IS 2386:2021 Part 7 is the Indian Standard (BIS) for methods of test for aggregates for concrete - part 7: alkali-aggregate reactivity. This standard details the testing methods to evaluate the potential alkali-aggregate reactivity (AAR) of aggregates intended for use in concrete. It outlines both the chemical method for rapid screening and the long-term mortar bar method for assessing deleterious expansive potential.
Covers methods for determining potential alkali-aggregate reactivity of aggregates, including the mortar bar method and chemical method.
Overview
- Status
- Current
- Usage level
- Specialized
- Domain
- Materials Science — Aggregates and Sand
- Type
- Testing Method
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Practical Notes
! The chemical method is a rapid screening tool; aggregates failing this test should not be outright rejected without confirmation from the more reliable long-term mortar bar test.
! Alkali-aggregate reaction is highly dependent on moisture; therefore, testing is critical for aggregates used in dams, foundations, and marine structures.
! If an aggregate is found to be reactive, risks can often be mitigated by using low-alkali cement or incorporating mineral admixtures like fly ash or GGBS.
Frequently referenced clauses
aggregatesconcretecementalkali-silica
International Equivalents
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Key Values5
Quick Reference Values
mortar bar test temperature38 ± 2 °C
chemical method test temperature80 ± 1 °C
potentially reactive expansion limit> 0.1% at 6 months
hazardous expansion early indicator> 0.05% at 3 months
comparator gauge length250 mm
Key Formulas
Expansion (%) = (Difference in length / Effective gauge length) × 100
Rc = (V1 - V2) × N × 10 (Reduction in alkalinity)
Tables & Referenced Sections
Key Tables
Table 1 - Grading of Aggregates for Mortar Bar Test
Key Clauses
Clause 2 - Chemical Method
Clause 3 - Mortar Bar Method
Clause 3.4 - Measurement of Expansion
Frequently Asked Questions4
How long does the standard mortar bar test take?+
Observations are typically recorded over a long period, with readings taken at 1, 2, 3, 6, 9, and 12 months.
At what temperature are the mortar bars stored during the test?+
They are stored in sealed containers over water at a controlled temperature of 38°C ± 2°C.
What expansion limits indicate a reactive aggregate in the mortar bar test?+
Expansion exceeding 0.05% at 3 months or 0.1% at 6 months generally indicates potentially deleterious reactivity.
What is measured in the chemical method?+
The test measures the reduction in alkalinity (Rc) and the amount of dissolved silica (Sc) after reacting the aggregate with a sodium hydroxide solution.
QA/QC Inspection Templates
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