Featuring few measures that help buying slipform pavers.
Slipform concrete paving has been extensively used by the worldwide paving industry since its development in 1940s. In India also slipform concrete paving has been carried out for nearly more than 15 years. It is entirely different from the fixed-form paving, slipform paving brings together concrete placing, casting, consolidation, and finishing into one unique process. In this paving process, concrete mixture with a slump of around 30 is placed in front of a paver. As the paver moves forward, the mixture is spread, levelled, consolidated (by equally spaced internal vibrators), and then extruded. After extrusion, the fresh concrete slab can hold shape for further surface finishing, texturing, and curing until the concrete sets. Because of the low consistency of the mixture, a great deal of vibration is needed to move entrapped air and consolidate the concrete. Take a look at what experts suggest while going for slipform pavers:
Scope of a project
P. Arunagiri, Director – Business Development, Allen Buildwell Pvt Ltd says, “One has to first understand the project needs. We can get away with a fixed-form paver when we are working on interior or village roads. When the subject of matter comes to NHAI or NH roads or even to an extend PWD jobs now a day’s specify clearly paving by slipform pavers. The reason to mention is we get good quality roads at a faster time compared to other paving methods adopted in the industry.”
Procurement plan to ensure timely delivery of machine
Current governments focus on rigid pavement (concrete roads) for construction of national highways has created a sudden surge in demand on slipform pavers. “The lead time for delivery of slipform pavers is quite high extending up to 5 to 6 months with current existing players in India. As this machine is not manufactured in India and mostly imported from Germany and the USA with limited good options a proper procurement plan is important to ensure timely delivery of machine,” says Ratan Lal Kashyap, Sr. Vice President – Procurement, G R Infraprojects Ltd.
He adds, “Today projects being time bound and tight on rates contractors strive to complete the project on or before time and earn profit. For this the uptime of the machine is very crucial where the machine performance and consistency is important, after market service support and spare parts availability becomes as one important considerations in decision making. Being as costly machine no standby machines are available so any breakdown of machine can lead to huge time loss leading to idling of entire manpower, machine fleets related to this activity. Machines precision and consistent paving saves on concrete wastage and avoids and pavement repair at later stage of the project. Expert engineers availability with vendors at times becomes a challenge as calling expert engineers from overseas are time taking.”
With current demand of concrete roads in India slipform paver’s manufacturers need to gear up and support contractors by all means to help them move as per the project requirement, belives Kashyap.
Selection of proper specification
“Selection of proper specification considering the project requirement like width of the road, paving speed, volume of paving, finish , compaction, dowel bar inserter, side ties bar inserter, texturing machine etc. are few of the major considerations while finalising the machine,” states Kashyap.
He adds, “Freezing the correct specification is very crucial with team of civil engineering, design and mechanical as any miss on this will lead to improper paving or rejections by client. There are few options available like having small capacity crane on slipform paver brings lots of ease on handling dowel bars and handling repairs.”
Quality of concrete, proper curing methods and preparation of subbase
Arunagiri feels that whatever the best available machine is used the end result of a concrete road depends on the quality of concrete, proper curing methods preparation of subbase. The native soil on which the pavement is built must be graded and compacted. Preparation of the subgrade is often followed by the placing of a sub base a layer of material that lies immediately below the concrete. He further opines, “The essential function of the subbase is to prevent the displacement of soil from underneath the pavement. Subbases may be constructed of granular materials, cement-treated materials, lean concrete, or open-graded, highly-permeable materials, stabilised or un-stabilised. Once the subbase has hardened sufficiently to resist marring or distortion by construction traffic, dowels, tie bars, or reinforcing steel are placed and properly aligned in preparation for paving.”
