With suitable analyses we clarify for you:
- Whether the aggregate used is alkali sensitive.
- Whether the concrete of an existing structure has already been damaged by an ASR.
- What consequences result from a damaging ASR.
- What proofs are required by the building authorities?
- We offer you various test procedures for investigating ASR phenomena and thus a wide range of possibilities to answer your questions about ASR.
Petrography involves the identification and classification of rocks as well as their classification according to hazard classes. The result is used to select suitable concrete raw materials.
With the aid of microscopy, our experts examine the damage images in the truest sense of the word. They determine the course of cracks as well as the contact zones between the aggregate and binder matrix by means of stereo, polarisation and scanning electron microscopy (SEM).
The quick test method according to the alkali guideline of the DAfStb:
In the quick test method, mortar samples with the aggregate to be evaluated are stored in caustic soda solution at 80°C for about two weeks to determine the consequences of an ASR based on the elongation of the test specimens.
In our fog chamber, the concrete test specimens are stored for nine months at 40°C and 100% humidity. Afterwards, our specialists assess whether a damaging ASR has occurred based on the degree of expansion and the possible crack pattern.
60°C concrete test
As an alternative to the fog chamber test method, we also offer the concrete test at 60°C above water. This method allows a faster classification of the aggregate into an alkali sensitivity class.
In the performance test, the materials are subjected to climatic storage for 168 to 224 days. During the entire performance test, an alkali is added from outside. In this way, we simulate the "everyday life" of the concrete and can determine the degree of ASR based on the elongation and with the help of microscopic examinations.
As part of the chemical analysis, our professionals determine the alkali content using the Na2O equivalent of the cement. In addition, X-ray diffraction (XRD) and element analyses can be carried out on the scanning electron microscope (SEM) to determine the composition of the ASR gels or other building material components.
We support you in the selection of suitable concrete raw materials to avoid a destructive ASR.
To determine the degree of ASR damage and to initiate countermeasures, we carry out the necessary investigations on existing structures.
To investigate the alkali sensitivity of aggregates we follow the publications of the German Committee for Reinforced Concrete (DAfStb):
DAfStb guideline "Preventive measures against harmful alkali reactions in concrete (Alkali guideline)
DAfStb "Recommendation for the damage diagnosis and repair of concrete structures damaged due to an alkali-silica reaction
Kiwa - Your strong partner for AKR phenomena
With us, the concentrated AKR competence is ready for you.
Our ASR specialists can perform the entire range of tests on-site in Kiwa's own test laboratories. We guarantee you fast, reliable, and highly qualified AKR advice.