What is the Water permeability test?
Water permeability testing is a critical assessment method to measure a concrete structure's resistance to water ingress, and, based on this accurately estimate the materials resistance to common deterioration mechanisms.
The test evaluates the concrete's porosity, offering insights into its durability, quality, and potential to protect against deterioration from processes such as reinforcement corrosion, carbonation, chloride attack, external sulphate attack, freeze-thaw cycles, and acid attack.
Water permeability testing is therefore a pivotal tool for understanding a structure's longevity and safeguarding against premature degradation by ensuring that constructions can withstand the challenges posed by water and soluble agents such as chlorides and carbonates.
How does the Water permeability test work?
The principle behind air permeability testing of concrete structures involves applying water pressure to the concrete's surface and monitoring volume of water penetrating into the concrete at a constant pressure of 0.5 bar (AutoClam) or measuring the time taken for the water meniscus to travel a distance of 50mm through the concrete (Figg Number).
Devices are usually composed of an inner and an outer vacuum cell and work by applying vacuum pressure in one chamber and recording the pressure change in another.
This method assesses the concrete's porosity and its resistance to water ingress, providing insights into the material's durability, quality, and potential for protecting reinforcement against corrosion and other environmental effects.
What is the Water permeability test used for?
Deterioration process | Defects | Control of repairs |
Variation in quality of concrete | Concrete in-situ quality control (durability indicators) |
How do I carry out the Water permeability test?
While no definitive test standards have been produced for on-site testing of water permeability device manufacturers do provide guidance on how to carry out these tests. Based on this a best practice procedure could be described as follows:
Clean and mark the concrete test area.
Assemble and calibrate the testing device.
Record temperature and humidity, which can impact the test.
Verify the concrete's moisture level for testing readiness.
Drill the required holes if using a Figg type device.
Attach the device and for AutoClam, apply a 0.5 bar pressure to monitor water volume absorption or for the Figg type, insert the probe into a pre-drilled hole to measure the time for water to move 50mm.
Initiate the test, applying constant pressure of 0.5 bar for AutoClam or insert the probe into a pre-drilled hole to measure the time for water to move 50mm through the concrete.
Document the water ingress volume or meniscus travel time.
Remove the device and seal holes to maintain concrete integrity.
Calculate water permeability using collected data.
Benchmark and asses results to assess concrete quality and compile findings with actionable recommendations.
What equipment and expertise are required for the Water permeability test?
A variety of testing equipment and methodologies have been developed, each based on a range of principles designed to measure the water permeability of concrete. Notable examples include the AutoClam from Amphora NDT, and Figg type testers such as the Poroscope Plus from James Instruments with each employing distinct approaches to evaluate the cover concrete's ability to resist the ingress of harmful substances.
Figg type models require a 5.5 mm-diameter hole to be drilled into the concrete, the device then applies water pressure within it and measures the time in seconds it takes for the water meniscus in the probe to drop by 50mm. These small blemishes may mean this device in unsuitable for architectural concrete, concrete in aggressive exposure conditions or for ongoing monitoring of elements over time.
The AutoClam device works in a similar manner by applying 0.5 bar of water pressure to the concrete surface and measuring the volume of water penetrating the concrete over time. The AutoClam however does this on the surface of the concrete with four screws holding it in place.
Designed for versatility across various concrete types and conditions, the AutoClam is user-friendly, requiring no specialized expertise for operation, thus ensuring reliable, consistent results in evaluating concrete's resistance to water and air ingress.
What are the advantages of the Water permeability test?
Allows for a detailed assessment of the concrete's surface condition, providing a metric for evaluating the concrete's potential durability and susceptibility to environmental degradation.
By identifying areas of higher permeability, it enables targeted maintenance, potentially extending the structure's service life and avoiding costly repairs.
Enables comparisons across different sections of a structure or between different structures, based on established benchmarks.
Identifies potential issues early, reducing long-term repair costs.
Acts as a benchmark for concrete quality, ensuring consistency across batches and suppliers.
Provides insights into concrete's resistance to all forms of ingress such as chlorides, sulphates and carbonation, freeze-thaw cycles and chemical attacks, critical in harsh environments.
What are the disadvantages the Water permeability test?
Requires specific surface conditions, making it challenging to test weathered or treated surfaces accurately.
The concrete's internal humidity can affect readings, necessitating additional moisture content assessments.
Different equipment models may yield varying results, complicating comparisons.
Results require expert interpretation to inform meaningful action, potentially limiting utility for non-specialist.
Primarily assesses surface permeability, which may not represent the entire structure's condition.
Results can be affected by surface conditions and moisture.
Concrete surfaces may need to be dried for 48 hours, reducing speed of results, or, suitable corrections made to results based on electrical resistivity and tested moisture levels.
How accurate is the Water permeability test?
The accuracy of water permeability testing in concrete varies with the device used, influenced by factors such as calibration, environmental conditions, and the concrete's surface state.
While specific accuracy figures for methods like Figg, or AutoClam are not directly provided, these methods have their unique approaches affecting precision.
The correlation between water penetration test results and concrete deterioration is however well proven and significant. High water permeability indicates a greater susceptibility to various forms of deterioration, including corrosion and carbonation (Figure ?).
This is because increased water ingress can accelerate the penetration of harmful agents like chlorides and carbon dioxide, which directly contribute to these processes. Therefore, results from water penetration tests can serve as a strong predictive tool for assessing the potential longevity and durability of concrete structures against environmental challenges.
What are the limits of the Water permeability test?
Water permeability tests on concrete structures are not without their challenges and limitations. Issues such as moisture presence and insufficient pressure application, especially in high-performance concretes, can skew results.
Additionally, difficulty in securing the testing instrument tightly to the concrete surface can lead to inaccurate data. Variability in concrete composition and the need for fully cured concrete further complicate testing, with environmental factors like humidity and temperature impacting outcomes.
These factors underscore the importance of a comprehensive approach to assessing concrete's durability and the potential need for complementary testing methods to fully understand a structure's condition.
Ancillary information
Maturity of test: > 10 years
Qualification & interpretation : Inspector and specialist
Service disruption: No
Preliminary works: Yes
Time consumption Medium (one day)
Cost Medium
Access to element 1 face