runway resurfacing and repairing using modern materials and techniques

Runway Resurfacing and Repairing Using Modern Materials and Techniques Seminar Report 2012-2013

1.INTRODUCTION

The transport modes like roadway, waterway and airway have

been used by the mankind using land, water and air. In the past railways were

assigned priority of developments, Because it was one mode of transport,

which helped mass transportation of goods and passengers. Railways and

roadways in India and abroad are in competition today for providing better

transportation facilities. Air transportation is the most suitable transportation

technique for long distance travels. So runway has very importance. Runway

is a long and comparatively narrow strip, which is paved for small

aerodromes.

Repair and resurfacing of runway is a complex activity, which

requires comprehensive engineering evaluation, selection of suitable materials

commensurate to problems and proper co-ordination of construction procedure

and activities .It also demands setting up adequate quality planes and quality

assurance methods. For runway resurfacing it is required to determine the

nature and extend of deterioration and also the causes of deterioration. For this

it is essential to carry out detailed study including overall projection

evaluation so as to evolve suitable repair alternatives.

Dept. Of Civil Engg. 1 GPTC Muttom


2. The Pavement Classification Number- Runway Strength Rating and Load Control System.

The Air craft Classification Number/ Pavement Classification Number

(CAN/PCN) system has been adopted by ICAO as the standard for the

international reporting of air field pavement bearing strengths .The ACN-

PCN system of rating air port pavements is designated by the international

civil aviation organization (ICAO) as the only approved method for reporting

strength. The ACN- PCN method came in to use in1981.

The ACN- PCN system is simple to use. Each air craft is assigned a

number that expresses the structural effect on a pavement for a specified

pavement type and a sub grade category. Each air port operating authority

reports site pavement strengths using the same numbering system. The

pavement is capable of accommodating unrestricted operations provide the air

craft load number is less than or equal to the pavement strength number.

Maximum tire pressure limitations may also be applied to some pavements

which may further restrict certain air craft operations. The ACN is based on

static application on aircraft loads to the pavement surface making them

somewhat conservative in nature



The ACN and PCN are defined as follows:

• ACN is a number that expresses the relative structural effect of an

aircraft on different pavement types for specified sub grade strengths

in terms of a standard single wheel load

• PCN is a number that expresses the relative load carrying capacity of

a pavement in terms of a standard single wheel load

• The system is structured so that a pavement with a particular PCN

value can support, without weight restrictions ,an aircraft that has an

ACN value equal to or less than the pavements PCN value



3. ASPHALT APPLICATIONS

3.1 Airfield uses of asphalt

Most of the world’s paved roads are surfaced with asphalt, Asphalt is

obtained by fractional distillation of petroleum crude, which gives good

performance and durability under the most heavily trafficked conditions.

Asphalt is obtained by fractional distillation of petroleum crude. These

materials are also widely used in the construction of hard standing and parking

areas for both light and heavy vehicles. They are therefore eminently suitable

for use in the construction and surfacing of access roads, perimeter roads and

vehicle parking areas on airfields.

Without hard paving, access may be difficult to the airfield, flying may

be restricted in inclement weather or the facilities may not come up to the

minimum standards required by the regulatory authorities for passenger

carrying aircraft. The following areas on a typical airfield are likely to

require hard paving:-

• runways

• taxi-ways providing access to runways

• aircraft parking, re-fuelling or servicing aprons

• hanger floors



• car, bus or commercial vehicle parking areas

• access roads

• edge drainage (French Drains) for runways and taxiways

In each of these areas different considerations apply. For example,

runways require good skid resistance and surface water drainage for good

braking, an even surface regularity to ensure passenger comfort and minimum

risk of damage to delicate electronic components and adequate strength to

support the high wheel-loadings of modern aircraft. Where jet-engined aircraft

operate, freedom from loose particles is an additional, essential requirement to

avoid the expensive damage that can be caused to jet-engines from ingestion

of foreign objects (known as Foreign Object Damage or FOD). This term may

also be used for “Foreign Object Debris” when referring to any detritus or

loose particles on or near to runways or taxiways.

