Chandigarh, Thursday, October 22, 1998
world of admixtures
Super-cold particle holds
Enter the world
NOT a single drop of water will enter your house even in torrential rains. That is the new commitment made by water-proofing compounds that have recently been developed by the construction chemicals industry. Be it a basement or a swimming pool, a terrace garden or the sunken roof of a bathroom, all can be given a foolproof treatment against any kind of dampness. Not only this, even efflorescence and saltpetre action cab be taken care of. Chemical injection grouting for rapid grouting of foundation bolts of heavy machinery with high vibratory loads and chemical DPC treatment against rising dampness in a building that has already been erected may ensure that the building that was likely to be abandoned, lasts a life time now. A rapid development in construction chemicals and admixtures has opened new possibilities of saving old buildings as well as making new buildings damp proof, impervious and efflorescence free.
Water-proofing is not the only area covered by the construction chemicals developed now but providing protective coatings to floors against abrasion and chemical action, creating water repelling barriers and sealing all types of cracks in sanitary ware, plumbing joints, tiles, stone ware joints, walls and roofs can also be achieved by use of these admixtures. Wall and floor tiles are more and more in demand than ever. The tile adhesives available now can provide best adhesion & mortar workability, making the job of tile fixing much easier, spot free, full of strength and durability.
A notable achievement of these admixtures is that their use can bring an enhancement in quality of construction itself. Two most important aspects of an admixture to be added to concrete or mortar are that the admixture must be chloride free and compatible with the cement under use. There should not be any adverse chemical reaction among the cement and the admixture. The admixtures developed now to act as accelerators, retarders, plasticisers, super plasticisers and air entraining agents fully meet with these two requirements. There are other aspects such as non shrinking quality of admixtures and higher workability and these too are well served by the array of concrete admixtures developed by Indian chemical industry.
To avoid confusion or incorrect use of construction chemicals and admixtures, these can be classified into five categories as concrete admixtures, water-proofing compounds, protective coatings, adhesives and sealants. Under each category, these compounds can further be classified on the basis of their base material and best possible use. A manufacturer may suggest his item as a master-product suitable for use under all conditions and circumstances but one product may certainly have a better specific use than the other and this classification of chemicals and admixtures may serve as a ready-reckoner to have a better choice.
Concrete admixtures can be best classified as plasticisers, super plasticisers, accelerators, retarders and air-entrainers. These admixtures are added to concrete during its preparation and before its placement in position. These admixtures may bring durability, strength enhancement, workability, corrosion protection and flexural strength to concrete. The choice depends upon the objective to be achieved. These ad- mixtures facilitate construction and save cement besides enhancing physical properties of concrete. The air entrainers provide remarkable frost resistance property to concrete.
Dampness in buildings, Efflorescence on walls or saltpetre problem are of common occurrence in buildings. The basis cause of all these is a rising dampness from foundations, presence of humidity in walls or a leak or water passage in the roof. The nitrates, chlorides and sulphates present in the walls come out along with moisture and appear on the wall surface as efflorescence making it look ugly & full of stains. The source of moisture has to be located, plugged and at the same time the porosity of walls is to be treated by application of suitable water-proofing coating. Colourless, odourless and water repelling coatings that penetrate deep into the wall should be selected for use. A leakage may not only become a nuisance but damage to the structure may also happen. Right use and application of water proofing admixtures save structural failure also.
A number of protective coatings have now been invented. These surface treatments may save a structure if there had been poor workmanship during construction. Cracks may appear in a structure due to temperature fluctuations. Instead of waiting for the cracks to appear and then applying sealants to them, it will be better to apply protective coatings and to overcome the hidden defects. The protective coatings developed these days are also capable of resisting mild acids, abrasion, algae and ultraviolet rays in addition to providing water-proofing, heat resistance and withstanding thermal expansion and contraction.
