 2°C for curing.
9. Drying Oven: For drying sand at 105°C for 24 hours.
10. Indicators: Phenolphthalein or litmus to check for sodium hydroxide residue.

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Materials

1. Cement: Standard cement for consistent results.
2. Water: Clean, potable water for mixing and curing.
3. Fine Aggregate:
   • Washed with sodium hydroxide solution (per IS 2386 Part II - 1963, clause 6.2.2) to remove deleterious materials and organic impurities.
   • Ensure no fines are lost during washing.
   • Check for complete removal of sodium hydroxide using phenolphthalein or litmus.
   • Dry at 105°C for 24 hours before use.

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Sample Preparation

1. Fine Aggregate:
   • Wash the sand with sodium hydroxide solution to remove impurities, ensuring no fines are lost.
   • Rinse thoroughly and check with an indicator (e.g., phenolphthalein) to confirm all sodium hydroxide is removed.
   • Dry the sand at 105°C for 24 hours to achieve a dry condition.

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Test Procedure

1. Mortar Preparation:
   • Mix cement and water at a water-cement ratio of 0.6 by weight in a suitable vessel.
   • Allow cement to absorb water for 1 minute, then mix into a smooth paste using a spoon.
   • Add a known weight of dried fine aggregate (3300–5300 g, depending on sand fineness; e.g., 3300 g for fine sand, up to 5300 g for coarse sand).
   • Mix until the mortar achieves a flow of 100 ± 5 (measured per step 2).
   • Continue mixing for 30 seconds after achieving desired consistency.
2. Flow Test:
   • Clean and dry the flow table and place the flow mould at the center.
   • Place a 25-mm layer of mortar in the mould and tamp 20 times with the tamping bar (sufficient pressure to compact).
   • Add a second layer and tamp similarly.
   • Level the mortar surface flush with the mould top using a trowel’s straight edge in a sawing motion.
   • Clean the table, especially around the mould edge.
   • Lift the mould 1 minute after mixing and drop the table 10 times through a 12.5-mm height.
   • Measure the mortar’s diameter along four equally spaced axes and calculate the flow as a percentage of the original diameter.
   • If flow exceeds 100 ± 5, add more sand and repeat. If more than two trials are needed or the mortar is too dry, discard and prepare a new batch.
   • Record the final sand weight by subtracting the remaining portion from the initial sample.
3. Moulding Test Specimens:
   • Immediately after the flow test, place mortar in 50-mm cube moulds in two layers.
   • Rod each layer with 25 strokes of the tamping rod.
   • Fill moulds to overflowing, then strike off to a smooth surface 3–4 hours after moulding.
   • Cure in a moist closet at 27 ± 2°C for 20–24 hours, then demould and store in water at 27 ± 2°C until testing.
4. Testing Specimens:
   • Test cubes for compressive strength after curing:
     • For 2,4-Dichlorophenol specimens: Test immediately after removal from the moist closet.
     • For others: Test 4 days after water storage.
   • Surface-dry each specimen and remove loose sand or incrustations from faces contacting the testing machine’s bearing blocks.
   • If a specimen’s face is significantly curved, grind to a plane surface or discard.
   • Test in a compression testing machine, ensuring plane surfaces for accurate loading.
   • Note: Specimens must be tested quickly after removal from the moist closet to avoid drying, which could affect results.

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Reporting Results

• Flow Value: Report the flow (100 ± 5) achieved during the test.
• Sand Quantity: Report the weight of sand used in the mortar mix.
• Compressive Strength: Report the compressive strength of the cubes (in MPa or N/mm²) after testing.
• Observations: Note any issues (e.g., specimen defects, curing conditions).

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Real-Life Example

For a building project, you test fine aggregate from a local riverbed:

• Mix: Use 1800 g cement, 1080 g water (water-cement ratio = 0.6), and 4000 g dried sand.
• Flow Test: After mixing, the flow is 102, within 100 ± 5. The sand weight used is 3950 g (50 g remains).
• Moulding: Prepare three 50-mm cubes, tamp each layer 25 times, cure in a moist closet for 24 hours, then store in water for 4 days.
• Testing: Test cubes at 4 days; average compressive strength is 25 MPa.
• Interpretation: Compare the strength to project specifications (e.g., >20 MPa for general concrete). The sand is suitable if it meets or exceeds the required strength.

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Key Tips for Students and Engineers

• Ensure Proper Flow: Achieving a flow of 100 ± 5 is critical for consistent mortar consistency. Adjust sand quantity carefully.
• Control Curing Conditions: Maintain 27 ± 2°C in the moist closet and water storage to ensure reliable curing.
• Clean Specimens Properly: Remove loose sand without damaging the surface layer to ensure accurate compressive strength results.
• Use Correct Moulds: Per Amendment No. 2, use 50-mm cube moulds (not 70-mm or 7.06-cm, as mentioned in earlier versions).
• Avoid Sodium Hydroxide Residue: Thorough rinsing and indicator checks are essential to prevent chemical interference with mortar properties.

Common Mistakes to Avoid

• Incorrect Flow Adjustment: Adding too much sand or discarding batches unnecessarily can skew results.
• Improper Tamping: Inconsistent tamping pressure can lead to uneven specimen density.
• Curing Errors: Deviations from 27 ± 2°C or improper curing duration can affect strength results.
• Surface Preparation: Failing to grind curved specimen faces or testing with loose sand can lead to inaccurate compressive strength readings.
• Typographical Confusion: The document’s mention of “700 cm cubes” is likely a typo; use 50-mm cubes per Amendment No. 2.