For aircraft parking areas the main requirement is adequate stability

under high wheel-loadings; for paved areas where aircraft will undergo re-

fuelling and servicing, the principal considerations are adequate stability under

wheel-loads and heavy point loads from maintenance machinery as well as

good resistance to oil spillage

Runways need to be constructed with sufficient strength to carry the

moving aircraft. Runways require a higher degree of resistance to skidding

and aquaplaning in view of the higher speeds involved. One means of



achieving the latter, now employed on many major runways in the UK, is to

use an open-graded Porous Asphalt surface course traditionally known as

Porous Friction Course as the running surfacing. This acts as a drainage layer

to prevent surface water adversely affecting aircraft tire grip on the surfacing

in wet weather.

Beneath the Porous Friction Course a strong impervious binder course

of Hot Rolled Asphalt or a dense Asphalt Concrete known as Marshall

Asphalt is required laid to adequate falls. Alternatively the new surface course

may be laid directly on an impervious existing surfacing.

When resurfacing work is being undertaken on runways, it is essential

that the existing surfacing is of good regularity and laid to adequate falls or the

levels are corrected by applying an appropriate regulating layer. This is of

particular importance if a Porous Friction Course is to be applied and ensures

that water is not held in the new surfacing to lead to heavy ice formation in

winter.

Where relatively light aircraft are involved standard road surfacing

materials, namely Hot Rolled Asphalt, close-graded/dense Asphalt Concrete

or Stone Mastic Asphalt specified using the guidance from PD 66911 and the

appropriate European Asphalt Standard will provide good durability and

adequate performance. If Hot Rolled Asphalt is employed, a 35% stone



content mix without the application of pre-coated chippings should give good

performance and durability

3.2 MODERN ASPHALTS

Most runway resurfacing is carried out at night, with contractors

given access for just a few hours. They do the work in short bursts, completing

a section each night and reopening it the next day. It is not surprising, given

these constraints, that designers and contractors tend to stick with tried and

tested mixes for the new runway surface – usually Marshall Asphalt, a

continuous graded aggregate mix that gives a harder surface than traditional

hot rolled mixes.

Nynas has, over the years, developed a number of products that can be

used in runway surfacing and other heavily trafficked areas within airports.

These include binders with high resistance to damage by fuel oils and de-icing

fluids – a major issue for airport managers – as well as binders for thin

surfacing and foam mixes.

One fuel damage resisting product Nyguard , was used at Bristol

Airport to bring two redundant runways back into use as taxiways and for

aircraft refueling and parking(fig.1). These ancillary areas are seen as lower

risk.



Fig.1 Nyguard, was used at Bristol airport to bring two redundant runways back in to use

Nynas has developed the product further to produce Nyguard

HR(fig.2), a hot mix binder specifically designed for heavy duty areas like

airfields, docks and bus bays. As well as its fuel damage resisting properties,

the binder gives cohesion values up to five times greater than equivalent

paving grade bitumen, making it much more resistant to shearing forces and

resulting scuffing, tearing and deformation.



Fig.2 Nyguard HR, a hot mix binder specifically design for heavy duty areas

One issue that may make airport owners more willing to look at

non-traditional mixes for runways is sustainability. With local authorities

setting targets for recycling, and commercial firms increasingly aware of

waste and energy consumption, there is increasing pressure to reuse material

in runway resurfacing.

In a recent contract at Liverpool Airport, Tarmac reused runway

planings for sections of recycled pavement. These areas – the outer strips of

the runway – were re-constructed using Nyfoam, a binder specifically

developed by Nynas for foam mixes and used last year on the UK’s largest

road recycling contract on the A38 in Devon.

4



The successful application of the technique at Liverpool is likely

to lead to other airports considering recycling for future resurfacing projects.

While Nynas’ specialist products have so far mainly been used

on ancillary areas, such as taxiways and parking bays, the company also has

experience of supplying specialist materials for main runways. At Exeter

Airport, for example, its Nypol TS polymer modified binder was used by

Bardon in the construction of a “Super AirMat” runway – a thin surfacing

alternative to traditional Marshall Asphalt.

