What is Residual Reactivity to Internal Sulphates (RRIS) testing for concrete?
Residual Reactivity to Internal Sulphates (RRIS) testing is used to evaluate the potential for future expansive reactions in concrete caused by internal sulphate attack.
This test is critical for assessing the long-term durability and integrity of concrete structures, identifying the likelihood and extent of damage that can occur from delayed ettringite formation (DEF) in concrete structures.
By understanding and mitigating these risks, the lifespan of concrete can be significantly extended, ensuring structural safety and functionality.
How does the Residual Reactivity to Internal Sulphates (RRIS) test work?
The test is based on accelerating the DEF process through exposure of concrete samples to high temperatures and humidity before measuring their rate of expansion over time.
What is Residual Reactivity to Internal Sulphates (RRIS) testing used for?
Deterioration process | Defects | Control of repairs |
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How do I carry out Residual Reactivity to Internal Sulphates (RRIS) testing of concrete?
A detailed step-by-step procedure based on general practices and insights from the "Projet de méthode D'essai LPC Nr. 67" a French scientific and technical research public establishment document, adapted to practical application:
Asses the structure to be tested and plan coring schedules to sample areas most at risk of sulphate attack, those showing visible degradation or at determined intervals for structural mapping.
Extract cores from the concrete structure using a diamond-tipped core drill. Typically core diameters between 75 mm to 150 mm and lengths of 200mm are used.
Measure the initial lengths and diameters of the cores using vernier callipers.
Store the extracted cores in sealed containers to prevent moisture loss and cure at 23°C for at least 24 hours before testing.
Condition the cores in 20°C water for another 48 hours to stabilize their moisture content.
After the initial soak, place the cores in a controlled environmental chamber set to 60°C with a relative humidity of 95% to accelerate potential DEF and conditions are maintained for at least 14 days as DEF typically develops significantly during this period.
Check the dimensions of the cores daily using during this period using digital vernier callipers to monitor any expansion and document any visible signs of distress or cracking.
Calculate the percentage increase in length and diameter from the initial measurements.
Use the expansion data to assess the risk level of residual DEF reactions. Significant expansion (typically more than 0.1% of the original size) indicates highrisk of continued and severe DEF.
Prepare a detailed report documenting the methodology, observations, measurements, and conclusions.
What equipment and expertise are required for Residual Reactivity to Internal Sulphates (RRIS) testing of concrete?
Equipment required for this test includes:
A diamond tipped concrete core drill for sampling.
- An environmental chamber capable of precisely controlling temperature and humidity levels at 60°C and over 95% relative humidity respectively.
Proficiency in structural engineering principles is essential for the development of coring schedules, safe and efficient core extraction, and sample evaluation. Knowledge of materials science or concrete technology is crucial for preparing and conditioning the samples, as well as for executing environmental control during testing. Skill in data analysis is required to accurately interpret expansion measurements and assess potential damage risks. Additionally, the ability to compile detailed reports that document methodologies, results, and recommendations is vital for communicating findings effectively.
What are the advantages of RRIS testing of concrete?
This test evaluates not only existing damage within concrete structures but also measures the potential for future deterioration allowing for a more thorough understanding of the concrete's condition. This information is essential for planning long-term maintenance and repair strategies.
RRIS testing helps in monitoring and mitigating expansive reactions caused by internal sulphate attack, thereby enhancing the overall durability and service life of the structure. Regular monitoring and appropriate interventions can significantly extend a structure’s operational life.
Scientific proof that little potential exists for further degradation through DEF will allow previously condemned structures to resume safe service and can eliminate significant amounts of superfluous maintenance and repair or replacement of concrete structures.
Understanding the future potential for deterioration enables the implementation of preventative measures that can mitigate the extent or even prevent certain types of damage from occurring.
The test is based on controlled experimental procedures that provide quantitative data, supporting maintenance decisions with scientific evidence rather than assumptions.
While the initial cost for such testing might be significant, the long-term savings from avoiding extensive unnecessary repairs and delayed deterioration can be substantial, representing a smart investment in the lifecycle management of concrete structures.
What are the disadvantages of RRIS testing of concrete?
The test procedures are relatively complex involving sample extraction, preparation, and controlled testing environments, which can be cost-prohibitive.
The need to extract concrete cores for testing is inherently destructive and may require further repair post-testing.
The accuracy of predictions from this test can be affected by the environmental conditions in which the concrete operates, which are not always controllable or perfectly replicable in lab settings.
How accurate is RRIS testing of concrete?
Expansion of concrete samples can be identified that is greater than 0.01mm
What are the limitations of RRIS testing of concrete?
While this is extremely cost effective in the long term, initial costs and time investments are high and could limit the scenarios for its feasible adoption.
Expansion during this test is highly dependent on the physical restraints around the concrete sample or within the structure from which the sample is taken. If the in-situ restraint conditions are not accurately replicated during testing, the test results may not effectively predict actual in-service behaviour. Different parts of a concrete structure may experience varying levels of restraint, which can affect the degree of expansion due to sulphate attack. This variability can lead to inconsistent results and may complicate the interpretation of data for large or complex structures.
Sulphate content can vary within a concrete mix and across different sections of a structure. If the sampled area is not representative of the whole structure, the test results might not provide a complete picture of the risk of sulphate-induced expansion.
There is a lack of standardized methods that are universally accepted for testing sulfate reactivity, which can lead to variations in results and difficulties in comparing data from different studies or laboratories.
Ancillary information
Maturity of test: > 10 years
Qualification & interpretation : Specialised lab
Service disruption: No
Preliminary works: No
Time consumption High (> one day)
Cost High
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