Important indicator of sustainability: durability of concrete

Besides evaluating mechanical properties, a further focus of our tests on concrete is on assessing durability. Durability defines the longevity of concrete or concrete structures under their anticipated conditions of use over their expected service life and is thus an important indicator of the cost-effectiveness and sustainability of building materials.

The methods or criteria applied to evaluate durability include the measurement of the resistance to freeze-thaw and to freeze-thaw with de-icing salt, resistance to carbonation and chloride penetration as well as susceptibility to the alkali silica reaction. Depending on the damage reaction concerned, we use the following procedures to test durability.

Alkali silica reaction

The susceptibility of aggregates and concretes to the alkali silica reaction (ASR) can be determined using the 60°C concrete test according to the alkali guideline of the German Committee for Reinforced Concrete (DAfStb). To this end, we prepare test specimens and store them in an ASR test chamber for 140 days. The linear expansion of the test specimens is measured at regular intervals to detect the formation of high-volume silica gels at an early stage. Apart from using proven methods, we are also developing new, innovative and faster methods for determining the susceptibility of aggregates to ASR.

Resistance to freeze-thaw and freeze-thaw with de-icing salt

Exterior building components exposed to freeze-thaw cycles and de-icing salts must meet high resistance requirements. To assess these, we have our own freeze-thaw chest for simulating freeze-thaw cycles and the use of de-icing salt under realistic conditions.

Chloride migration

Resistance to chloride penetration is a highly important parameter, especially where reinforced concretes are concerned, because penetrating chloride ions can cause the reinforcing materials to corrode. Through the tests we carry out in our laboratory, we can provide you with information that will serve to optimally protect the materials you use to reinforce your concrete.

Carbonation

Concrete continuously absorbs carbon dioxide from the atmosphere and assimilates it into its structure. However, in addition to the positive effects of carbon fixation as well as the increase in strength, this process also leads to a lower pH value in the hardened cement paste and thus to a higher risk of reinforced concrete corroding. Our scientists can measure the depth of carbonation in concrete samples and improve your concrete formulation to minimize carbonation.

Shrinkage during the drying process

When concrete dries out during or after it hardens, it can shrink. This is a major disadvantage, not only because of the loss of volume but also because of cracks forming in the building component. However, this can be effectively prevented with a suitable combination of cement and admixtures. Get in touch with us!