icsci keynote 10 dr. s gangopadhyay

8/10/2019 Icsci Keynote 10 Dr. s Gangopadhyay

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INNOVATIVE TECHNOLOGIES FOR SUSTAINABLE MAINTENANCE OFFLEXIBLE PAVEMENTS

Dr. S. Gangopadhyay 1 and K. Sitaramanjaneyulu 2 1Director, CSIR - Central Road Research Institute, New Delhi

2Senior Principal Scientist, CSIR - Central Road Research Institute, New Delhi

1.0 INTRODUCTION

Indian road network of 3.3 million km of total road length has second largest roadnetwork next to USA. We are still adding thousands of kilometers of road length

through the large number of infrastructure programmes that are currently going on. Tomeet the need of growing economy, the pace of infrastructure development will haveto be enhanced. The road being an important infrastructure full attention is being given

by Government to create better quality roads which can take large volume of trafficand ensure fast and safe travel. Special programmes under NHDP to develop NationalHighways, JNNURM for developing urban infrastructure, PMGSY for betterconnectivity to rural areas are some examples. All these programmes are beingimplemented with Central and State Government funds and PPP mode. It is expectedthat an investment of Rs. 8 to 10 lakh crores will be made in road sector alone in thenext 12 to 15 years.

The ambitious road modernization and development projects provide immenseopportunities to introduce innovative technologies in maintenance of flexible

pavements that would lead to high quality roads and reduce life cycle costs. Severalinnovative technologies have come up in the last one decade in maintenance industry.This paper deals with a brief of these technologies which have been suitability adopted/ demonstrated in India for sustainable maintenance of flexible pavements.

2.0 INNOVATIVE TECHNOLOGIES FOR SUSTAINABLE MAINTENANCEOF ROADS

The tendency to use only conventional materials and mixes in road maintenance programmes are the biggest barrier to innovation. Today very limited options areavailable to deal with a variety of demanding situations in a cost effective manner. Useof innovative technologies appropriate to specific conditions will have to beencouraged for assured performance and durability. Capabilities will have to be

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improved for evaluating alternatives so that new specifications and new technology products can be used in practice with confidence. This is high time to promote use ofnew products, specifications and technologies that satisfy the requirements of

performance, durability and cost savings. A brief of innovative technologies have been presented in this paper which can be suitably adopted for sustainable maintenance of pavements.

2.1 Microsurfacing

Microsurfacing is most versatile tool in road maintenance and is a major breakthroughamong environmental friendly cold mix technologies across the world. Thistechnology have advantage over conventional slurry sealing, being slightly thicker inapplication, fast and least effected by temperature stresses. Microsurfacing can be

successfully used in different situations for sustainable maintenance of roads.

Microsurfaing is a mixture of polymer or latex modified bitumen emulsion, well gradedcrushed fine material aggregate, mineral filler (portland cement), water and chemicaladditives ( identical to emulsifier). It is generally applied using a microsurfacing paver(Photo-1) without rolling at ambient temperature. This is generally laid in 6 to 12 mmthickness. Cement is used as accelerator to control cohesion and breaking time ofemulsion in a microsurfacing mix. Special additives are used to increase the time ofinitial breaking of emulsion in microsurfacing mix depending upon prevailing climaticconditions. Microsurfacing is generally opened to vehicular traffic within an hour at a

controlled speed sometimes in 2 to 3 hours in adverse climate conditions. Cold weatherwith high humidity do require longer time for opening to traffic or in such situations,dose of additives may be reduced or cement may be enhanced.

Photo-1: Typical View of Laying of Microsurfacing with Paver

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The advantages of microsurfacing over hot mix surface treatments are as under: preserve the pavement structural strength and prevent ingress of water seal fine and medium cracks, restore nonskid characteristics of surface. rejuvenate dry and hungry surface and prevent ravelling. increase visibility of pavement surface at night. reduce entry of air and water into existing lower layer of pavement. checks requirement of corrective maintenance and reconstruction. raise in pavement height is marginal say 6 to 12 mm as compared to 25 to 40 mm

in case of conventional thin hot mix overlay. non polluting, consumes only 10 to 15% energy of the quantum consumed in 20 to

40 mm thick hot mix laying.

