NABL Accredited · Durability Testing Service
Initial Surface Absorption Test
(Concrete Surface Absorption)
Measurement of the rate of water absorption into the surface of hardened concrete at fixed time intervals — a non-destructive indicator of concrete surface quality, compaction and curing effectiveness.
BS 1881-208
Standard
±5%
Accuracy
7 Days
Report TAT
NABL
Accredited
NABL Accredited Lab · ISO/IEC 17025:2017
Digital Reports via Autovity QLMS
Pan-India · 7 Lab Locations
Est. 2009 · 20,000+ Projects
Overview
What is the Initial Surface Absorption Test (ISAT)?
The Initial Surface Absorption Test (ISAT) measures the flow of water per unit area into concrete through its surface at a constant head of 200mm at specified time intervals (10 min, 30 min, 1 hr and 2 hr). The rate of absorption decreases with time as the near-surface pores fill with water — providing information on surface porosity and quality.
Conducted as per BS 1881-208, ISAT is particularly sensitive to near-surface concrete quality — the zone most critical for durability in aggressive environments. It is used for evaluating the effectiveness of curing, surface treatments, waterproofing coatings and concrete mix design changes on surface absorption.
Non-Destructive Surface Test
ISAT cap bonded to concrete surface — no coring or drilling required.
Multiple Time Intervals
Measurements at 10, 30, 60 and 120 minutes track absorption rate decay.
Curing Effectiveness Assessment
Compares absorption of well-cured vs poorly-cured concrete surfaces.
Surface Treatment Evaluation
Quantifies reduction in surface absorption from sealers, coatings and impregnants.
NABL Certified Reports
All results on NABL-accredited letterhead per BS 1881-208.
Combined Durability Package
ISAT + RCPT + Resistivity + Water permeability for complete durability assessment.
Test in Action
Initial Surface Absorption Test (ISAT) — Site Images
ISAT Cap Sealed to Concrete Surface
200mm Water Head Setup
Flow Rate Measured at 10 and 30 Minutes
Test Procedure
How the Initial Surface Absorption Test (ISAT) is Conducted
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1Surface PreparationConcrete surface dried at 105°C for 72 hours (or air-dried per agreement). Laitance and coatings removed.
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2ISAT Cap BondingCircular ISAT cap (5cm² internal area) sealed to concrete surface with waterproof putty or wax.
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3Water Head ApplicationCap connected to water supply at 200mm constant head. Capillary tube connected to measure flow rate.
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4Flow Rate MeasurementFlow into surface measured at 10, 30, 60 and 120 minutes by observing movement of water meniscus in capillary tube.
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5ISAT Classification & ReportResults in mL/m²/s classified per BS 1881-208 low/average/high absorption categories. NABL report within 7 days.
Standards & Specifications
Applicable Test Standards
| Standard | Title | Scope | Type |
|---|---|---|---|
| BS 1881-208 | Testing Concrete — Recommendations for the Determination of the Initial Surface Absorption of Concrete | ISAT | British Standard |
| IS 9284 | Method of Test for Abrasion Resistance of Concrete | Surface Quality | Indian Standard |
| ASTM C1585 | Standard Test Method for Measurement of Rate of Absorption of Water by Hydraulic Cement Concretes | Water Absorption | ASTM |
| BS EN 13057 | Products and Systems for the Protection and Repair of Concrete — Determination of Resistance to Capillary Absorption | Capillary Absorption | British Standard |
Applications
Where is the CAPO Test Used?
Evaluation of concrete curing effectiveness on bridges and marine structures
Assessment of surface sealer and waterproofing coating performance
Quality control of near-surface concrete in basements and water-retaining structures
Durability assessment of existing concrete facades and parking structures
Research on effect of SCMs and W/C ratio on near-surface concrete quality
Acceptance testing for premium architectural and exposed concrete surfaces
Why Choose Global Lab
Our Advantages
NABL Accredited ReportsLegally valid durability assessment certificates for all project requirements.
Non-Destructive TestingISAT cap bonded to surface — no specimen extraction required.
Curing Study CapabilityMultiple test points before/after curing to quantify improvement.
Combined Durability PackageISAT + RCPT + Water permeability + Resistivity offered together.
Pan-India CoverageTesting across all 7 lab locations.
Fast 7-Day ReportComplete ISAT results and classification within 7 days.