RE: NANO CONCRETE
NANO CONCRETE. HIJAS. mes.docx (Size: 1.4 MB / Downloads: 97)
Nano concrete is one of the most active research areas that encompass a number of disciplines including civil engineering and construction materials.Currently, the most active research areas dealing with cement and concrete are: understanding of the hydration of cement particles and the use of nano-size ingredients such as titanium oxide, silica, carbon nano tubes, and nano- sensors. If cement with nano-size particles can be manufactured and processed, it will open up a large number of opportunities in the field of ceramics, high strength composites etc. it will elevate the status of Portland cement to a high tech material in addition to its current status of most widely used construction material. The main objective of this paper is to outline some of the applications of nanotechnology in concrete and comparing this concrete with the ordinary concrete
Nano technology is actually one of the most active research areas. It made a greatbreakthrough in the history of civil engineering, especially in the concrete world. It is being used for the creation of new materials, devices and systems at molecular, nano- and micro-level. A long time used material m concrete is for the first time fully replaced by a nano material. It is well known m physics and chemistry that a well designed and developed nano material produces better and cheaper cost results than traditional materials. Micro silica has been one of the world's most widely used products for concrete for over eighty years. Its properties allowed high compressive strength concretes; water and chemical resistant concretes, and they have been part of many concrete buildings that we see nowadays. Its disadvantage, though, has been its relatively high cost and contamination, which affects the environment and the operators' health. As micro silica, as a powder, is thousand fold thinner than cigarette smoke. Operators must take special precautions to avoid inhaling micro silica and not to acquire silicosis, an irreversible disease. Hence to overcome all tease above ill-effects of micro silica, nanotechnology was introduced in the world of concrete.The following section describes some of the most promising applications of nanotechnology in concrete technology that are being developed or are even available today.
CONCEPT OF CONCRETE
Concrete is a composite construction material, which is prepared by mixing cement (commonly Portland cement), other cementatious materials such as aggregate (generally a coarse aggregate made of gravel or crushed rocks, plus a fine aggregate such as sand), water and chemical admixtures. When all this components are mixed in a proper proportion, it will set, and harden, to give a strong and durable product.The word concrete comes from the Latin word "concretus" (meaning compact or condensed).Concrete solidifies and hardens after mixing with water and placement due to a chemical process known as hydration. The water reacts with the cement, which bonds the other components together, eventually creating a robust stone-like material. Concrete is used to make pavements, pipe, architectural structures, foundations, motorways/roads, bridges/overpasses, parking structures, brick walls, and footings for gates, fences and poles.
Concrete has relatively high compressive strength, but much lower tensile strength. For this reason is usually reinforced with materials that are strong in tension (often steel). The elasticity of concrete is relatively constant at low stress levels but starts decreasing at higher stress levels as matrix cracking develop. Concrete has a very low coefficient of thermal expansion and shrinks as it matures.The typical specifications for commonly used concrete mix are -Strength 20 MPa,-Aggregate size 20 mm,-Slump 80 mm.We should be aware of the considerations involved in designing strong, durable, high quality concrete.Concrete can be damaged by many processes, such as the expansion of corrosion products of the steel reinforcement bars, freezing of trapped water, fire or radiant heat, aggregate expansion, sea water effects, bacterial corrosion, leaching, erosion by fast-flowing water, physical damage and chemical damage (from carbonation, chlorides, sulfates and distillate water). All concrete structures will crack to some extent, due to shrinkage and tension. Concrete that is subjected to long-duration forces is prone to creep.Concrete is one of the most durable building materials. It provides superior fire resistance, compared with wooden construction and can gain strength over time. Structures made of concrete can have a long service life. Concrete is the most widely used construction material in the world with annual consumption estimated at between 21 and 31 billion tones. But this concrete has some disadvantages also.The cement industry is one of two primary producers of carbon dioxide (CO2).
NANO TECHNOLOGY AND CONCRETE
Nanotechnology is one of the most active research areas, All over the world, that encompass a number of disciplines including civil engineering and construction materials."Nano technology is the study of the control of matter on an atomic and molecular scale. It deals with the size 100 nanometers or smaller, and involves developing materials or devices within that size".Currently, the most active research areas dealing with cement and concrete are: understanding of the hydration of cement particles and the use of nano-size ingredients such as alumina and silica particles. There are also a limited number of investigations dealing with the manufacture of nano-cement. If cement with nano-size particles can be manufactured and processed, it will open up a large number of opportunities in the fields of ceramics, andhigh strength composites.
ELEMENTS OF NANO CONCRETE
A Nano concrete is almost similar as conventional concrete, except that, some nano sized ingredients make a nano concrete, something special. Following are the important components of nano concrete.
Concrete is the most widely produced manmade material. Micro- silica can be applied to concrete improving its properties or reducing its cement content. Cure Because of its innovation the nano silica was tested for over a year in the world’s largest subterranean copper mine to prove its long term characteristics. Cure concrete takes care of the environment, the concrete and the operators' health. It is the first nano product that replaced the micro silica.Cure concrete surpassed the expectations of its design and gave concrete not only the high initial and final resistance but in addition, plasticity, impermeability, minor final cost of work, and cement savings of up to 40%. Also, it lowered the levels of environmental contamination. Optimal use of nano silica will create a new concrete mixture that will result in longer-lasting buildings, roadways, sidewalks, stairs, sewers, and Dams.
Nano concrete is really a superior product of nano technology, which made a greatbreakthrough in the history of concrete. It posses several advantages over the conventional concrete verities.
Well-dispersed nanoparticles increase the viscosity of the liquid phase, which helps to suspend the cement grains and aggregates, which, in turn, improves the segregation resistance and workability of the system.
Nanoparticles fill the voids between cement grains, which results in immobilization of free water (filler effect).
Well-dispersed nanoparticles act as centers of crystallization of the cement hydrates, which accelerates the hydration.
Nanoparticles improve the structure of the aggregate contact zone, which results in better bond between aggregates and cement paste.