Nanotechnology is the engineering offunctional systems at the molecular scale.
Nanotechnology is concerned with objects between 1 and 100nm in size.( Nano meter)
1 Nanometer – 1 x 10-9m.
Applications of nano technology in civil engineering are numerous. Some of the applications are elaborated below.
Application in concrete:
Addition of nanoscale materials into cement could improve its performance. Use of nano-SiO2 could significantly increase the compressive for concrete, containing large volume fly ash, at early age and improve pore size distribution by filling the pores between large fly ash and cement particles at nanoscale. The dispersion/slurry of amorphous nanosilica is used to improve segregation resistance for self-compacting concrete. It has also been reported that adding small amount of carbonnanotube (1%) by weight could increase both compressive and flexural strength.
Cracking is a major concern for many structures. University of Illinois Urbana-Champaign is working on healing polymers, which include a microencapsulated healing agent and a catalytic chemical trigger. When the microcapsules are broken by a crack, the healing agent is released into the crack and contact with the catalyst. The polymerization happens and bond the crack faces. The selfhealing polymer could be especially applicable to fix the microcracking in bridge piers and columns. But it requires costly epoxy injection.
Application in Steel
Steel is a major construction material. Its properties, such as strength, corrosion resistance, and weld ability, are very important for the design and construction. It is possible to develop new, low carbon, highperformance steel (HPS). The new steel was developed with higher corrosion-resistance and weld ability by incorporating copper nanoparticles from at the steel grain boundaries.
The coatings incorporating certain nanoparticles or nanolayers have been developed for certain purpose. It is one of the major applications of nanotechnology in construction. For example, TiO2 is used to coat glazing because of its sterilizing and anti fouling properties. The TiO2 will break down and disintegrate organic dirt through powerful catalytic reaction. Furthermore, it is hydrophilic, which allow the water to spread evenly over the surface and wash away dirt previously broken down. Other special coatings also have been developed, such as anti-fraffiti, thermal control, energy sawing, antireflection coating.
Sensors have been developed and used in construction to monitor and/or control the environment condition and the materials/structure performance. One advantage of these sensors is their dimension (10 -9m to 10-5m). These sensors could be embedded into the structure during the construction process. Smart aggregate, a low cost piezoceramic-based multi-functional device, has been applied to monitor early age concrete properties such as moisture, temperature, relative humidity and early age strength development. The sensors can also be used to monitor concrete corrosion and cracking. The smart aggregate can also be used for structure health monitoring. The disclosed system can monitor internal stresses, cracks and other physical forces in the structures during the structures’ life. It is capable of providing an early indication of the health of the structure before a failure of the structure can occur.