The limitations of microsurfacing as maintenance treatments are as under: microsurfacing treatments may not be successful for structurally unsound

pavements with characteristics deflection greater than 1 mm. microsurfacing treatments may not be successful for surface with extensive deep

and wide cracks ( > 6mm). being a thin layer 6 to 12 mm, the unevenness may be corrected marginally. cannot be laid by manual methods, microsurfacing paver is essential.

The first test section of microsurfacing was laid in the year of 2001 on Prithaviraj Roadunder supervision of CRRI and evaluated for five years, thereafter more than 50 roadshave been resurfaced with microsurfacing in Delhi under jurisdiction of PWD &

NDMC.

The tentative specifications for slurry seal and microsurfacing are given in IRC: SP:81-2008. Photo 2 shows roads laid with microsurfacing treatments on Delhi Roads.

Photo - 2: Roads Laid with Microsurfacing Treatments on Delhi Roads

Kamal Arraurk MarRa a i Mar

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2.2 Stone Matrix Asphalt (SMA)

Stone Matrix Asphalt was developed in Germany. These mixes may be prepared bymodification of conventional bituminous binder with polymeric materials or bymodifications in matrix of mix. The Stone Matrix Asphalt mix is a gap graded hot mixwhich contains 70 to 80 percent coarse aggregate, 6 to 7 percent of binder, 8 to 12

percent of filler and about 0.3 to 0.5 percent cellulose fiber or other modifier. Thehigher amount of coarse aggregate in SMA as compared to dense graded mixturehaving more contact points (Photo-3) which provides better stone to stone contact

between the coarse aggregate particles, such contact points provide a high resistance torutting and influence to reduce the type and amount of binder on rutting, while thehigher binder content in mortar adds to durability of mix. The stabilizing additives actsto hold the bitumen binder in the mixture at the high temperature during productionand placement of mix and eventually reduces the drain down of the binder.

BC SMAPhoto-3: Comparison of Stone to Stone Contact Points of BC and SMA

SMA exhibits superior properties in several key areas when compared withconventional asphaltic concrete, these being:

resistance to rutting due to slow, heavy and high traffic volume. resistance to deformation at high pavement temperatures. improved skid resistance. noise reduction over conventional alternative pavement surfaces. improved resistance to fatigue effects and cracking at low temperatures. increased durability. reduced permeability and sensitivity to moisture .

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The reasons for these above positive behavior of SMA pavement surface with heavilytrafficked conditions can be attributed to its design principles. Number of test sectionson NDMC and MCD roads and roundabouts in Delhi have already been laid with SMA.The tentative specifications for Stone Matrix Asphalt are given in IRC: SP: 79-2008.Photo -4 shows the typical view of laying of SMA mix. The typical view of surfacetexture of freshly laid SMA is shown in Photo- 5 .

Photo- 4: Typical View of SMA Laying Photo- 5:Surface Texture of Freshly Laid SMA

2.3 Warm Mix Asphalt (WMA)

Warm Mix Asphalt is not a hot mix asphalt, it is just warm mix. The warm mix asphalt production temperature typically ranges from 100 to 140 C 0, whereas for Hot MixAsphalt (HMA) it ranges between 150 to 170 C 0. The WMA technology allows a

reduction in the temperature at which asphalt mixes are produced and placed. Thesetechnologies tend to reduce the viscosity of the asphalt and provide complete aggregatecoating at lower temperatures. Photo- 6 shows typical view of Warm Mix Asphaltlaying.