Super AirMat contains a 10mm nominally sized grit-stone with a

very high polished stone value to give the surfacing a high level of grip. The

Nypol TS is designed to give good adhesion and cohesion with the stone, and

extra durability comes from adding cellulose fibres to the asphalt mix.

The Super AirMat mix was designed specifically for airfields,

and is laid in a single pass, making it a very efficient way to surface large

areas in a relatively short time.



4. Rubber Removal Techniques

The most common methods of pavement retexturing are:

• High Water Pressure,

• Ultra High Water Pressure (Track Jet),

• Chemical,

• Shot Blasting,

• Mechanical Process.

4.1 High Pressure Water blasting (HPW)

Rubber is removed by means of rotary devices that move along

the surface as it cleans. This is done utilizing up to 30 gallons of water per

minute at pressures of between 100 to 1,000 bar . The water that penetrates the

surface effectively cleaning rubber deposits creates an hydraulic effect. This

helps to increase the frictional values and surface texture of the pavement. A

combined suction part or a sweeper that picks up the rubber debris during its

operations usually accompanies it. This allows for the pavement to be easily

and quickly returned to operations and is especially advantageous in airport

operations where time constraints and short possession time is common.

Benefits of using this technique are:

• The speed at which rubber is removed (1,200 m² per hour are claimed).



• The cost efficiency of the process (water is generally provided).

• The improved friction characteristics of the pavement due to penetration

of the water and the removal of rubber.

• The ease of getting off the runway in the event of an emergency.

• Its usage is independent of weather and can be operated in cold, damp

wintry conditions.

Disadvantages are:

• Noise from the operation requires the wearing of hearing protection.

• Eye protection should also be worn in the vicinity of the machine while

in operation.

• Appropriate disposal of waste material is required.

• Does loosen surface matrix encouraging the loss of fine materials.

• Cleaning rate is 70% with one run.

• Heavily damages certain asphalt types like antiskid.

• Damages grooves and pavement surfaces over time (8 years).

• Damages sealing.

• Cannot be used to clean AGL.

HPW is most effective on sprayed seals and asphalts that show loss of

texture due to flushed bitumen. This results in safer operating conditions for

pavements.



4.2 TrackJet (Ultra High-Pressure Water blasting)

The TrackJet, an Ultra High-Pressure Water blasting machine

developed by Bernd Weigel in Germany, is widely used at BAA airports and

other leading airports in Europe, as well as European highways for retexturing

and paint marker removal.

Through its modern technology of retexturing, this machine has

consistently removed 100% of rubber build-up and pavement markings from

pavements without touching the pavement micro or macro texture. It utilises a

nozzle system that is truck mounted, applying very little water at very high

pressure through a unique computer-controlled system.

This enables an environmentally friendly and most effective

maintenance for all kind of surfaces. Cost savings through increasing rubber

removal intervals without damaging or destroying the aggregates on the

pavement surface result in an increased pavement life.

Benefits of this technology are:

• Optimum treatment with care of pavement surface.

• Reduces direct and indirect renovation cost by prolonging cleaning and

resurfacing cycles.

• Applicable to all kinds of surfaces; for example asphalt, anti-skid, petro-

grip and concrete.

• Best possible friction values, therefore prolongs the time interval till

next cleaning.



• High environmental compatibility is reached due to very low water

consumption and very low eroded road/runway substance volume.

• No damage to grooving, runway lighting systems, marker paints and

joint sealing.

• Clearing out of expansion joints.

• Only needs one personnel to operate.

• The ease of getting off the runway in the event of an emergency;

runway can be evacuated in 3 minutes leaving the working area tidy and

surface like new.

• Its usage is independent of weather and can be operated in cold, damp

wintry conditions or warm temperatures (2 to 40 degrees centigrade).

• High environmental care due to extremely low water and fuel

consumption; the Track Jet works with clean water without chemical

adhesives and requires only 10 to 20% of the water and 30% of the fuel

HPW systems normally require.

• Low expenses with waste removal, because no chemical is used to

separate the rubber waste from waste water.

This system is also universally suitable for cleaning sealing joints, concrete

renovation, cleaning of steel and concrete areas, apron areas and oil spill

removal.