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Notes on Document Issues

• Typographical Errors: The document contains errors like “18 2 2866” instead of “IS 2386” and “AGREGATES” instead of “AGGREGATES”. The mention of “700 cm cubes” is likely a typo for 50-mm cubes, corrected in Amendment No. 2 (1991).
• Truncation: Large portions of the document are truncated, limiting procedural details. Consult the full IS 2386 (Part VI) - 1963 for complete information.
• Amendments: Amendment No. 2 (1991) updates the tamping bar and mould specifications. Ensure compliance with these updates.
• Reference Standards: Follow IS 1273:1960 (flow table), IS 4031:1962 (moulds), and IS 2386 (Part II) - 1963 (sodium hydroxide washing) for accurate testing.
• Year Discrepancy: References to “2366” or “1968” are likely typos for IS 2386 and 1963, respectively.

For the complete procedure and additional details, refer to the full IS 2386 (Part VI) - 1963 document, including Amendments No. 1 and 2.

Simplified Guide to the Soundness Test for Aggregates (IS 2386 Part V - 1963)

 IS.2386.5.1963

Simplified Guide to the Soundness Test for Aggregates (IS 2386 Part V - 1963)

The soundness test evaluates the durability of aggregates against weathering, particularly freeze-thaw cycles and chemical attack, which can cause disintegration. This is critical for ensuring aggregates used in concrete can withstand environmental stresses in structures like roads, bridges, and buildings.

Why Test Soundness?

Aggregates are exposed to harsh environmental conditions, such as freezing and thawing or wet-dry cycles, which can cause cracking, splitting, or crumbling. The soundness test simulates these conditions to ensure aggregates remain intact, maintaining the structural integrity and longevity of concrete.

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Soundness Test Overview

What It Measures

The test measures the resistance to disintegration of aggregates when subjected to repeated cycles of immersion in a saturated sodium sulphate or magnesium sulphate solution, followed by drying. The percentage of material lost (passing a specified sieve) indicates the aggregate’s soundness.

Why It Matters

• Aggregates with low soundness loss are more durable and suitable for concrete exposed to weathering, such as in pavements or marine structures.
• High soundness loss indicates poor durability, which could lead to concrete deterioration over time.
• The test helps when service records of aggregates under actual weathering conditions are unavailable.

Key Notes

• Sodium sulphate and magnesium sulphate produce different results, so specifications must define appropriate limits for each.
• The test is more severe for closely sized aggregates than for graded aggregates, affecting limit specifications.

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Apparatus

1. Sieves (conforming to IS 460-1962):
   • Fine Series: 150, 300, 600 microns, 1.18 mm, 2.36 mm, 4.00 mm, 4.75 mm.
   • Coarse Series: 8.0 mm, 10 mm, 12.5 mm, 16 mm, 20 mm, 25 mm, 31.5 mm, 40 mm, 50 mm, 63 mm.
2. Containers: Perforated (e.g., wire mesh baskets or sieves) to allow solution access and drainage without aggregate loss.
3. Temperature Regulation: To maintain samples at 27 ± 1°C during immersion.
4. Balances:
   • Fine aggregates: ≥500 g capacity, sensitive to 0.1 g.
   • Coarse aggregates: ≥5000 g capacity, sensitive to 1 g.
5. Drying Oven: Maintained at 105–110°C, with an evaporation rate of at least 25 g/h for 4 hours (tested with 500 g water in 1-litre beakers).

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Reagents

1. Sodium Sulphate Solution:
   • Prepare a saturated solution using technical-grade sodium sulphate (IS 255-1950), anhydrous (Na₂SO₄) or crystalline (Na₂SO₄·10H₂O).
   • Dissolve at 25–30°C, using ≥420 g anhydrous or ≥1300 g decahydrate per litre of water to ensure excess crystals.
   • Cool to 27 ± 2°C for 48 hours, stir frequently, and check specific gravity (1.151–1.174). Discard or filter discoloured solutions.
2. Magnesium Sulphate Solution:
   • Prepare using technical-grade magnesium sulphate (IS 257-1950), anhydrous (MgSO₄) or crystalline (MgSO₄·7H₂O, Epsom salt).
   • Dissolve at 25–30°C, using ≥400 g anhydrous or ≥1400 g heptahydrate per litre of water.
   • Cool to 27 ± 1°C for 48 hours, stir frequently, and check specific gravity (1.295–1.308). Discard or filter discoloured solutions.

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Sample Preparation

1. Fine Aggregate:
   • Wash on a 300-micron sieve, dry to constant weight at 105–110°C.
   • Sieve into fractions (150 micron to 4.75 mm, as per 4.1). Select ~110 g per fraction, sieve to refusal, and use 100 g samples.
2. Coarse Aggregate:
   • Wash and dry to constant weight at 105–110°C.
   • Sieve into fractions (4.75 mm to 80 mm, as per 4.2). Use specified weights:
     • 10–4.75 mm: 300 g
     • 20–10 mm: 1000 g (33% 12.5–10 mm, 67% 20–12.5 mm)
     • 40–20 mm: 1500 g (33% 25–20 mm, 67% 40–25 mm)
     • 63–40 mm: 3000 g (50% 50–40 mm, 50% 63–50 mm)
     • ≥80 mm: 3000 g per 20-mm size fraction
   • Count particles for fractions >20 mm.
3. All-in-Aggregate:
   • Separate into fine (<4.75 mm) and coarse (>4.75 mm) fractions, testing each as above.
4. Note on Small Fractions:
   • If a size fraction is <5% of the sample, assume its loss equals the average of the next smaller and larger sizes (or the nearest size if one is absent).

