Construction
Construction is an area in which nanotechnology can make a big difference. Indeed, some applications are already on the market. For example, in the environment section we look at new smart materials incorporating titanium dioxide nanoparticles that have given rise to self-cleaning windows, buildings and even roads (7000 square metres of road in Milan have been coated with these smart materials, which resulted in a 60% reduction in nitrogen dioxide levels).Other nanomaterials are being incorporated in new construction materials to improve mechanical strength, durability and insulation, while at the same time decreasing the weight compared to traditional materials. For example, ceramic nanoparticles are being used in cement to increase their robustness.
Ambient sensor systems will be increasingly used in construction, to monitor a building’s environment including any mechanical stresses it is placed under.
Nanotechnology and Steel
Steel has been widely available since the second industrial revolution in the late part of the 19th and early part of the 20th Century and has played a major part in the construction industry since that time. The construction industry can
benefit from the application of nanotechnology to steel and some of the promising areas currently under investigation or even available today are explored in the following paragraphs.
Fatigue is a significant issue that can lead to the structural failure of steel subject to cyclicloading, such as in bridges or towers. This can happen at stresses significantly lower than the
yield stress of the material and lead to a significant shortening of useful life of the structure.
The current design philosophy entails one or more of three limiting measures: a design based
on a dramatic reduction in the allowable stress, a shortened allowable service life or the need
for a regular inspection regime. This has a significant impact on the life-cycle costs of
structures and limits the effective use of resources and it is therefore a sustainability as well
as a safety issue.
Current research into the refinement of the cementite phase of steel to a nano-size has
produced stronger cables. High strength steel cables, as well as being used in car tyres, are
used in bridge construction and in pre-cast concrete tensioning and a stronger cable material
would reduce the costs and period of construction, especially in suspension bridges as the
cables are run from end to end of the span. Sustainabilty is also enhanced by the use of higher
cable strength as this leads to a more efficient use of materials.
Research work on vanadium and molybdenum nanoparticles has shown that they
improve the delayed fracture problems associated with high strength bolts in high rise structures. This is the result of the nanoparticles reducing the effects of hydrogen embrittlement and improving the steel micro-structure through reducing the effects of the inter-granular cementite phase.
Nanotechnology and Wood
Wood is an ancient material which has been used since the dawn of civilization. nanotechnology represents a major opportunity for the wood industry to develop new products, substantially reduce processing costs, and open new markets for biobased materials.
Nanotechnology and Glass
The European glazing market, which represents 45% of the worldwide market, reached avolume of 80,000 units in 2001, at a sales volume of €18bn. The current state of the art incladding is an active system which tracks sun, wind and rain in order to control the buildingenvironment and contribute to sustainability, but this is unreliable and difficult to calibrateand maintain. Consequently, there is a lot of research being carried out on the application ofnanotechnology to glass.
Titanium dioxide (TiO2) (box 2, p7) is used in nanoparticle form to coat glazing since it has
sterilizing and anti-fouling properties. The particles catalyze powerful reactions which
breakdown organic pollutants, volatile organic compounds and bacterial membranes. In
addition, TiO2 is hydrophilic (box 4, p9) and this attraction to water forms sheets out of rain
drops which then wash off the dirt particles broken down in the previous process. Glass
incorporating this self cleaning technology is available on the market today.
Fire-protective glass is another application of nanotechnology. This is achieved by using a
clear intumescent layer sandwiched between glass panels (an interlayer) formed of fumed
silica (SiO2) nanoparticles which turns into a rigid and opaque fire shield when heated.
Most of glass in construction is, of course, on the exterior surface of buildings and the control
of light and heat entering through building glazing is a major sustainability issue. Research
into nanotechnological solutions to this centres around four different strategies to block light
and heat coming in through windows. Firstly, thin film coatings are being developed which
are spectrally sensitive surface applications for window glass. These have the potential to
filter out unwanted infrared frequencies of light (which heat up a room) and reduce the heat
gain in buildings, however, these are effectively a passive solution.photochromic
technologies are being studied to react to changes in light intensity by increasing
absorption.electrochromic coatings are being developed that react to changes in
applied voltage by using a tungsten oxide layer; thereby becoming more opaque at the touch
of a button.All these applications are intended to reduce energy use in cooling buildings and
could make a major dent in the huge amounts used in the built environment.
Nanotechnology in Sustainability and the Environment
Sustainability is defined as “the ability to provide for the needs of the world's currentpopulation without damaging the ability of future generations to provide for themselves”. Akey aspect of sustainability is conservation through the efficient use of the resources that aretied up in the already built environment.As existing stock increases so will the need foreffective maintenance and significant benefits will be offered by a realistic assessment ofmaterial lifetimes. Materials scientists have quantitative models which go from nanometres tomillimetres and cover 6 length scales.Engineers have models that go from tenths of millimetres to tens of metres and therefore cover about 6 length scales.Together they can,theoretically, cover 12 scale lengths and a model covering such a scale would be a powerfultool for service life predictions. This is one of the research areas currently under investigationand part of its advancement depends on the development of computing power which itself isdependent on advances in nanotechnology in the electronics field.
Another key aspect of sustainability is the efficient use of energy. In the EU, over 40% of
total energy produced is consumed by buildings. Insulation is an obvious solution to reduce
some of this energy use, however, limited space for installation is a major problem for
building renovation. Micro and nanoporous aerogel (box 8, p17) materials are very good
candidates for being core materials of vacuum insulation panels but they are sensitive to
moisture. This risk is not acceptable for high performance thermal insulation and the next
challenge is to develop a totally airtight wrapping, taking into account the foil and the
welding. As a possible remedy, work by Aspen Aerogels has produced an ultra-thin wall insulation which uses a nanoporous aerogel structure which is hydrophobic (box 4, p9) and
repels water so it is mould free. Another intriguing application of aerogels is silica based
products for transparent insulation, which leads to the possibility of super-insulating windows.
Micro or Nano Electomechanical Systems (MEMS or NEMS) also offer the possibility of
monitoring and controlling the internal environment of buildings (through a potentially
integrated network). This could lead to energy savings much in the way that current motion
detectors switch on light only when needed.
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