Disadvantage of systems:

• Appropriate disposal of waste material is required.

• Some airport staff claims that up to 800 m² per hour cleaning (but 100%

rubber removed) is too little.



Various equipments used for water jet system are shown in figures

Fig.3 SUPRA SNOW REMOVAL VEHICLE

Fig.4 UNIMOG 400 L FOR WATERJET SYSTEM

Fig.5 EQUIPMENT FOR WATERJET SYSTEM



4.3 Chemicals

Environmentally friendly chemicals have been developed that

are safe and effective in cleaning rubber from contaminated surfaces. This is

done by spraying the chemicals onto the pavement surface and then scrubbing,

brushing and working them into the rubber deposit over several hours. The

chemicals break down the polymerized rubber into a soft jelly like substance.

The substance is then flushed off the runway by water blasting

when the process is completed. During this process, the runway cannot be

reopened until the process is completed due to the runway surface being

slippery.

The debris cannot be swept up using conventional sweepers

since the chemicals will react with the rubber seals within the sweeper. Even

though the debris is considered to be biodegradable, the chemical is not and as

a result, the usual method of clean up is: flush the soapy residue off the

pavement surface onto the surrounding soil after completion of works.

Over time, the debris accumulates and may eventually cause an

environmental problem requiring remediation. The cost of chemical removal

is usually double the cost of HPW and Track Jet due to the cost of the

chemicals.



Benefits of this method are:

• Rubber is cleaned at the same rate as HPW.

• It softens and removes polymerized rubber.

• The work can be accomplished using airfield staff and equipment.

Disadvantages are:

• Once the process begins, the pavement/runway must remain closed until

clean up is complete.

• It is expensive in comparison to HPW and Track Jet.

• Poses an environmental problem due to chemicals not being

biodegradable over time.

• Time taken for process to be completed.

• Requires more than one personal to carry out process.

• Reacts with rubber seals in conventional sweepers and on runways.

• Large amount of effluent needed to be disposed of.

4.4 High Velocity Impact Removal or Shot Blasting

Propelling abrasive particles onto the runway surface that

blast the contaminant from the pavement surface using Shot-blasting. The

operation is environmentally clean since it is self .contained and the

equipment can be adjusted to produce the desired surface texture result. On a

non-grooved surface it collects the abrasive particles, loose contaminants and

dust from the runway surface. The steel is then recycled for re-use. The

primary reason using this method is for paint removal and the resurfacing and



retexturing of pavement surfaces and not necessarily the removal of rubber

deposits .

Benefits are:

• It retextures pavement and removes rubber deposit in excess of 1,000

m² per hour.

• Retexturing is done by removing a thin layer of the pavement and

coincidentally removing rubber deposits as well.

• The equipment is truck-mounted and can easily be removed from the

runway (like HPW and TrackJet) in case of an emergency landing.

• The equipment cleans the surface while working.

Disadvantages are:

• Expensive to mobilise.

• Overall cost is expensive.

• Noise and vision hazards due to operation process of machine.

• Care is required to carry out machine operation.

• FOD hazard on airfields where steel shot becomes semi-embedded into

the surface and then dislodged later in time.

4.5Mechanical Removal (Grinding or Milling)

Mechanical Removal is generally carried out either by grinding

or milling. Like shot blasting, the primary reason for the machine is not the

removal of rubber from pavement surface.



It is most effective in removing rough patches on highways and

profiling high spots on pavements. It also removes rubber deposits as its

process is carried out.

Benefits are:

• Removes high areas such as bumps on pavement surfaces or at joints

where slabs have shifted or faulted.

• Mills asphalt surface for preparation of overlaying.

• Improves pavement surface friction characteristics by removing a thin

surface layer.

Disadvantages:

• Can cause micro-cracking of the structure leading to accelerated aging

of the surface.

Damages surface texture.



5. Stress Absorbing Membrane Interlayer(SAMI)

Asphalt interlayer system consist of a wide variety of products

and processes, each with unique benefits and specific placement methods to

ensure good adhesion to the underlying pavement. The products may be

classified in a number of categories such as; sand asphalts, grids, nonwovens,

steel reinforcements and SAMIs.