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Test Procedure

1. Immersion:
   • Immerse samples in sodium or magnesium sulphate solution for 16–18 hours, ensuring ≥15 mm solution coverage and a solution-to-sample volume ratio of ≥5:1.
   • Maintain temperature at 27 ± 1°C. Cover containers to minimize evaporation.
2. Drying:
   • Drain samples for 15 ± 5 minutes, then dry at 105–110°C to constant weight (successive weights within 0.1 g for fine, 1 g for coarse aggregates).
   • Cool to room temperature.
3. Cycles:
   • Repeat immersion and drying for the number of cycles agreed upon by the purchaser and vendor (typically 5 cycles, per common practice).
4. Quantitative Examination:
   • After the final cycle, wash samples until free of sulphate (test wash water with barium chloride).
   • Dry to constant weight at 105–110°C.
   • Sieve fine aggregates over their original sieve, coarse aggregates over specified sieves:
     • 63–40 mm: 31.5 mm
     • 40–20 mm: 16 mm
     • 20–10 mm: 8.0 mm
     • 10–4.75 mm: 4.0 mm
   • Calculate loss as the percentage of material passing the sieve.
5. Qualitative Examination (for >20 mm fractions):
   • After each immersion, observe effects (e.g., disintegration, splitting, crumbling, cracking, flaking).
   • At test end, count affected particles and classify the type of damage.

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Reporting Results

Include:

1. Weight of each fraction before testing.
2. Percentage loss for each fraction (material passing the specified sieve).
3. Weighted average loss based on the sample’s grading or the supply’s average grading (assume 0% loss for <300-micron fractions).
4. For >20 mm fractions: number of particles before testing and number affected (by disintegration, splitting, etc.).
5. Type of solution used (sodium or magnesium sulphate).

Example Table (Table I from the Standard)

 

Simplified Guide for Testing Aggregates for Concrete (IS 2386 Part IV)

 IS.2386.4.1963

Simplified Guide for Testing Aggregates for Concrete (IS 2386 Part IV)

This guide explains the mechanical property tests for aggregates as per IS 2386 (Part IV) - 1963, focusing on aggregate crushing value, aggregate impact value, abrasion value, and crushing strength. These tests assess the strength and durability of aggregates, critical for ensuring concrete quality in construction projects like buildings, roads, and bridges.

Why Test Mechanical Properties of Aggregates?

Aggregates constitute 60-75% of concrete’s volume, and their mechanical properties directly influence the concrete’s strength, durability, and resistance to wear. Testing ensures aggregates can withstand the stresses of mixing, placement, and service conditions.

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1. Aggregate Crushing Value (ACV) Test

What It Measures

The aggregate crushing value indicates the resistance of an aggregate to crushing under a gradually applied compressive load. A lower ACV indicates a stronger aggregate.

Why It Matters

• Aggregates with high crushing strength are essential for high-strength concrete used in structures like bridges or high-rise buildings.
• Weak aggregates can lead to concrete failure under load.

How to Test

1. Apparatus:
   • A 15-cm diameter open-ended steel cylinder with a plunger and base plate (or a 75-mm cylinder for smaller aggregates), as shown in Fig. 1 of the standard.
   • A tamping rod (16 mm diameter, 45-60 cm long, rounded at one end).
   • A compression testing machine capable of applying 40 tons in 10 minutes.
   • IS sieves (12.5 mm, 10 mm, and 2.36 mm).
   • A balance accurate to 1 gram.
2. Procedure:
   • Use aggregates passing the 12.5-mm sieve and retained on the 10-mm sieve, in a surface-dry condition. If dried, heat at 100-110°C for no more than 4 hours and cool to room temperature.
   • Fill the cylinder in three equal layers, tamping each layer 25 times with the tamping rod to a depth of 10 cm.
   • Level the surface, weigh the sample, and place the cylinder in the compression testing machine.
   • Apply a load of 40 tons over 10 minutes.
   • Sieve the crushed material through a 2.36-mm sieve and weigh the material passing (fines).
   • Calculate ACV = [(Weight of fines passing 2.36-mm sieve) / (Total weight of sample)] × 100%, reported to the nearest whole number.
3. Notes:
   • Larger aggregates typically have higher ACV, indicating lower resistance to crushing.
   • Conduct a duplicate test using the same weight of material for accuracy.

Real-Life Example

For a highway pavement project, you test coarse aggregates and find an ACV of 20%. This indicates that 20% of the material is crushed into fines under the test load. If the project specification requires an ACV below 25% for road aggregates, your material is suitable, ensuring the pavement can withstand heavy traffic loads.

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2. Aggregate Impact Value (AIV) Test

What It Measures

The aggregate impact value measures the resistance of aggregates to sudden impact or shock, simulating dynamic loads like those from traffic or blasting.

Why It Matters

• Aggregates with low AIV are tougher and better suited for applications like road bases or railway ballast, where sudden loads are common.
• High AIV indicates brittle aggregates, which may fail under impact.

How to Test

1. Apparatus:
   • An impact testing machine with a total weight of 60 kg, including a metal base (22-30 kg) and a cylindrical cup (as shown in Fig. 2).
   • A tamping rod (16 mm diameter, 50-60 cm long, rounded at one end).
   • IS sieves (12.5 mm, 10 mm, and 2.36 mm).
   • A balance accurate to 1 gram.
2. Procedure:
   • Use aggregates passing the 12.5-mm sieve and retained on the 10-mm sieve, in a surface-dry condition.
   • Fill the cup in three layers, tamping each layer 25 times. Strike off surplus aggregate.
   • Fix the cup firmly on the machine’s base. Raise the hammer (weighing 13.5-14 kg) to 380 mm and allow it to fall freely 15 times.
   • Sieve the material through a 2.36-mm sieve and weigh the fines.
   • Calculate AIV = [(Weight of fines passing 2.36-mm sieve) / (Total weight of sample)] × 100%.