Categories of slipform pavers
Talking about the classification of slipform pavers Arunagiri says, “The slipform pavers are categorised as 2 track and 4 track pavers, normally a 2 track pavers does not come with an automatic dowel bar inserter whereas 4 track paver has this attachment in built. Now based on the scope of the project and movement of vehicles one can decide the distance of the dowel bars and based on that we can decide to go paver with automatic DBI or without. The most prominent model of 2 track paver available in the world-wide market is SF-1700 by Power Pavers Inc. USA. When we have smaller projects from PWD or any state under taken projects other than NHAI we can go for a 2 track paver as it is
half the cost when compared to a 4 track paver. For narrow roads and where there is no sufficient place for movement of tracks its recommended to go for a 2 track paver as the width of the track is smaller and it can be easily transported when compared to a 4 track paver.”
Huge capital investments
Explaining the criteria of buying slipform pavers Pankaj Udeshi, Asst. General Manager Procurement, Supreme Infrastructure India Ltd says, “Huge capital investments are required to procure this machine, we will go for procurement only if we have right projects in line in which this machine will be perfectly suitable for used for next 5 years and we have proper plan to get new suitable projects in coming future.”
Udeshi outlines the factors to buy slipform pavers as follows:-
• Huge and faster production capacity: This machine provides us high production rates with time saving and quality and enables us to complete the job in time.
• Digitalisation: Technology is the biggest contributor to the creation of the smart paver. Due to high digitalised and its intelligent control systems it reduces requirements of manpower to handle the job and saving huge amount.
• Brand of machine: For procurement of slipform paver machine brand name is important for us.
Width of road and density of traffic
Wirtgen group provides concrete slipform pavers and these are available in working widths of 2.5 to 16 metre.
Ramesh Palagiri, Managing Director & CEO, Wirtgen India says, “The width of the road and the density of traffic in terms millions of axle loads to be paved is one of the prime criteria in selecting a slipform paver. For an existing state highway which is to be developed from single lane to two lane with shoulders, where the existing road cannot be disturbed due to ongoing traffic, the paving has to be done in 2 passes and you may have to select a paver with width of around 5 metre, whereas for a new Greenfield project the paving can be done in a single pass where the no. of lanes to be paved would determine the width of the paver required. Another important criterion for selection is whether the Dowel bars are to be inserted manually or automatically, though it is always recommended to use automatic dowel bar inserter to ensure the right quality. The type of the project and the timeline for execution also determines the type of machines to be procured.”
Wirtgen Group has been involved with the road development in India since the golden quadrilateral days starting with the Mumbai Pune expressway. “Wirtgen slipform pavers have several innovations like the automatic Dowel Bar Insertor system (DBI), super smoother, central tie bar inserter, oscillating beam etc,” says Palagiri.
Udeshi believes that slip form pavers manufactured by many well-known companies, comes in the width range of 1 to 16 meters. He further opines, “The heavy duty, torsion-re-sistant machine main frame makes a significant contribution to producing the required evenness of the concrete surface; in simple word it provides high quality of concrete surface. It has facility of continuously keep moving while inserting the dowel bars or tie bars and this is also possible in evenness of concrete slab, this will help us to prevent uncontrolled cracking of the concrete while we inserted dowel bars and thus will help significantly contribute to achieve intending design life concrete pavement.”
Major assignment in the agenda of government
Development of roads in the entire country are the major assignment in the agenda of government. The Road Transport and Highways Ministry is considering an option to make use of concrete cement mandatory as a part of the bid for fully government-funded projects as well as public-private partnership projects. The Ministry discussed the issue at some recent meetings.
Union Minister of Road Transport and Highways, Nitin Gadkari had stated his preference for concrete cement roads as opposed to bitumen. Cement, now the preferred choice of Road Ministry.
The Ministry is also considering entering into rate contracts with companies to buy concrete and cement so that contractors can acquire the same at cheaper rates. This also involves commitment on volumes.
“Procurement of large volumes for national highway projects raises the possibility of discounts. The developers can buy cement at a lower price after getting an authorisation letter from the Roads Ministry or NHAI,” concludes Udeshi.