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Road Construction and marking equipment |
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INTRODUCTION: In the last one decade, there has been an unprecedented growth in road traffic in India. Suddenly we have lost count of the car Makes. Cargo transport has grown by 60 times during the last fifty years. Passenger traffic has risen by 65 times and number of vehicles by 80 times. Road network, however, has not grown in equal proportion. Though India owns a vast road net-work of 3.3 million kilometers yet it is severely inadequate. National Highways constitute only 1.6% of it. 80% of the road network are village roads and their condition is awful. And this is despite the fact that a host of new methods and machinery have been invented for road construction—the ones that can give stronger, wider and durable roads! The condition of most of the roads in India is deplorable. Pot-holes, deep enough to break the axles of vehicles, stretches washed away by rains and berms poorly maintained, often becoming death-traps for two-wheeler drivers, constitute integral parts of many of our roads and highways. The message is clear: Road construction technology has seen excellent growth but we have not fully adopted the new developments and resigned to whatever conditions of roads are prevalent in the country.. The Pavements : Most of Indian roads are Flexible pavements, the ones having asphalt-toppings. These days, some switch-over to Rigid pavements that is concrete roads is being seen. Each type of pavements has its own advantages and disadvantages. Flexible pavements have a great advantage that these can be strengthened and improved in stages with the growth of traffic. Another major advantage of these roads is that their surfaces can be milled and recycled. These are less expensive also. Concrete roads on the other hand offer better skid resistance, need lesser maintenance, allow better vehicle-mileage to road users and do well when subjected to freezing and thawing conditions. They are 15 to 20% costlier than asphalt roads but are being strongly advocated these days due to other advantages. In addition to giving due consideration to various advantages of each type of paving, selection depends on additional factors such as local availability of materials, availability of funds and climatic conditions. Certain factors change with time. Earlier, there used to be scarcity of cement and India went for asphalt-top roads. These days, asphalt that is generated during the refining process of petroleum—a diminishing product tends to become scarce while cement is available in abundance. The present situation reveals that both type of roads shall be adopted by India in future with a tilt towards concrete roads. Equipment Status: Be it the improvement of soil conditions to provide a strong sub-base before the laying of road, be it the compaction of sub-grade, be it the construction of top paving or be it the requirement of utmost precision in road-camber and longitudinal level, highly effective, fully automatic and sophisticated machinery has been developed and even put to use in cases where the authorities have maintained a stringent control over quality of work. That the number of such cases is small is however a different story. While the vehicular and passenger traffic is bound to rise further in India in an unabated manner, there is an immediate need to adopt the latest techniques for road construction and to maintain and widen the existing roads. Forgetting whatever has been done in the past and taking cue from ‘it is never too late’, it is time now to look into the following developments and adopt them to maximum possible extent. Machinery for compaction : Heavy weight has no more remained the necessity for the compaction of the soil. Vibratory rollers have seen a great improvement during the last few years. They can be used for compaction of soil as well as asphalt surfaces. They act on the principle of eccentricity. Their main components are an eccentric weight and a rolling drum. The eccentric weight is made to rotate by a motor. Its connection to the roller drum produces vibrations in the drum which repeatedly lifts itself and bounces against the base sending impact-waves through it and thus compacting it to a greater depth. Such rollers have proved highly effective in sandy soils. Oscillatory rollers are a further improvement over vibratory rollers. In these rollers, there are two eccentric weights instead of one as in vibratory rollers. These two eccentric weights cancel the vertical vibrations of each other and thus cause horizontal vibrations only. Due to the cancellation of vertical vibrations, the drum does not lift above the ground but causes oscillations in it resulting in better compaction of upper layers of soil. Experiments have proved that such rollers even if 25-30% lighter than vibratory rollers give better and smooth compaction. Their fuel consumption is also lesser. Such rollers are quite useful when an under-laid sewer or a near-by foundation is to be saved. Many Indian companies of Delhi, Bangalore, Patna, Nasik, Faridabad and Ahmedabad are producing such rollers with a variation in width, weight, vibration frequency and the number of drums. A very limited use however has been made so far. Greaves Cotton, Dynapac, Tata, Max Mech, Kamal are to name a few. Machinery for paving : In order to have best road surface, excellent finish and excellent riding quality, use of Slip form Pavers has become mandatory in developed countries. Though India has begun using pavers, not very high use of them has been made so far. Pavers are wonderful machines that can give utmost accuracy in road construction. They can be used both for concrete as well as bituminous roads. They are both crawler type and wheel mounted, the former used for larger road width. Pavers can handle up to 300 cubic-meter of concrete per hour even if the thickness of pavement is as little as 30 cm. Earlier the pavers used to be run on rails but now they have given way to slip-form pavers which are capable of bringing a revolution on road construction front. The pavers being produced in India can lay road width varying from 2 metre to 17 metre in a single pass. Indian slip-form pavers are highly