Marble, granite, stone slabs and various types of tiles have now become of common use. The adhesives developed recently provide excellent adhesion properties and also render spotfee service. Some of the adhesives are fully effective even if used in damp conditions. Among sealants, the polysulphide sealants carry remarkable sealing characteristics. These have come under wide use in airports, dams, reservoirs, atomic power stations, bridges, sub-ways and buildings. Their tensile adhesion, peel adhesion, ultraviolet resistance and water resistance have touched excellent levels. Silicon sealants have proved highly useful in structural glazing, curtain walls, automobile and coach building. Any joint or crack can be sealed for a 10 year service or more by use of these sealants.
construction chemical industry has developed very fast in
the last few years aiming at a synthesis of chemistry and
construction. Ask any house owner, hotel manager,
maintenance engineer or building care-taker, the major
problems faced by him are leakages, dampness, cracks and
efflorescence. Right use of admixtures can help in saying
goodbye to these problems for ever.
Super-cold particle holds secrets
FOR a few seconds last month the coldest spot in the universe was in Brighton, a seaside town on the south coast of England. While the temperature outside hovered around 20°C on September 22, inside Malcolm Boshiers optics lab at Sussex University it was a few hundred billionths of a degree above the coldest temperature possible, -273°C.
When Boshier and his team dropped 100,000 atoms down to nanokelvin temperatures, they were not merely trying to get into the Guinness Book of Records. This is a step on the road to making the worlds most sensitive measuring instruments, so sensitive they might help to unlock the secrets of gravity.
The big freeze created a Bose-Einstein Condensate (BEC) which occurs when atoms lose almost all their energy. In this state an extraordinary thing happens: each atom loses its individuality. They spread out into each other, forming a blob that behaves like one enormous superatom. Its an object that obeys the laws of quantum mechanics, yet its large enough that you can take a picture of it, says Boshier.
Albert Einstein and Satyendra Bose predicted such a thing would happen at ultra-low temperatures more than 70 years ago, but it wasnt until 1995 that a Colorado research group first made a BEC. This represents the tightest control you can have over atoms, says Boshier. We should be able to build devices that will be extremely sensitive to anything that affects an atoms energy levels and that includes gravity. An understanding of just how gravity works still eludes researchers, and an instrument to measure its subtle effects will be vital in unearthing its secrets. The next stage is about to begin. Sussexs Centre for Optical and Atomic Physics has already produced magnetic mirrors, which bounce atoms around in the same way that mirrors bounce laser light. Boshier will soon be dropping the BEC on to a magnetic mirror to check that it bounces like normal atoms.
If it does, the team will try to build an atom interferometer. Lasers provide highly accurate interferometers because the photons the tiny packets of light in their beams are locked in step. This provides a way to measure tiny dimensions. Split a laser beam in two, and the relative length of the two different beam paths can be in one half are slightly out of step with the others. This has led to highly sensitive instruments such as laser gyroscopes.
In a BEC, the atoms, like the photons in a laser beam, are locked together, which will provide an even more accurate interferometer. Creating a BEC involves two stages. First put rubidium vapour into an evacuated flask. Six lasers are arranged around the flask with their beams intersecting at the centre.
To a normal, moving atom this is like wading through what the researchers call optical molasses. The atom loses energy, slows down, and cools to around one thousandth of a degree above absolute zero, or -273°C; cold, but not cold enough.
The lasers are constantly adding energy to the atoms, so they are turned off and a specially-shaped magnetic field is turned on. This holds the atoms as if it were a deep-sided bowl. The atoms with the most energy steal some from the others and escape from the top of this magnetic trap: thus the remaining atoms get colder.
Eventually an atom reaches the point at which it can move into its lowest quantum state: the ground state. The nature of these atoms is such that others quickly follow. When it is cold enough so that there is some chance of having one atom in the ground state, many of the others scatter into that same ground state, says Boshier.
The result is a quantum blob a few microns in diameter. It may not sound like much, but it contains the future, Boshier believes. This field is really exploding: five or six hundred papers most of them theoretical have been written on it in the last three years, he says. This is going to do for atoms what lasers did for light.
By J.P. Garg
1. Russian scientists are soon going to put into the sky what will appear to be a second moon, 10 times brighter than a full moon, above London, Frankfurt and other cities. On which date will this orbiting space mirror quickly pass across the night sky before burning up in the atmosphere? What is the name of this reflecting spacecraft?