Real-Life Example

For a railway ballast project, you test aggregates and find an AIV of 15%. The specification requires an AIV below 20% for ballast to resist train vibrations. Your aggregates pass, ensuring durability under dynamic loads.

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3. Abrasion Value Test (Using Deval Machine or Los Angeles Machine)

What It Measures

The abrasion value assesses the resistance of aggregates to wear and tear, critical for surfaces exposed to friction, like roads or pavements.

Why It Matters

• Aggregates with low abrasion values are more durable, reducing maintenance costs for roads or runways.
• High abrasion loss indicates aggregates may wear out quickly, affecting surface integrity.

How to Test (Deval Machine)

1. Apparatus:
   • Deval abrasion testing machine with hollow cast iron cylinders (20 cm diameter, 34 cm deep), rotated at 30° to the shaft.
   • IS sieve (1.70 mm).
   • Abrasive charge: 6 cast iron or steel spheres (48 mm diameter, 390-415 g each, total 2500 ± 10 g).
   • A balance accurate to 1 gram.
2. Procedure:
   • Prepare a test sample based on specific gravity:
     • Over 2.8: 5500 g
     • 2.4-2.8: 5000 g
     • 2.2-2.4: 4500 g
     • Less than 2.2: 4000 g
   • Sieve aggregates to the required grading (as per Part III of the standard), wash, and dry.
   • Place the sample and abrasive charge in the cylinder and rotate for 10,000 revolutions at 30-33 rpm.
   • Sieve the material through a 1.70-mm sieve and weigh the fines.
   • Calculate Abrasion Value = [(Weight of fines passing 1.70-mm sieve) / (Total weight of sample)] × 100%.

How to Test (Los Angeles Machine)

1. Apparatus:
   • Los Angeles abrasion testing machine with a hollow steel cylinder (as shown in Fig. 3).
   • IS sieve (1.70 mm).
   • Abrasive charge: Steel spheres (48 mm diameter, 390-445 g each), with the number and weight varying by grading (e.g., 12 spheres for Grading A, 5000 ± 25 g).
2. Procedure:
   • Prepare a test sample (e.g., 5000 g for Gradings A-D, 10,000 g for Gradings E-G) based on grading specified in the standard.
   • Place the sample and abrasive charge in the cylinder and rotate for 500 revolutions (Gradings A-D) or 1000 revolutions (Gradings E-G) at 20-33 rpm.
   • Sieve the material through a 1.70-mm sieve and weigh the fines.
   • Calculate Abrasion Value = [(Weight of fines passing 1.70-mm sieve) / (Total weight of sample)] × 100%.

Real-Life Example

For a runway project, you test aggregates using the Los Angeles machine and find an abrasion value of 25%. The specification requires a value below 30% for pavement aggregates. Your aggregates are suitable, ensuring the runway surface resists wear from aircraft landings.

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4. Crushing Strength Test

What It Measures

The crushing strength measures the compressive strength of individual aggregate particles, indicating their ability to resist direct compressive forces.

Why It Matters

• This test is critical for aggregates used in high-strength concrete, such as in dams or heavy-duty structures.
• It helps identify weak aggregates that could fail under load.

How to Test

1. Apparatus:
   • A compression testing machine with a spherical seating platen (radius ≤ 2 cm).
   • A well-ventilated, thermostatically controlled oven (100-110°C).
2. Procedure:
   • Select individual aggregate particles (e.g., passing 12.5-mm sieve, retained on 10-mm sieve).
   • Dry the particles in the oven for 4 hours and cool to room temperature.
   • Test each particle under compression, recording the load at failure.
   • Calculate the crushing stress for each particle and report the average to the nearest 5 kg/cm².
   • Note any defects (e.g., seams, fissures) that may affect results.

Real-Life Example

For a dam project, you test granite aggregates and find an average crushing strength of 1000 kg/cm². The design requires aggregates with a minimum strength of 800 kg/cm² to withstand the dam’s compressive loads. Your aggregates meet the requirement, ensuring structural integrity.

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Key Tips for Students and Engineers

• Select Appropriate Tests: Choose tests based on project needs (e.g., ACV for structural concrete, AIV for roads, abrasion for pavements).
• Ensure Proper Calibration: Use calibrated equipment (e.g., sieves, compression machines) for accurate results.
• Consider Aggregate Type: Crushed aggregates (e.g., granite) typically have lower ACV and AIV than uncrushed gravel, affecting test outcomes.
• Follow Standards Strictly: Adhere to IS 2386 (Part IV) for precise procedures and calculations.

Common Mistakes to Avoid

• Improper Sample Preparation: Failing to dry aggregates to a surface-dry condition can skew results.
• Inconsistent Tamping: Uneven tamping in ACV or AIV tests can lead to inaccurate measurements.
• Ignoring Grading: Using incorrect aggregate sizes or gradings can invalidate abrasion test results.
• Overlooking Defects: Not noting flaws like fissures in crushing strength tests can misrepresent aggregate quality.

Practical Application

Imagine you’re designing concrete for a high-rise building. You test the aggregates:

• ACV: 18% (suitable for structural concrete, <30%).
• AIV: 15% (suitable for dynamic loads, <20%).
• Los Angeles Abrasion: 22% (suitable for pavements, <30%).
• Crushing Strength: 900 kg/cm² (meets high-strength requirements). These results confirm the aggregates are robust for the building’s foundation, ensuring durability and safety.

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Notes on Document Issues

• The document contains typographical errors (e.g., “AGREAGATES,” “MECHANAL,” “CONCRT”) and inconsistent numbering (e.g., “IS : 2366” vs. “IS : 2386”). Always refer to the official IS 2386 (Part IV) - 1963 for accurate details.
• Some sections are heavily truncated, limiting procedural details. Consult the full standard for complete test methods.
• Amendments (e.g., No. 2, September 1981; No. 3, October 1983) update apparatus specifications, such as referencing IS 9376-1979 for the crushing value apparatus.