Photo- 6: Typical View of Warm Mix Laying

The WMA has certain distinct advantages over Hot Mix Asphalt. The range of potential benefits from WMA technologies includes:

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as the temperature level is relatively low, air-pollution caused due to emission and

fumes is less. Also, the ageing of asphalt binder during the heating process iscontrolled considerably.

less energy requirements for production of mix. temperature drop during mix transportation is no longer a concern. The

construction season expands and the haul distance increases. compacting efforts is less so as to achieve a specified compaction level.

The production of WMA mix is simple and does not require any major modificationsto the hot mix plant system. Various ingredients used in the WMA production are

patented products. Two major types of WMA technologies are those that use water andthose that use some form of organic additives or wax to affect the temperaturereduction.

Warm asphalt technology seems to be quite promising. It consumes 30% less energy,reduces carbon dioxide emission by 30% and reduces dust emission by 50- 60%compared to hot mix asphalt. Further research is needed so as to validate the expectedfield performance of such a mix,specially with reference to mix compatibility, rate ofgain of structural strength after construction, rutting potential, moisture sensitivity.Two years back, CRRI has laid a test section with Evotherm TM at Delhi State Industrial& Infrastructure Development Corporation (DSIDC) site at Bawana Industrial Area inDelhi. It is the first test section with WMA in India and being monitored periodicallyfor its performance.

2.4 Plastic Waste Utilization in Road Maintenance

The plastic waste could be used in road maintenence after proper processing as anadditive would enhance the life of the roads and also solve environmental problems.Plastic is everywhere in todays lifestyle. It is used for packaging, protecting, servingand even disposing of all kinds of consumer goods. With the industrial revolution,mass production of goods started and plastic seemed to be a cheaper and effective raw

material. Today, every vital sector of economy starting from agriculture to packaging,automobile, building construction, communication on Infotech has been virtuallyrevolutionized by the applications of plastics. Use of this non-biodegradable productis growing rapidly and the problem is what to do with plastic waste. The use of plasticwaste has been a concern for scientists and engineers for a quite long time. Thescientists / engineers have developed a way to use plastic waste for road construction.The following types of plastic waste can be used in the construction of roads:

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films (carry bags, cups) thickness upto 60 micron hard foams, any thickness soft foams, any thickness laminated plastics thickness upto 60 micron (aluminum coated also) packing

materials used for biscuits, chocolates etc.

Polyvinyl Chloride (PVC) sheets or flux sheets should not be used in any case. When processed plastic waste mixed with hot bitumen, plastic melts to form an oily coat overthe aggregate and the mixture is laid on the road surface like a normal bituminous road.The various steps involved for production of bituminous mixes using plastic waste areas under:

plastic waste (bags, cups, thermocole) cut into a size between 2.36 mm and 4.75mm using shredding machine. The PVC waste should be eliminated.

the aggregate is heated upto 165 0C and transferred to mixing chamber. similarly, the binder is to be heated upto a maximum of 160 0C to have good binding

and to prevent weak bonding (monitoring of the temperature is very important) at the mixing chamber, the shredded plastic waste is to be added. It get coated

uniformly over the aggregate within 30 to 60 seconds, giving an oily look. the plastic waste coated aggregate is mixed with heated bitumen and the resulted

mix is used for road construction. The road laying temperature should be in between110 0C to 120 0C.

The following are the advantages by using plastic waste in road construction: easy laying process without any new machinery in-situ process use of lesser percentage of binder and thus saving on bitumen resource use of plastic waste for a safe and eco- friendly process both Mini Hot Mix Plant and Central Mixing Plant can be used only aggregate is polymer coated and bitumen is not modified use of VG-10 & VG- 30 bitumen is possible no emission of any toxic gases like dioxin

The durability of the roads laid out with shredded plastic waste is expected to be betterthan the conventional ones. The binding property of plastic makes the road last longer

besides giving added strength to withstand more loads. Rainwater will not seep through because of the plastic in the bitumen. So, this technology will result in lesser roadrepairs. The cost of plastic road construction may be slightly higher (10 to 15%)compared to conventional method. Plastic roads would be a boom for Indias hot andextremely humid climatic zone, where temperature frequently cross 50 0C and terrestial

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rains create havoc, leaving most of the roads with big potholes. A number of roadshave already been laid with waste plastic in Delhi under supervision of CRRI. Photo-7 shows typical view of roads laid with waste plastic in East Delhi area.