2. When completed, GMRT will be the largest telescope of its kind in the world, opening up new vistas in Indian astronomy. What is the complete name of this telescope? Where is it being constructed? Who is the project director?
3. Our Prime Minister recently dedicated to the nation the Kalpakkam Atomic Reprocessing Plant designed to process spent fuel from pressurised heavy water reactors. The processed fuel will be used in a different type of reactor to be set up at Kalpakkam only. What is this latter type of reactor called?
4. A British doctor has recently developed a new technique called MRS. This computerised scanning helps doctors diagnose and analyse brain tumors without biopsy. What does MRS stand for?
5. Indian aerospace scientists are designing a self-fuelling reusable multi-role mini space-plane that can put satellites in orbit and also provide intelligence, surveillance and reconnaissance from space. What has this plane been named?
6. What are the brightest known objects in the universe called?
7. What is the technology called that deals with making intelligent machines which can think like human beings, recognise and respond to sound, and also learn to correct the mistakes committed by them without the help of an operator?
8. Carrots are useful for eyesight, especially to prevent night blindness. Of which vitamin carrots are a rich source? What is the chemical name of this vitamin? Who discovered it?
9. The voice of women and children is normally shriller than that of men. Which characteristic of sound is responsible for this?
10. Genius is one per cent inspiration and ninety nine per cent perspiration. Who said this? Which epithet did he earn? How many patents was he granted?
November 9; Znamya 2.5 2. Giant Metrewave Radio
Telescope; at Khodad near Pune; Prof Govind Swarup 3.
Fast Breeder Reactor 4. Magnetic Resonance Spectroscopy
5. Avatar (Aerobic vehicle for advanced
trans-atmospheric research) 6. Quasi-stellar objects or
Quasars 7. Artificial intelligence 8. vitamin A; retinol;
E.V Mc-Collum and M. Devis 9. Frequency 10. American
inventor Thomas Alva Edison; Wizard of Menlo
Motor cycle- cum-car
BMW has launched a completely new type of vehicle in its City-Mobil CI, recently unveiled in Bonn. Just 2.1 metres long and 98 centimetres wide, it is designed to combine the plus points and eliminate the disadvantages of motor cycle and car. Its constructors concept was a synthesis of the safety and the weather immunity of a modern small car and the manoeuverability of a motor bike, creating a new vehicle specially suited to city traffic. The CI will go on the market in the spring of 2000.
Its main feature is safety. Its safety cell, unaccustomed at first owing to its special crash elements and ingenious frame structure, assures the safety standard of a modern small automobile, including an impact protection zone hitherto thought impossible for two-wheelers. The driver is guarded by two cruciform safety belts ensuring that, even if the CI tips over, his or her head will not strike the ground. Lateral shoulder-height rollbars make sure theres always a wide enough berth to the street. The CI driver is not legally compelled to wear a crash helmet. Crash tests supervised by the federal roads authority impressively documented the CIs safety potential.
But the CI has more to offer than a high safety rating. The vehicle is light and easy to drive, with well arranged controls. Automatic gearshift and electric starter are of modern standard and the CI was praised for its relaxed, upright drivers seat, as well as for its stability, steering and road-holding. Journalists were amazed at the CIs low vulnerability to sidewinds and satisfactory suspension even on rough and bumpy roads.
The CIs engine is still in the development phase. The 125 cc, one-cylinder four-stroke unit is supplied by Bombardier-Rotax of Austria. A digital engine management system is currently being developed for the catalytic convertor, which will be a standard fitting. As for brakes, an anti-block system will be an extra.
Any passenger would have to wear a helmet and have no protection against rain. After all, the CI was conceived as a one-person vehicle, bearing in mind that only the driver occupies 80 per cent of all automobiles on the roads today.
Enhanced coating for dental implants
In a four-year project, scientists at California based Sulzer Calcitek Inc. have designed a new dental implant which combines the advantages of two popular dental configuration designs screw and cylindrical.
Screws form an immediate mechanical interlock with surrounding bone tissue thus securing the implant. But screw implants are difficult to put into the right place by surgical methods as the bone often needs pre-tapping.
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