For detailed procedures and calculations, refer to the full IS 2386 (Part IV) - 1963 document.

 

 IS.2386.3.1963

Simplified Guide for Testing Aggregates for Concrete (IS 2386 Part III)

This guide simplifies the key tests outlined in IS 2386 (Part III) - 1963 for students and engineers. It covers methods to test aggregates used in concrete, focusing on specific gravity, water absorption, bulk density, voids, bulking, and surface moisture. Real-life examples are included to make the concepts practical and easy to understand.

Why Test Aggregates?

Aggregates (sand, gravel, or crushed stone) make up 60-75% of concrete’s volume. Their properties affect the strength, durability, and workability of concrete. Testing ensures aggregates meet quality standards for construction projects like buildings, roads, or bridges.

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1. Specific Gravity and Water Absorption

What It Measures

• Specific Gravity: The ratio of the aggregate’s weight to the weight of an equal volume of water. It indicates how dense the aggregate is.
• Water Absorption: The amount of water an aggregate can absorb, which affects the water needed in the concrete mix.

Why It Matters

• Specific gravity helps calculate the correct mix proportions.
• High water absorption can increase the water demand, weakening the concrete if not accounted for.

How to Test

• For Aggregates Larger than 10 mm (Method I):

  1. Take a sample (e.g., 2 kg of gravel).
  2. Soak it in water for 24 hours.
  3. Weigh the sample in water (suspended in a basket) and after surface-drying.
  4. Dry it in an oven at 100-110°C and weigh again.
  5. Calculate:
     • Specific Gravity = (Dry weight) / (Dry weight - Weight in water)
     • Water Absorption = [(Saturated surface-dry weight - Dry weight) / Dry weight] × 100%

• For Aggregates Smaller than 10 mm (Method III):

  1. Use a pycnometer (a glass jar with a tight lid).
  2. Fill with a sample (e.g., 1 kg of sand), add water, and weigh.
  3. Dry the sample and weigh again.
  4. Use formulas to calculate specific gravity and absorption.

Real-Life Example

Imagine you’re building a concrete slab for a parking lot. You test gravel and find its specific gravity is 2.65 and water absorption is 2%. This means you need to add extra water (2% of the gravel’s weight) to the mix to prevent the gravel from absorbing water meant for cement hydration, ensuring the concrete sets properly.

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2. Bulk Density and Voids

What It Measures

• Bulk Density: The weight of aggregate per unit volume (kg/m³).
• Voids: The empty spaces between aggregate particles, expressed as a percentage.

Why It Matters

• Bulk density helps determine how much aggregate is needed to fill a given volume.
• Voids affect the amount of cement paste required to fill gaps, impacting cost and strength.

How to Test

1. Use a calibrated container (e.g., a 15-liter bucket).
2. Fill it with aggregate in three layers, tamping each layer 25 times with a rod.
3. Level the surface and weigh the container with the aggregate.
4. Calculate:
   • Bulk Density = (Weight of aggregate) / (Volume of container)
   • Voids = [(Specific gravity × Density of water - Bulk density) / (Specific gravity × Density of water)] × 100%

Real-Life Example

For a road construction project, you test coarse aggregate and find a bulk density of 1600 kg/m³ and voids of 40%. This means 40% of the volume is air, so you’ll need more cement paste to fill those gaps, increasing the mix cost. Compacting the aggregate better could reduce voids and save materials.

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3. Bulking of Fine Aggregate (Field Method)

What It Measures

The increase in volume of fine aggregate (sand) due to moisture, which causes particles to push apart.

Why It Matters

Bulking can lead to incorrect mix proportions. If you measure wet sand by volume, you might add less sand than needed, weakening the concrete.

How to Test

1. Fill a container with dry sand and measure its volume.
2. Add water to simulate moisture (e.g., 2%, 4%, etc.).
3. Measure the new volume of the wet sand.
4. Calculate Bulking = [(Wet volume - Dry volume) / Dry volume] × 100%

Real-Life Example

You’re mixing concrete for a house foundation. Testing shows wet sand bulks by 20%. If you need 1 m³ of dry sand, you must measure 1.2 m³ of wet sand to account for bulking, ensuring the correct amount of sand in the mix.

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4. Surface Moisture in Fine Aggregate (Field Method)

What It Measures

The amount of water on the surface of fine aggregate, which adds to the mix’s water content.

Why It Matters

Excess surface moisture can increase the water-cement ratio, reducing concrete strength.

How to Test

1. Take a sample of wet sand (e.g., 500 g).
2. Dry it in an oven at 100-110°C until all surface moisture evaporates.
3. Weigh the dry sample.
4. Calculate Surface Moisture = [(Wet weight - Dry weight) / Dry weight] × 100%

Real-Life Example

While preparing concrete for a bridge column, you find the sand has 5% surface moisture. For 1000 kg of sand, that’s 50 kg of extra water. You reduce the mixing water by 50 kg to maintain the designed water-cement ratio, ensuring the concrete’s strength.

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Key Tips for Students and Engineers

• Choose the Right Test: Not all tests are needed for every project. For example, focus on water absorption for porous aggregates or bulking for fine sand in humid areas.
• Use Proper Equipment: Ensure ovens, pycnometers, and containers are calibrated for accurate results.
• Understand the Context: Test results depend on the aggregate type (e.g., granite vs. limestone) and project requirements (e.g., high-strength concrete for bridges vs. low-strength for pavements).
• Follow Standards: Always refer to IS 2386 (Part III) for detailed procedures and calculations.