Photo-7: Typical View of Roads Laid with Waste Plastic in East Delhi Area

The government is keen on encouraging the setting up of small plants for mixing waste

plastic and bitumen for road construction. It is hoped that in near future we will havestrong, durable and eco-friendly roads which will relieve the earth from all types of

plastic waste.

2.5 Recycled Asphalt Pavement

Recycling of Hot Mix Asphalt (HMA) material results in a reusable mixture ofaggregate and asphalt binder known as Reclaimed Asphalt Pavement (RAP). Recyclingof asphalt pavements is a valuable approach for technical, economical, andenvironmental reasons. Use of RAP has been favored over virgin materials in the lightof the increasing cost of asphalt, the scarcity of quality aggregates, and the pressuringneed to preserve the environment. There is significant savings when RAP is used.Considering material and construction costs, it was estimated that using reclaimedHMA pavement provides a saving ranging from 15 to 35% for a RAP content varying

between 20 to 50%. The use of RAP also decreases the amount of waste produced andhelps to resolve the disposal problems of highway construction materials, especially inlarge metropolitan cities. It is concluded so far that the use of RAP will not only be a

beneficial alternative in the future but will also become a necessity to ensure economiccompetitiveness of flexible pavement construction. The maximum percentage of RAP

that can be used, ranging typically between 10 to 50%. However, high percentage ofRAP are not commonly used in practice. A maximum RAP percentage of 50% may beallowed in HMA shoulders and stabilized sub-bases. However, ensuring confidence inthe design procedure and the success of using RAP would require addressing manydurability concerns related to the interaction between virgin and recycled materials.

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One major factor that is still unclear is the level of interaction between aged and virginasphalt binders. If RAP acts like a black rock, the aged and virgin binders will notinteract. Hence, it would be assumed that RAP does not significantly change the virgin

binder properties. However, it is usually assumed that RAP does not act as, a blockrock and that the aged asphalt blends with the virgin binder during mixing. In fact,many design procedures assumes that all the aged binder is fully available in themixture and would effectively contribute to the blend. This means that the amount ofvirgin asphalt binder can be reduced by the full amount of asphalt binder in the RAPfor the percentage specified. Relative to asphalt pavement recycling, there are severalmethods available. Therefore, each road being considered for recycling must becarefully evaluated to determine the method most appropriate. The factors shouldinclude:

o existing pavement condition,o existing pavement material types and thickness,o

recycled pavement structural requirements ando availability of recycling additives.

HMA recycling can be divided into two basic categories based on the recyclingmethods used :

Hot Recycling Cold Recycling

2.5.1 Hot Recycling

Hot recycling is so named because RAP is used as an aggregate in HMA. In hotrecycling, old HMA pavement is removed, broken down into aggregate-sized chunksand then incorporated into new HMA as an aggregate. There are two basic methods foraccomplishing this:

Recycled Hot Mix (RHM): Recycled Hot Mix (RHM) is the most common wayof using RAP. Basically, new HMA is produced at a batch or drum mix plant towhich a predetermined percentage of RAP is added (Photo-8) .

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Introduction of RAP material into Drum Mix PlanRemixing and Laying

Photo-8: Hot Mix Recycling

RAP addition may require longer HMA plant heating times. This can sometimes reduce plant output by as such as half. In general, RAP will be more viscous than new HMA

because of asphalt binder ageing. Therefore, if enough RAP is added, a softer asphalt binder should be used. After milling or crushing, RAP gradation is generally finer than pure virgin aggregate because of the degradation that occurs during removal and processing.

Hot In-Place Recycling (HIPR): Hot in- place recycling (HIPR) is a less commonform of hot asphalt recycling (Photo-9) .