versatile and many optional equipments can be attached to them. While the MES, IRCON and a few other departments have built some roads with pavers, a more frequent use needs to be made wherever possible. Ancon International concrete slipform paving equipment put to use in India has shown satisfactory results. Multiquip super screed fixed form pavers used in Madhya Pradesh and Bangalore have shown fast speed in working. Dynapac also offers pavers both in wheel and track versions. Systems for accuracy : Automatic controllers have been developed to control longitudinal level and transversal slope of roads. Electronic level sensors are mounted on the pavers for longitudinal level checking and these continue to check the material thickness with respect to a fixed datum. Transversal slope controllers are mounted on the cross beams and send signals as and when there is a change in slope. In addition to these electronic controllers, manual controls are kept stand-by. Now-a-days, microwave technology and laser systems are being inducted in road-construction-equipment-control. Recycling equipment : Recycling of road material is an aspect extremely important to a country like India who can not spend heavily on relaying altogether new roads along the worn out ones. Patch-work is of no use in India. After one shower or two, roads regain their deteriorated condition. Laying of a seal coat over the worn out road again proves useless as it is unable to provide strength and stability to the road. Moreover relaying of seal coats not only proves expensive but raises the level of the roads thus disturbing the drainage system, side-walks and the berm-position. Cold recyclers have now been developed which mill the broken road surface, add cement or bitumen emulsion to it and relay the course in a single cycle. A lot of saving is thus achieved and road level is also maintained. Mumbai Municipal Corporation have used the Cold recyclers to repair their asphalt roads and results were quite satisfactory. India must respond fully to recycling of road materials instead of resorting to patch-work as most of its roads are asphalt-topped. (CW has already covered this equipment in detail in November,2006 issue). Future Developments: In addition to above developments, a lot of experimentation is under progress. Use of Fibre-reinforced concrete, pre-stressed concrete, roller compacted concrete and vacuum processed concrete is being tried a lot. Even the pavement design methods are undergoing a significant change as the engineers want to get rid of age old empirical formulae. Need of the hour is to reframe our road specifications, induct compulsory use of machinery in road construction, recycle the used material by milling the existing roads so as to bring savings and to free the country of all the criticism that the pathetic condition of its roads invites. Road Marking Equipment: Traffic markings such as Centre lines, Zebra Crossings, Edge bars, Stop bars, Direction arrows, Bicycle lane markings and Parking lines on the roads play an important role in the regulation of traffic. Often, these get rubbed off and need frequent re-painting. This problem has assumed more significance with the increase of traffic and advent of radial tyres which have a larger contact area with the road surfaces. Some permanent solution needs to be found for this recurring problem of traffic markings getting rubbed off again & again. Another important factor is to ensure visibility of road markings during night time. In general, this aspect is not paid due attention. Mostly, adequate light is available at the crossings but not along the routes. It is not possible to provide fluorescent paint markings all along the road lengths because of cost restraints and high glare problems. Fluorescent paint glare may sometimes blind the vehicle drivers resulting in their losing the balance and causing mishaps. To overcome the problem, a new product has been invented and now, it is available in India also. It is a cold plastic coating material that gets hardened through a chemical reaction and serves as a permanent marking paint. This cold setting marking paint is thixotropic and carries refractive glass beads in it which shine during night without causing any glare to the drivers and make the markings visible during night. The paint hardens with in 20 to 30 minutes of its application and thus can be used without much hindrance to road traffic. Produced in both the colours used for roads i.e. white and yellow, it has two components which are mixed and stirred well before applying. As the setting time of the mixed paint is 20 minutes, the mixture need to be used within this period. Thus machine marking is preferred over manual marking for better efficiency, good and accurate marks and optimum coverage. Coverage capacity is quite good, consumption ranging between 1.5 to 2.0 kg per sq.metre per mm thickness. The paint is weather resistant, skid resistant and tested for day and night visibility. White paint has the properties of non-yellowing and oil spill resistance also. The Road marking machine produced to apply this paint carries an Auto Glass Bead Application system. If the machine capacity is 75 kg, the glass bead container has a corresponding capacity of 10 kg. However the flow of glass beads can be increased or decreased through a knob provided for the purpose. Glass beads application activates automatically as soon as paint application begins. The bead container has a level indicator which ensures addition of more quantity of beads to the container well in time. The machine is quite cheap and proves economical than manual painting. Aquarius Technologies is producing versatile road marking machines in India.
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Tip of the Moment
53 grade cement is strongest among all these though its cost difference is marginal.
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IMP : Due to His Pre-Occupations, The Author Is Unable To Find Time To Compile The Tips In Book Format. As And When, The Book Is Completed And Near Publication, It Will Be Notified On The Website. The Author Expresses His Gratitude To The Readers And Site-Visitors For The Huge Demand Made By Them For The Book.
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