Common Mistakes to Avoid

• Ignoring Bulking: Measuring wet sand by volume without adjusting for bulking can lead to weak concrete.
• Incomplete Drying: Not drying aggregates fully during testing can skew specific gravity and absorption results.
• Poor Compaction: Inconsistent tamping during bulk density tests can give incorrect void percentages.

Practical Application

Imagine you’re an engineer on a dam project. You test the aggregates:

• Gravel: Specific gravity = 2.7, Water absorption = 1.5%.
• Sand: Bulk density = 1500 kg/m³, Bulking = 15%, Surface moisture = 4%.
  You adjust the mix design to account for the extra water from absorption and surface moisture, reduce sand volume to correct for bulking, and use bulk density to estimate material quantities. This ensures the dam’s concrete is strong and durable.

This guide provides a starting point. For detailed procedures, refer to IS 2386 (Part III) - 1963.

 

 IS.2386.2.1963

Simplified Guide to IS 2386 (Part II) - 1963: Methods of Test for Aggregates for Concrete - Part II: Estimation of Deleterious Materials and Organic Impurities

This guide explains IS 2386 (Part II) - 1963, the Indian Standard for testing aggregates for concrete, focusing on deleterious materials and organic impurities, in a clear and concise manner for students and engineers. It includes examples, procedures, and references to clarify the test methods. Due to OCR errors and truncated sections in the provided document, this guide uses reliable information and standard industry knowledge to address gaps.

Why This Standard Matters

IS 2386 (Part II) - 1963, adopted by the Bureau of Indian Standards (BIS) on 22 August 1963 (reaffirmed 2011, with an amendment in February 1983), specifies test methods for assessing deleterious materials and organic impurities in aggregates used in concrete. These materials, such as clay, silt, coal, lignite, soft particles, and organic impurities, can adversely affect concrete’s strength, durability, and workability, making this standard critical for construction projects like buildings, roads, and dams.

Key Benefit: The standard provides standardized procedures to ensure aggregates are free from harmful substances, ensuring high-quality concrete production. It aligns with international standards (e.g., British Standards Institution, American Society for Testing and Materials) and local practices.

References: [IS 2386 (Part II) - 1963, Foreword, Page 8; Clause 1, Page 9]

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Key Sections Explained

1. Scope: What’s This About?

This standard covers five test methods for aggregates used in concrete:

• Determination of Clay Lumps: Measures the percentage of clay lumps that can be broken down by hand.
• Determination of Clay, Fine Silt, and Fine Dust (Sedimentation Method): Quantifies fine particles (up to 20 microns) using a gravimetric sedimentation method.
• Determination of Light-Weight Pieces (Coal and Lignite): Assesses the percentage of coal and lignite using sink-float separation.
• Determination of Soft Particles: Identifies soft particles in coarse aggregates based on scratch-hardness.
• Estimation of Organic Impurities: Checks for harmful organic compounds in fine aggregates by color comparison.

Example for Students: These tests are like checking for unwanted ingredients in a recipe that could ruin the concrete mix.
Example for Engineers: Use these tests to ensure aggregates for a high-rise building foundation meet IS 383:2016 limits for deleterious materials (e.g., ≤1% clay lumps for fine aggregates).

Reference: [IS 2386 (Part II) - 1963, Clause 1.1, Page 9]

2. Foreword: Context and Purpose

The standard, developed by the Cement and Concrete Sectional Committee (BDC 2), emphasizes the importance of aggregate quality in concrete performance. It is part of an eight-part series (IS 2386:1963) covering various aggregate tests (e.g., particle size, specific gravity, soundness). The tests in Part II help identify deleterious materials and organic impurities that could compromise concrete quality.

Key Features:

• Aligns with international standards (e.g., BSI, ASTM).
• References the latest versions of Indian Standards (e.g., IS 460-1962 for test sieves).
• Numerical values are rounded per IS 2:1960.
• Focuses on technical provisions, not contractual details.

Example: The standard ensures aggregates for a dam project are free from clay or coal, preventing issues like reduced strength or staining.

Reference: [IS 2386 (Part II) - 1963, Foreword, Pages 8–9]

3. Determination of Clay Lumps (Clause 2)

Object: Determines the approximate percentage of clay lumps in aggregates, as these can weaken concrete by absorbing water or disintegrating.

Apparatus:

• Balance: Accurate to 0.1% of sample weight.
• Containers: For spreading samples in a thin layer.
• Sieves: Per IS 460-1962 (e.g., 1.18-mm, 4.75-mm).

Sample:

• Fine Aggregate: Particles coarser than 1.18-mm IS Sieve, minimum 100 g.
• Coarse Aggregate: Separated into sizes (4.75–10 mm: 1000 g; 10–20 mm: 2000 g; 20–40 mm: 3000 g; >40 mm: 5000 g).
• Dry to constant weight at ≤110°C.
• Prepare by quartering or using a sampler, avoiding breaking clay lumps.

Procedure:

1. Spread the sample in a thin layer in a container.
2. Identify and break clay lumps (particles that crumble into fine particles with finger pressure).
3. Sieve residue through specified sieves (e.g., 850-micron for fine aggregate, 4.75-mm for coarse aggregate >20 mm).
4. Calculate percentage of clay lumps:
   [
   L = \frac{W - R}{W} \times 100
   ]
   where ( L ) = percentage of clay lumps, ( W ) = original sample weight, ( R ) = weight after removing clay lumps.

Reporting: Report to the nearest 0.1%.

Example for Students: Clay lumps are like clumps of mud in sand that need to be removed to keep concrete strong.
Example for Engineers: Ensure fine aggregate for a pavement has ≤1% clay lumps (per IS 383:2016, Table 2) to avoid water absorption issues.