Pavement surface before recycling Laying is in progressPhoto-9: Hot In-Place Recycling

There are three basic HIPR construction processes in use, all of which involve a

specialized plant in a continuous train operation:

(a) Heater scarification: This method uses a plant that heats the pavement surface(typically using propane radiant heaters), scarifies the pavement surface using a

bank of non-rotating teeth, adds a rejuvenating agent to improve the recycledasphalt binder viscosity, then mixes and levels the recycled mix using a standardauger system. The recycled asphalt pavement is then compacted using

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conventional compaction equipment. Heater scarification is limited in its abilityto repair severely rutted pavements, which are more easily rehabilitated with aconventional HMA overlay.

(b) Repaving: This method removes (by heating and scarification and / or grinding)the top 25 to 50 mm of the existing HMA pavement, adds a rejuvenating agent toimprove the recycled asphalt binder viscosity, places the recycled material as aleveling course using a primary screed, and simultaneously places a thin ( usuallyless than 25 mm) HMA overlay. Conventional equipment and procedures are usedimmediately behind the train to compact both layers of material.

(c) Remixing: This method is used when additional aggregate is required to improvethe strength or stability. Remixing is similar to repaving but adds new virginaggregate or new HMA to the recycled material before it is levelled.

HIPR is only applicable to specific situations. First, air void content of the existing

asphalt binder must be high enough to accept the necessary amount of asphalt binderrejuvenator. Second, HIPR can only adequately address shallow surface distress problems (less than 50mm). Third pavements with delaminations (subsequent layersnot binding together) in the top 50 mm should not be considered for HIPR projects.Finally, pavements that have been rutted, heavily patched, or chip-sealed are not goodcandidates for HIPR projects.

2.5.2 Cold Recycling

Cold recycling is so named because RAP is used as an aggregate in cold mix asphalt.In cold recycling, old HMA pavement is removed broken down into aggregate-sizedchucks and then combined with an emulsified or foamed asphalt. This mix is thentypically used as a stabilized base course for reconstructed pavements. There are two

basic cold recycling methods:

Cold In-Place Recycling (CIR): Cold in-place recycling (CIR) is the processingand treatment with bituminous and / or chemical additives of existing HMA

pavements without heating to produce a restored pavement layer. It involves thesame process of cold plant mix recycling except that it is done in-place by a trainof equipment (Photo-10) . CIR is best suited for cracked pavement with structurallysound, well drained bases and subgrades.

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Photo-10: Cold In-Place Recycling

Cold Plant Mix Recycling: Cold plant mix recycling, the less common of the twocold recycling methods, involves mixing RAP with as asphalt emulsion or foamedasphalt at a central or mobile plant facility. A rejuvenating agent can be added toimprove the recycled asphalt binder viscosity and new aggregate can also be addedto improve overall performance. The resulting cold mix is then typically used as astabilized base course.

CRRI has worked as an independent agency to check the quality of hot in-placerecycling work on M.B. Road, New Delhi. However, the other Recyclingtechnologies, as discussed above yet to be implemented / demonstrated in India.

3.0 CONCLUDING REMARKS

In view of the growing number of the vehicles with the ever increasing axle loads andincreased tire pressures, the conventional paving technologies do not perform itsintended function for the anticipated design life. Therefore, various technologiesdescribe above have been adopted and validated to have extended performance. Thesetechnologies have good prospect and chance to flourish in India looking at the quantumof the infrastructure activities going on. However, one has to be careful in theapplication of these technologies as they all require very stringent quality control,excellent workmanship and expertise. The following areas which require furtherresearch in this direction are as under:

Development of technologies to save aggregates

Innovative technologies for utilization of waste and marginal material Design methods and mixes towards reduced pavement thickness Warm and cold mix technologies for construction/maintenance Maximum use of RAP in construction and maintenance Evaluation of non conventional material using Accelerated Pavement Testing

Facility (APTF) Prevention of failure of pavements due to stripping and rutting

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icsci keynote 10 dr. s gangopadhyay

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