Self-compacting high-performance concrete (SCHPC) has till now suffered from one weakness: when exposed to fire it flakes and splits, which reduces its loadbearing capacity. Empa scientists have now developed a method of manufacturing fire-resistant self-compacting high-performance concrete which maintains its mechanical integrity under these conditions.
Wood crackles as it burns in a chimney or campfire. When concrete is exposed to fire it chips and flakes – a process known as spalling. Both effects are due to the same phenomenon: water trapped within the piece of wood or concrete element vaporizes due to the high temperature. As more water vapour is produced the pressure within the wood or concrete structure increases. In wood this causes the cells to burst with a crackling sound, creating cracks in the logs. In concrete structures, chips split away from ceilings, walls, and supporting pillars, reducing their loadbearing capacity and increasing the risk of collapse in a burning building.
The resistance of conventional vibrated concrete to the heat of a fire can be optimized by adding a few kilograms of polypropylene (PP) fiber per cubic meter of concrete mixture. When exposed to fire the fibers melt, creating a network of fine canals throughout the concrete structure. These allow the water vapour to escape without increasing the internal pressure, so the concrete structure remains intact.
A trio of researchers with Northwestern University has created a type of concrete made only from materials found on Mars, which suggests it could be used as a building material for those who make the journey to the Red planet sometime in the distant future. The trio, Lin Wan, Roman Wendner and Gianluca Cusatis, have written a paper describing their efforts and results and have posted it on the preprint server arXiv.
Many countries and consortiums have been looking into the possibility of not only sending humans to Mars, but of establishing a presence there—perhaps even building a permanent colony. But there are many obstacles that must be overcome first, one of which is figuring out how to build a place to live on the planet without having to carry the materials for it—a tricky problem when noting the barren terrain. In this new effort, the research trio looked into the possibility of making concrete out of only material available on Mars, and notably, without the need for water, which is always used to make concrete here on Earth.
A fine ash, made from pulverised volcanic rocks, can be added to traditional cement to improve its sustainability.
Who is involved?
MIT engineers working with scientists from the Kuwait Institute for Scientific Research and Kuwait University. The paper, Impact of Embodied Energy on materials/buildings with partial replacement of ordinary Portland Cement (OPC) by natural Pozzolanic Volcanic Ash, can be viewed here bit.ly/2EwZQwr
How is it novel?
By replacing a percentage of traditional cement materials with volcanic ash, researchers reduced the total energy required to make concrete. Building 26 concrete buildings, using cement with 50% volcanic ash, required 16% less energy than if traditional Portland cement was use, according to calculations.
The researchers also found that concrete mixed with a very fine ash was stronger than concrete made from just Portland cement. However, the process of pulverising volcanic ash to a very fine particle size requires energy. Therefore, if stronger concrete is made using this method, it becomes less sustainable in terms of energy use.
Oral Buyukozturk, a professor in MIT’s Department of Civil and Environmental Engineering, commented, ‘You can customise this. If it is for a traffic block, for example, where you may not need as much strength as, say, for a high-rise building. So you could produce those things with much less energy. That is huge if you think of the amount of concrete that’s used over the world.’
Nanyang Technological University (NTU Singapore) scientists from the NTU-JTC Industrial Infrastructure Innovation Centre (I³C) have invented a new type of concrete called ConFlexPave that is bendable yet stronger and longer lasting than regular concrete which is heavy, brittle and breaks under tension.
This innovation allows the creation of slim precast pavement slabs for quick installation, thus halving the time needed for road works and new pavements. It is also more sustainable, requiring less maintenance.
NTU Professor Chu Jian, Interim Co-Director of the NTU-JTC I³C, said, “We developed a new type of concrete that can greatly reduce the thickness and weight of precast pavement slabs, hence enabling speedy plug-and-play installation, where new concrete slabs prepared off-site can easily replace worn out ones.”
Mr Koh Chwee, Director, Technical Services Division of JTC and Co-Director of the NTU-JTC I3C, said that the invention of this game-changing technology will not only enable the construction industry to reduce labour intensive on-site work, enhance workers’ safety and reduce construction time, it also benefits road users by cutting down the inconvenience caused by road resurfacing and construction works.
Researchers at Binghamton and Rutgers Universities, USA, have developed a self-healing fungi concrete mix that could help solve the issue of crumbling infrastructure – caused by cracks in the structure’s concrete. The team received support from the Research Foundation for the State University of New York’s Sustainable Community Transdisciplinary Area of Excellence Program.
Assistant Professor Congrui Jin, Binghamton University, commented, ‘Without proper treatment, cracks tend to progress further and eventually require costly repair […] If micro-cracks expand and reach the steel reinforcement, not only the concrete will be attacked, but also the reinforcement will be corroded, as it is exposed to water, oxygen, possibly CO2 and chlorides, leading to structural failure.’
The team found that mixing Trichoderma reesei – a fungus – with the concrete could solve this issue. The fungus lies dormant in the mix until water and oxygen reach it through cracks in the concrete.
‘With enough water and oxygen, the dormant fungal spores will germinate, grow and precipitate calcium carbonate to heal the cracks,’ commented Jin. ‘When the cracks are completely filled and ultimately no more water or oxygen can enter inside, the fungi will again form spores. As the environmental conditions become favorable in later stages, the spores could be wakened again.’
Further research is needed to ensure the fungus can survive in the concrete mix.
To find out more on materials science, packaging and engineering news, visit our website IOM3 at or follow us on Twitter @MaterialsWorld for regular news updates.