References: [IS 2386 (Part II) - 1963, Clauses 2.1–2.6, Pages 9–11]

4. Determination of Clay, Fine Silt, and Fine Dust (Sedimentation Method) (Clause 3)

Object: Measures the content of clay, fine silt, and fine dust (up to 20 microns) in aggregates, as these increase water demand and reduce concrete strength.

Apparatus:

• Glass Jar: 1-kg fruit-preserving jar, watertight, screw-topped.
• Rotating Device: Rotates jar at 80 ± 20 rpm.
• Sedimentation Pipette: Andreason type, ~25 ml capacity (Fig. 1).
• Measuring Cylinder: 1000-ml.
• Balances: 10 kg (accurate to 1 g), 250 g (accurate to 0.001 g).
• Oven: 100–110°C.

Chemicals: 8 g/L sodium oxalate solution, diluted to 0.8 g/L for testing.

Sample:

• Minimum weights (Table I):
  • 63–25 mm: 6 kg
  • 20–12.5 mm: 1 kg
  • 10–6.3 mm: 0.5 kg
  • ≤4.75 mm: 0.3 kg
• Separate all-in aggregates into fine and coarse fractions using a 4.75-mm IS Sieve.

Procedure:

1. Fine Aggregate:
   • Weigh 300 g (air-dry, passing 4.75-mm sieve).
   • Place in jar with 300 ml diluted sodium oxalate solution.
   • Rotate at 80 ± 20 rpm for 15 minutes.
   • Pour suspension into a 1000-ml cylinder, wash residue with 150-ml portions of solution until the volume reaches 1000 ml.
2. Coarse Aggregate:
   • Place sample in a container, cover with 0.8 g/L sodium oxalate solution, agitate to remove fine material, and transfer suspension to a 1000-ml cylinder.
   • Repeat until all clayey material is transferred, make up to 1000 ml.
3. Sedimentation:
   • Mix suspension in the cylinder by inversion.
   • Lower pipette 10 cm into the liquid 3 minutes after mixing.
   • Draw a sample into the pipette, transfer to a weighed container, wash with distilled water, dry at 100–110°C, and weigh.
4. Calculate percentage of clay, fine silt, and fine dust:
   [
   \text{Percentage} = \frac{100}{W_1} \left( \frac{1000 W_2}{V} - 0.8 \right)
   ]
   where ( W_1 ) = original sample weight (g), ( W_2 ) = dried residue weight (g), ( V ) = pipette volume (ml), 0.8 = sodium oxalate weight in 1 L solution.

Reporting: Report to the nearest 0.1%.

Example for Students: This test is like filtering out tiny dirt particles from sand to ensure clean concrete.
Example for Engineers: Ensure fine aggregate for a bridge has ≤3% fine silt and dust (per IS 383:2016, Table 2) to maintain workability.

References: [IS 2386 (Part II) - 1963, Clauses 3.1–3.7, Pages 11–15]

5. Determination of Light-Weight Pieces (Coal and Lignite) (Clause 4)

Object: Determines the percentage of light-weight pieces (coal and lignite) in aggregates, as these reduce concrete strength and cause staining.

Apparatus:

• Balances: 500 g (0.1 g accuracy) for fine aggregates, 5000 g (1 g accuracy) for coarse aggregates.
• Containers: For drying and holding heavy liquid.
• Skimmer: 300-micron sieve cloth.
• Hot-Plate or Oven.

Heavy Liquid:

• Mixture of carbon tetrachloride, 1,1,2,2-tetrabromoethane, bromoform, monobromobenzene, or bromoform-benzene, adjusted to a specific gravity of 2.00 ± 0.01.
• Specific gravities: Tetrabromoethane (2.97), bromoform (2.88), carbon tetrachloride (1.58), monobromobenzene (1.49), benzene (0.88).
• Caution: These chemicals are toxic; use in a hood, avoid skin contact and inhalation.

Sample:

• Minimum weights:
  • 6.3 mm (fine): 200 g
  • 20 mm: 3000 g
  • 40 mm: 5000 g
  • 80 mm: 10000 g

Procedure:

1. Fine Aggregate:
   • Dry and cool the sample, sieve over a 300-micron IS Sieve.
   • Weigh material coarser than 300-micron.
   • Place in heavy liquid (volume ≥3 times aggregate volume), decant floating pieces onto skimmer.
   • Repeat agitation and decanting until no pieces float.
   • Wash decanted pieces with carbon tetrachloride, dry, and weigh to 0.1 g.
2. Coarse Aggregate:
   • Dry and cool, sieve over a 4.75-mm IS Sieve.
   • Weigh material coarser than 4.75-mm.
   • Place in heavy liquid, remove floating pieces with skimmer, repeat until no pieces float.
   • Wash, dry, and weigh decanted pieces to 1 g.
3. Calculate percentage of light-weight pieces:
   • Fine aggregate: ( L = \frac{W_1}{W_2} \times 100 )
   • Coarse aggregate: ( L = \frac{W_1}{W_3} \times 100 )
     where ( W_1 ) = weight of decanted pieces, ( W_2 ) = weight coarser than 300-micron, ( W_3 ) = weight coarser than 4.75-mm.

Reporting: Report to the nearest 0.1%.

Example for Students: Coal and lignite float because they’re lighter than sand or gravel, and this test removes them to keep concrete strong.
Example for Engineers: Ensure coarse aggregate for a dam has ≤0.5% coal and lignite (per IS 383:2016, Table 2) to avoid staining and strength loss.

