Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Crack Formation in Concrete

30.08.2007
Cracks in concrete structure elements can strongly prejudice their function and aesthetic appearance. Cracks cannot usually be avoided but their number and size can be controlled and it is technically feasible to close the cracks that form in many cases.

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.-Ing. Hans-Carsten Kühne
Head of Working Group "Cementitious materials:
advanced performance "
Division VII.1 Building Materials
Phone: +49 30 8104-3229
Email: hans-carsten.kuehne@bam.de

Dr. Ulrike Rockland | idw
Further information:
http://www.bam.de

More articles from Materials Sciences:

nachricht Graphene origami as a mechanically tunable plasmonic structure for infrared detection
25.04.2018 | University of Illinois College of Engineering

nachricht Scientists create innovative new 'green' concrete using graphene
24.04.2018 | University of Exeter

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Getting electrons to move in a semiconductor

25.04.2018 | Physics and Astronomy

Reconstructing what makes us tick

25.04.2018 | Physics and Astronomy

Cheap 3-D printer can produce self-folding materials

25.04.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>