In general, a SAMI is placed on top of an existing pavement and

subsequently capped with a hot mix asphalt overlay (Fig.6).Its purpose is to

delay the propagation of cracking that originates in the pre-existing pavement

that will eventually reflect through to the new surface layers. Cracking in the

surface layers allows penetration of water, salt and other deleterious materials

that can accelerate the deterioration of the entire pavement structure once it

penetrates the aggregate base.

Fig: 6. SAMI within the pavement structure

“A saturated asphalt concrete is typically unaffected

structurally by water unless the asphalt aggregate is stripping prone. In



contrast, a saturated base aggregate loses about 40% of its strength when

saturated.”( source: Pavement Preservation Task Group of Caltrans)

In effect each crack will allow a certain amount of water to

enter the road base hence negatively impacting the original engineered design.

An effective SAMI should therefore; provide additional tensile strength to the

pavement to combat reflective cracking, be flexible enough to allow it to

move within the pavement structure as well as providing a waterproof barrio

for the ingress water from the surface to the pre-existing pavement.

5.1 Stress Absorbing Membrane Interlayer (SAMI) using the FiberMat

process

FiberMatTM is a process that sandwiches strands of chopped fiberglass

between two layers of polymer modified asphalt emulsion, and is applied

using specialized equipment. The first layer of emulsion provides a bond to

the existing hard surface, with random interweaving of the fiberglass strands

providing tensile strength to the mix, the second application of asphalt

emulsion encapsulates the fiberglass, ensures the existing pavement is sealed,

and is quickly covered with a thin veil of aggregate. The aggregate is seated

into this second layer of emulsion using traditional rolling techniques and the

SAMI is capable of accepting traffic in approximately 20 minutes.



This reinforced layer can be used as a temporary wearing surface, on

high volume roads, and is usually covered with a thin layer of hot mix asphalt

within 14 days. Once capped with hot mix, it becomes a true SAMI. Its

function is to seal the existing pavement with a resilient waterproof

membrane, reduce reflective cracking through the new wearing surface, and

ultimately prolong the useful service life of the road.

5.2 Constructing a SAMI using the FiberMat process

FiberMat is a flexible, waterproof membrane that incorporates

asphalt emulsion and fiberglass strands to combat reflective cracking, meeting

all three requirements of an effective SAMI. Patented equipment, developed

specifically for the FiberMat process, ensures even distribution of the

materials and precise computer controls to allow adjustments in application

rates while the machine is in motion.

This equipment is contained within a trailer that houses several spools

of fiber glass, the patented cutter assembly system, an asphalt emulsion pump

and distribution spray nozzles, plus the computer system that controls the

application rate of each component (figure7) . The unit is pulled by an asphalt

emulsion tanker, connecting the output lines of the tanker to the Fiber Mat

machine’s emulsion pumping system



Fig:7. The fiberMat , Application System

The fiberglass strands are pneumatically blown between two separate layers of

asphalt emulsion (figure8) ensuring complete and even coverage of both

fiberglass and asphalt emulsion(figure9).

Fig:8. The fiberMat Application System Fig:9. Even distribution of materials

The even distribution of emulsion and fiberglass is achievable in a

swath up to 4m wide (easily covering an entire lane width).Computer



synchronized nozzles and cutters allow the operator to vary the application

width to accommodate changes in pavement width, tapered sections and

turning lanes. It is possible to place FiberMat as narrow as 1m to a maximum

of 4m (150mm increments)

Fig:10. Application deck, showing separate lines of fiberglass capable of up to 4m width in single pass

To complete the process, it is necessary to imbed a layer of

aggregate in to the second layer of asphalt emulsion. Aggregate is placed with

a traditional chip spreader and seated using pneumatic rollers. The purpose of

the aggregate layer is to protect the newly constructed membrane from

vehicular traffic and construction equipment. The completed FiberMat

(SAMI) is capable of accepting traffic within 20 minutes, and should be



overlaid with hot mix asphalt prior to the onset of freezing temperatures.The

unfinished road, FiberMat and aggregate are shown below(figure11).