References: [IS 2386 (Part II) - 1963, Clauses 4.1–4.7, Pages 15–17]

6. Determination of Soft Particles (Clause 5)

Object: Identifies soft particles in coarse aggregates (≥10 mm) by scratch-hardness, as these can reduce concrete durability.

Apparatus: Brass rod (1.6 mm diameter, Rockwell hardness 65–75 RHB), often inserted into a pencil for ease of use.

Sample:

• Remove particles <10-mm IS Sieve.
• Minimum weights for sizes (≥10% of sample):
  • 10–12.5 mm: 200 g
  • 12.5–20 mm: 600 g
  • 20–25 mm: 1500 g
  • 25–40 mm: 4500 g
  • 40–50 mm: 12000 g
• If a size has <10% material, assume it has the same soft particle percentage as the average of adjacent sizes.

Procedure:

1. Scratch each particle with the brass rod using ~1 kg pressure.
2. Classify particles as soft if a groove is made without brass deposition or if particles detach from the mass.
3. Record weight and number of soft and total particles per size fraction.

Reporting:

• Weight and number of particles tested and classified as soft per size.
• Percentage of soft particles by weight and number.
• Weighted average percentage based on sample grading (exclude <10-mm sizes).

Example for Students: Soft particles are like weak rocks that crumble easily, making concrete less durable.
Example for Engineers: For a bridge pier, ensure soft particles are minimal (e.g., ≤1%) to maintain structural integrity.

Reference: [IS 2386 (Part II) - 1963, Clauses 5.1–5.5, Pages 18–19]

7. Estimation of Organic Impurities (Clause 6, Amended 1983)

Object: Approximates the presence of harmful organic compounds in natural sand by color comparison, indicating if further tests (e.g., IS 2386 Part VI) are needed.

Procedure:

1. Fill a 350-ml clear glass medicine bottle to 75 ml with 3% sodium hydroxide (NaOH) solution.
2. Add undried sand until the sand layer reaches 125 ml.
3. Add more NaOH solution to reach 200 ml.
4. Stopper, shake vigorously, and let stand for 24 hours.
5. Compare the color of the liquid above the sand to a standard solution:
   • Prepare standard: Mix 2.5 ml of 2% tannic acid (in 10% alcohol) with 97.5 ml of 3% NaOH solution, shake, and let stand for 24 hours.
   • If the sample liquid is darker than the standard, further tests are required (e.g., mortar strength test per IS 2386 Part VI).
   • Alternatively, use a color comparison instrument or verified acetate sheets.

Note: Harmless organic materials may cause coloration, and some harmful ones may not.

Example for Students: This test is like checking if sand has invisible “dirt” that could harm concrete by seeing if the water turns too dark.
Example for Engineers: If the test shows a dark color, conduct further tests to confirm organic impurities are below harmful levels (per IS 383:2016).

References: [IS 2386 (Part II) - 1963, Clauses 6.1–6.2, Pages 19–20; Amendment 1, Page 7]

8. Committee Composition (Pages 5–6)

The Cement and Concrete Sectional Committee (BDC 2) included experts from:

• The Concrete Association of India, M.N. Dastur & Co., Bhakra Dam Designs Directorate, ACC Ltd., Gammon India Ltd., and others.

Example: The committee’s expertise ensures practical and reliable test methods for real-world applications.

Reference: [IS 2386 (Part II) - 1963, Pages 5–6]

9. Amendment (Page 7)

• Amendment No. 1 (1983): Revised Clause 6.1 to clarify that the organic impurities test is approximate and indicates the need for further tests (e.g., IS 2386 Part VI). Added notes on harmless coloration and non-coloring organic compounds.

Example for Engineers: Check the amendment to ensure proper interpretation of organic impurities test results.

Reference: [IS 2386 (Part II) - 1963, Page 7]

10. Copyright

BIS holds the copyright, so reproduction requires permission. Test methods can be implemented without restriction.

Reference: [IS 2386 (Part II) - 1963, Page 3]

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Practical Tips for Students and Engineers

• Why Use IS 2386 (Part II)?: Ensures aggregates are free from harmful materials like clay, silt, coal, lignite, soft particles, and organic impurities, improving concrete quality.
• Key Steps for Testing:
  1. Conduct clay lumps test to ensure ≤1% for fine aggregates and ≤2% for coarse aggregates (per IS 383:2016, Table 2).
  2. Use sedimentation method to verify fine silt and dust ≤3% for fine aggregates (per IS 383:2016, Table 2).
  3. Check coal and lignite content (≤0.5% for critical structures) to prevent staining and strength loss.
  4. Test for soft particles in coarse aggregates to ensure durability (e.g., ≤1% for high-strength concrete).
  5. Perform organic impurities test to screen fine aggregates; if the color is dark, conduct further strength tests.
• Safety Note: Handle toxic heavy liquids (e.g., bromoform) with care, using a hood and avoiding skin contact or inhalation.
• Quality Control: Use precise equipment (e.g., accurate balances, standard sieves) and follow procedures to avoid errors like sample contamination.
• Integration with IS 383:2016: Cross-reference test results with IS 383:2016 limits (e.g., Table 2 for deleterious materials) for compliance.
• Practical Example:
  • Students: Perform the clay lumps test in a lab to check if sand is clean enough for concrete.
  • Engineers: Test aggregates for a high-rise building to ensure coal and lignite content is ≤0.5% and organic impurities do not require further testing.

References: [IS 2386 (Part II) - 1963, Clauses 2–6, Pages 9–20; IS 383:2016, Table 2]

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Why This Matters

For students, IS 2386 (Part II) - 1963 provides practical methods to understand how deleterious materials affect concrete quality. For engineers, it offers standardized procedures to ensure aggregates meet project specifications, ensuring safe and durable structures. These tests are essential for quality control in construction.