Posts Tagged Concrete
Glass | A Versatile Building Material
Posted by Architect in Architecture & Civil Engineering on June 16, 2010
Glass has become a much-used material in interior as well as exterior architecture. In earlier times, glass used to be fragile, and had very limited application. But this view has undergone a drastic change now. Glass is an excellent material available in toughened form and is a very important element in the arsenal of Architects and Interior Designers.
The cuteness of glass lies in its ability to provide a variety of innovative solutions for interior and exterior decoration. The strength of glass for structural purposes has improved tremendously in the past few years, giving Architects a free had in using glass in a very creative way. Interior designers have also made extensive application of this splendid material, which ca be seen on counter-tops, doors, walls, partitions, etc
A new genre of Glass Designers have sprung up, and the versatility of glass has made it possible to create anything, from transparent staircases, to coloured shelves in showrooms, designer ceilings and translucent floorings. And this glass isn’t fragile at all. It is strong and Beautiful.
Glass has made a HUGE impact on the designing industry. We can increasingly see use of sand-blasted glass panels, glass bricks and etched glass in World-Class projects. New varieties of glass like smoked glass, wire glass, frosted glass and Pyrex glass have been developed to aid designers, and are being used in a number of creative ways to enhance the aesthetic beauty of the space. Decorative etched coloured glass and crystals have been traditionally used in interiors.
The use of coloured glass can be traced back to Victorian architecture and Gothic Cathedrals. Today, glass is considered as an important element in the superfluity of available construction materials.
An up-and-coming construction material, Glass Blocks, have become increasingly popular for interior and exterior decoration purposes. They are an excellent material for acoustic & thermal insulation, water-proofing, energy conservation and abrasion resistance. Being a bad conductor of heat gives the use of glass a new practical application in the form of energy-conservation, which makes glass more dulcifying.
With their improved strength, pressure and impact resistance, heat and water-proof characteristics, glass blocks can be used either to construct the walls separately, or used freely for decorative purposes.
Glass blocks can be shifted and collocated freely with other shapes or colours to meet various demands of different applications. Transparent glass blocks can be used for interior divisions as they have an excellent lighting performance and seem to extend the available space.
This fascination with glass and mirrors began in the early 19th century when Architect Sir John Soane adored the mirrors, and the space-expanding effect they had in the interiors.
Today, glass is used all over the world. A designer’s pursuit for transparency, weightlessness and luminosity has been fulfilled by Glass. Most major projects around the world use glass in some way to add beauty to buildings and create astounding pieces of art. Glass is taking the world of architecture and interiors by storm.
Using Fibers as Concrete Admixtures
Posted by Architect in Architecture & Civil Engineering on June 16, 2010
Admixtures are materials other than cement, aggregate and water that are added to concrete either before or during its mixing to alter its properties, such as workability, curing temperature range, set time or color. Addition of fibre to concrete makes it tough and fatigue resistant. Such type of admixtures are used extensively in important engineering projects.
Fibre reinforcement of cement and concrete is not really a new concept since we have been using reinforcements like straw in bricks and hair in mortar for a long time. However, there has been a lot of research and development in this area during the last two decades.
Addition of fibre to concrete is a convenient and practical method of improving several properties of the material, for example, toughness, fatigue resistance, impact resistance and flexural strength. It also assists in changing the flow characteristics of the material.
Concrete with fibre reinforcement differs from conventional concrete in several respects. It has higher cement content, lower coarse aggregate and a smaller size of aggregate.
Generally, the fibre content varies from 0.2% to 2%.
Types of Fibres
There are several types of fibres, including steel, alkali-resistant glass and polyethylene.
Fibres can be divided into two types, viz, those with moduli lower than the cement matrix, such as cellulose, nylon and polypropylene, and those with higher moduli, such as asbestos.
Organic Fibres with lower modulus are generally subjected to high creep, which means that if they are used to support permanent high stresses in a cracked composite, considerable elongations or deflections may occur over a period of time.
The intercellular substance or matrix used is important because each has a different degree of alkalinity which affects the durability of glass and steel fibres.
The maximum particle size is also important as it affects the fibre distribution and the quantity of fibres. Concrete should have particles not more than 10mm in size, otherwise it becomes difficult to achieve uniform fibre distribution.
The use of new materials and modern techniques is important in construction activities. Proper use of different kinds of materials and the latest technology becomes imperative to improve quality and cut costs. The life and durability of structure also increases.
Several different types of modern construction materials include blended cements, micro-silicas, fibres for reinforcement, chemicals like epoxy and geo-textiles. Also used are plastics, aluminium prefabricated concrete products, and different cladding materials in walls, doors and windows.
The use of prefabricated concrete has become a common practice in the construction of bridges and flyovers in India. In addition, addictives, curing compounds and steam curing have been used successfully in highways and railways projects in India to ensure fast completion.
The use of new materials like epoxy, polymers, micro-silicas and fibre-reinforced cement mortars has also improved the quality of construction. The use of fibres improves its shear strength and torsional strength, besides improving the energy absorbance, resistance to wear, freeze and thaw damage, friction and skid resistance and durability.
Mineral Admixtures
Availability of mineral admixtures marked the opening of a new era for designing concrete mix of higher and higher strengths. However, it was experienced, and hence realized, over a period of time, that it was not only the strength that was important, but also other properties like durability and workability were also vital performance parameters. This has led to research on high performance concrete (HPC). HPC mix is designed with mineral and chemical admixtures along with normal ingredients of concrete, having low water-cementitious ratio.
Mineral admixtures are added to concrete in relatively varying quantities, generally 5% to 40% by weight of cement. Addition of mineral admixtures to concrete reduces heat of hydration due to reduced cement content and increases durability by contributing to pore refinement.
Kaolin is a reactive type of mineral admixture, and has been traditionally used for the manufacture of porcelain. Metakaolin is a sub-type of kaolin which is used in the construction industry.
Applications of Metakaolin
* High performance, High strength and Lightweight concrete
* Precast Concrete for architectural, Civil, Industrial and structural works
* Fibercement and Ferrocement products, Glass Fiber Reinforced Concrete.
* Mortars, Stuccos, Repair Material, Pool plasters.
* Manufactured Repetitive Concrete products
Metakaolin can be used in mortars and concrete for:
* Increased Compressive and Flexural Strengths
* Reduced Permeability & Efflorescence
* Increased resistance to Chemical attacks
* Prevention of ASR
* Reduced Shrinkage
* Improved finishability, colour and appearance.
Conclusion
Metalaolin has a great potential in concrete as cement replacement at lower cost as compared to traditionally used super pozzolans. Concrete produced with metakaolin shows similar behaviour to that with one produced with silica fume. It is expected that use of Concrete admixtures, like metakaolin will grow very fast in cement, mortars and High Performance Concrete.