Strain development of high strength grouts under compressive fatigue loading and determination of fatigue properties from self-heating measurements

Fatigue behaviour in concrete and grout has become a very important mechanical behaviour to be studied further due to more sleek structures requiring higher performances and strength, such as onshore and offshore wind turbines. However, relatively few studies are available about fatigue behaviour and often contradictory. A series of monotonic and fatigue tests were performed to investigate the fatigue behaviour of ultrahigh strength grout under compression. Multiple stress levels were tested at two loading frequencies, 10Hz and 1Hz. The developments of strain and stiffness degradation were analysed for each test and show a typical three-step damage mechanism. At a higher frequency, some heating is observed within the specimen and the observations are made with thermocouples and infrared thermography. Since the fatigue testing is very time consuming, mostly when defining the S-N curve and endurance limit, an alternative method such as the selfheating method was used. This method is widely applied in materials such as steel [1], aluminium, composite materials or rubber-like materials, to define the endurance limit with only a few specimens based on the heating released during fatigue testing. To the authors knowledge, it has never been used in grout materials. Our experimental work on numerous specimens shows that the self-heating method might be an alternative method in order to predict the endurance limit for concrete and grouts. Erisa Myrtja, Olivier Rateau, Jerome Soudier, Evelyne Prat and Mohend Chaouche