Concrete is an artificial rock produced from cement, aggrgates (sand and gravel or broken stone) and water. It cannot be considered as a material with specified properties as these develop as a function of age and continue changing over time. Cement hardening and drying is usually accompanied by shrinkage, therefore fine cracks are inevitable. Cracks exceeding 0.1 mm can be handled by optimising the concrete composition and by using reinforcement.
Crack formation caused by dynamic and static stress on concrete structure elements is due to working loads and permanent load. Thermal and chemical impacts and frost-deicing stress in the pore system of the concrete are also important. Suitably designed composition and/or preventive measures (hydrophobic treatment, coating) can long-lasting prevent weathering damages.
Permanent weathering, horizontal surfaces, dark surfaces and sharp edges increase the risk of cracking formation and/or flaking due to increased thermal strain and unfavourable stresses in the building component. Avoiding cracks greater than 0.1 mm is often planned in the design phase for technical reasons (e.g. waterproof concrete). This may also be necessary on aesthetic causes.
Before filling the cracks an appraisal has to be made to specify necessity, objectives and methods. Two techniques are applicable in principle to fill the cracks: soaking (filling the cracks without applying pressure) or injection (filling the cracks under pressure). Epoxy resins, polyurethane, cement paste or cement grouts are usually used for this purpose. The Guidelines of Concrete Repair of the German Committee for Reinforced Concrete of 2001 and/or DIN EN 1504 Part 5 and 9 regulate the relevant technical aspects.Contact:
Dr. Ulrike Rockland | idw
Siberian scientists suggested a new method for synthesizing a promising magnetic material
23.01.2018 | Siberian Federal University
Complex tessellations, extraordinary materials
23.01.2018 | Technische Universität München
Physicists have developed a technique based on optical microscopy that can be used to create images of atoms on the nanoscale. In particular, the new method allows the imaging of quantum dots in a semiconductor chip. Together with colleagues from the University of Bochum, scientists from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute reported the findings in the journal Nature Photonics.
Microscopes allow us to see structures that are otherwise invisible to the human eye. However, conventional optical microscopes cannot be used to image...
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
23.01.2018 | Life Sciences
23.01.2018 | Earth Sciences
23.01.2018 | Physics and Astronomy