Following emerging nanotechnology applications in bio-medical and electronic industries, the construction industry recently started seeking out a way to advance conventional construction materials using a variety of manufactured nano materials.
Use of nanotechnology materials and applications in the construction industry should be considered not only for enhancing material properties and functions but also in the context of energy conservation, reports Michael Berger on Nanowerk.
This is a particularly important prospect since a high percentage of all energy used, like 41% in the USA, is consumed by commercial buildings and residential houses by applications such as heating, lighting, and air conditioning.
Rice University has looked at the benefits of using nano materials in construction materials but also highlights the potentially harmful aspects of releasing nano materials into the environment.
Prof Pedro J Alvarez, an engineer at Rice University, led a team to compile a list of current use of nano materials in various building applications and also highlighted potential and promising future uses.
* Carbon nano tubes offer mechanical durability and crack prevention in cement, enhanced mechanical and thermal properties in ceramics; real time structural health monitoring (NEMS /MEMS), and effective electron mediation in solar cells.
* Silicon dioxide nano particles (SiO2) are used in reinforcement in mechanical strength in concrete; coolant, light transmission, and fire resistance in ceramics; flame proofing and anti reflection in window glass.
* Titanium dioxide nano particles (TiO2) offer rapid hydration, increased degree of hydration, and self-cleaning in concrete; super hydrophilicity, anti-fogging, and fouling-resistance in window galss; non-utility electricity generation in solar cells.
* Iron oxide nanoparticles (Fe2O3) increase compressive strength and abrasion-resistant in concrete.
* Copper nano particles offer weldability, corrosion resistance, and formability in steel.
* Silver nano particles offer biocidal activity in coatings and paints.
* Quantum dots offer effective electron mediation in solar cells.
Nano SHEQ risks
Manufactured nano materials, in particular synthesized nano particles and carbon nano tubes, may be accidentally or incidentally released to the environment at different stages of their life cycle.
Some manufactured nano materials could be considered as emerging pollutants because their environmental release is not yet regulated.
Once in the environment, manufactured nano materials may undergo diverse physical, chemical, and biological transformations that change their properties, impact, and fate.
Holistic nanomaterials lifecycle exposure profiling is essential to evaluate and manage potential impacts to human and ecosystem health.
Risk factors range from occupational exposure of workers during during coating, molding, compounding, and incorporation of nano materials into the finished building materials or components, to community exposure to community exposure during construction, repair, renovation, and (mainly) demolition activities.
At the end of the life cycle, there is a risk of environmental release from solid nano material wastes as they get disposed of in landfills and incinerators.
Aerosolisation of manufactured nano materials, waste water effluents from manufacturing processes, and construction work, as well as adhesive wear, abrasion, and corrosion of buildings/civil infrastructures could also result in manufactured nano materials’ release to the environment.
Nano SHEQ management
“Whether nano-enabled construction materials could be designed to be “safe” and still display the properties that make them useful is an outstanding question” the authors state. Adopting principles of industrial ecology and pollution prevention could be a high priority to prevent environmental pollution and associated impacts by manufactured nano materials.
Some substances can be re-engineered to create safer, greener, and yet effective products. Recent examples include the substitution of branched alkyl benzene sulfonate detergents, which caused excessive foaming in the environment, with biodegradable linear homologues, as well as the replacement of ozone-depleting chlorofluorocarbons by less harmful and less persistent hydro chloro fluoro carbons.
It is important to discern the molecular structures and associated properties that make nano materials harmful and determine which receptors might be at higher risks. However, detoxification could result in loss of useful reactivity, and focusing on exposure control, as by using appropriate durable coatings during manufacturing, improving matrix stability to minimise manufactured nano materials leaching, and adopting controlled construction and careful disposal practices, rather than suppressing intrinsic reactivity that contributes to toxicity might be appropriate in many cases.
Nano materials are mainly use in energy conservation applications, like solar panels, insulation, and self-cleaning nano-TiO2-coated surfaces.
Additional opportunities include the use of quantum dots and carbon nano tubes to improve the efficiency of energy transmission, lighting, and/or heating devices, as well as incorporation of fullerenes and graphene to enhance energy storage systems such as batteries and capacitors that harvest energy from intermittent, renewable sources like solar and wind.
Some nano materials extend the durability of structures by enhanced resistance to corrosion, fatigue, wear, and abrasion) also contribute indirectly to saving energy that would otherwise be used to repair or replace deteriorated infrastructure.
Some of the new materials substitute materials that can become harmful environmental pollutants, such as lead and mercury.
PHOTO; Carbon nanotubes of four types, used in concrete, ceramics, composites, or coatings.