REINFORCED CONCRETE STRENGTHENED WITH CNT
The disasters whether man made or natural ,dominates all types of structures and has an ever been attention to researchers, academicians and scientists. Concrete had been reinforced with steel, macro fibres and micro fibres which bridge the cracks. The advantages of microfibres was to delay the development of micro cracks. How ever their initiation could never be avoided. Numerous researches focus on arresting the initiation of micro cracks. It is quite fruitful and needy for a present scenario to carry out research by reinforcing concrete with fibres at nanoscale which would pave the way for development of crack free material. Nanotechnology is an enabling technology that allows us to develop materials with improved and totally new properties.
CNTs are the subject of one of the most important areas of research in nanotechnology. The reinforced concrete when impregnated with CNTs makes the possibility of arresting the cracks at nanoscale. There should be more focus on applications of REINFORCED CONCRETE IMPREGNATED WITH CARBON NANO TUBES (Single Walled CNTs and Multi Walled CNTs) experimentally on full scale models. The behaviour of concrete will be a challenge when it is reinforced/impregnated with CNTs. The peculiar behaviour must be studied and substantiated by using Finite Element Analysis Softwares.
Concrete can stand for centuries if impregnated with CNTs.
Carbon Nano Tubes are relatively new material and have gained much recent attention. CNTs are a form of carbon that was first discovered in 1952 in Russia (and mostly ignored) and rediscovered in the 1990's in Japan. They are cylindrical in shape and their name comes from their nano diameter. They can be several millimeters in length and can have one "layer" or wall (Single Walled nanotube) or more than one wall (Multiwalled nanotube).
The cost of CNTs may come down in future leading to have wide applications in concrete. To have concrete with exceptional qualities like multifunctional, ductile ,high strength and crack free concrete, CNTs are essential. The tensile strength of CNTs as reported by Scientists is about 2 to 5 Gpa and upto 20 Gpa and the Young's modulus of Elasticity is more than 1.8 TPa. Nanotubes make concrete impenetrable to water, salt etc., adding centuries to the useful life. This can greatly increase the durability of concrete. The production cost of nanotubes is relatively high as the price ranges from Rs.1200 to Rs.65000 per gram in Indian Context.
Scope for Research works on applying CNTs to construction industry and the challenges awaiting.
Various researchers have done studies on the addition of CNTs (and quantified their percentages) with that of the cementitious materials as well as the matrix there by optimizing the percentage with and with out plasticizers. The optimal range stands to be hardly around 2%. However there still exists unanswered questions regarding two main problems as stated by European Scientists. The CNTs form a bundle by clamping together and aslo there is a lack of cohesion between them and matrix bulk material.
Du to interaction between the Graphene sheets of the nanotubes , the tubes tend to form aggregates or ropes. The ropes entangle so that uniform dispersion is affected. This area could be focused so that disentangling the ropes from uniform dispersion could be arrived.
Hence the major problem is the proper adhesion between CNT and the matrix. This has been so far done by various techniques such as pre dispersing CNTs in (a) Water with Gum Arabic (b) Dispersion in Sulphuric Acid ( Sulfuric Acid ) (c) Dispersion in Ethanol and Sonication.
So there could be research focussing the optimal values of CNTs and dispersing agents in the mix design parameters.
So far the studies have focused on quoting down the procedures for mixing the CNTs in powder form and their optimal values. It has been even concluded that the CNTs can be woven and cords can be obtained in the laboratory leading to microstructure.. These cords are flexible and have huge tensile strength and find their applications in pretensioning and post tensioning structures as well as in Suspension cable Bridges. An extensive focus may be done on utilizing the macroscopic structures of CNT woven cords as reinforcements.
If were to do research on CNTs, I would focus on quantifying the optimal values of CNTs and dsipersing agents in the mix design parameters and also on utilizing the CNTS woven cords as reinforcements in Concrete. I would prefer the research entitled
" Study on behaviour of Reinforced Concrete Elements Strengthened with CNTs"
The major hindrance in implementing nanotechnology for research in Civil Engineering Field is insufficient funds as the cost is huge. The survey reports from Europeans say that only 28 % have answered that they have got sufficient funds for the research and rest have been denied. The technical drawbacks reported that cost or more accurately cost -to - benefit is the major concern as the Carbon Nanotubes as priced at the moment 20 Euros to 1000 Euros per gram depending on the quality. This is incompatible with the concrete industry wher the production is accounted as 12 Billion Tonnes/Year.
Hence if the construction industry focuses on utilization of CNTs , the manufacturing cost may come down. In our country, various units for synthesising CNTs can be installed for the production so that industrialization and commercialization will benefit the applications to the fullest extent.