Fig:11. Stages of FiberMat application

The entire ‘ train’ of equipment consists of the emulsion tanker,

FiberMat trailer, chip spreader, aggregate trucks and rubber tire rollers(Figure

12).

Fig:12.



5.3 FiberMat Type B

APPLICATION

Specially developed patented machinery chops (60-90mm

length) fiberglass strands in- place and sandwiches them between two layers

of asphalt emulsion prior to the application of a light dressing of 6.35mm size

aggregate, which is then rolled into the surface. The glass fibres are applied at

a rate of 100-140g per m2, depending on the severity of the cracking, with

asphalt emulsion being applied in two simultaneous applications totaling 1.8-

2.3 litres/m2

FiberMat Type B uses the patented FiberDec process, a

combination of special polymer modified asphalt emulsion, chopped fiberglass

strands and aggregate. This mixture act as a highly resilient waterproof

membrane that seals and effectively delays reflective cracking.

This method is superior to other surface treatments as there

are no adhesion problems and the membrane can’t gather or tear because it is

sprayed in place.

FiberMat Type B is also faster to apply than another

conventional SAMI’s. It can be opened to traffic within initial lay-down and

the overlaying of the final wearing course; the latter may even be applied at

later date.



FiberMat Type B has sufficient tensile strength and

flexibility to absorb movements in the pavement structure and can prevent the

pavement from cracking. Where pavement lateral movement of the overlay

might occur(due to cracks in the under laying material) FiberMat Type B

reduces the magnitude of the resulting strain in the overlay by spreading it

over a greater area. While conventional SAMI’s simply relieve stress,

FiberMat Type B acts like a cushion- its thickness absorbs stress, thereby

acting as a true stress absorbing membrane.



6. URETEK’S UNIQUE TECHNOLOGIES (Floor lifting, Soil

consolidation, Void filling)

6.1 Method

After detailed analysis of the problem, we drill small holes to

the appropriate depth above or next to the problem area. Next we inject

specifically developed environmentally friendly material with uniquely strong

and expansive properties.

This material expands at a 100% predictable rate, filling

underground voids, consolidating the soil and stabilizing the surrounding area.

The process can also be used to lift sunken concrete or foundations with great

accuracy; to within a tolerance of 5mm per meter.

All this can be achieved without the need for excavation,

which is expensive and time-consuming.



Fig:13.

6.2 ADVANTAGES

URETEK’s unique technologies are particularly effective and there are

a number of advantages that are not offered by alternative methods.

Universally accepted

These methods are universally accepted by architects, national and

international authorities and are even recommend by insurers

Phenomenal lifting capacity

These methods have a lifting capacity of 40,000 kg per square metre. We

can restore our concrete to full working strength no matter how heavy a load it

supports.



Environmentally friendly

The resins used are without CFCs and can be applied in practically all

circumstances. They do not pollute and do not affect the quality of

underground water. They are even allowed for applications in the food

industry.

Minimal disruption

Fast installation, curing and cleanup equals minimal disruption, Also it

cause minimal dust and noise pollution. After only 15 minutes our material

has already reached 90% of its full strength, so load can immediately be

restored to a treated area.



7. CONCLUSIONS

Runway rehabilitation scheme requires in-depth study of problems of

formulate repair scheme and to choose suitable materials and techniques for

repair. Use of new materials like modern asphalts, SAMI(FiberMat Type B) to

delay propagation of reflection cracks are found to be a lasting solution.

However, its long-term performance in context of Indian climatic conditions

is yet to be established and proven. However, no guidelines are available with

respect to various methods. These are the fields, which needs further studies.

In future, these materials are likely to find extensive usage in highway and

runway work.



8.REFERENCES

Devendra Kumar., “Runway Maintenance Using modern Techniques”,

IRC Journal of Indian Highways, March 2005, pp.31-39

Pawan Kumar and A K Sriinivastave., “Glass Fibre Reinforced plastic”,

Civil Engineering Construction, November 2002,pp.45-50

ICAO Aerodrome Design Manual Part 3

Defence Estates Specification 013 – Marshall Asphalt for Airfields

Website:

www.trackjet.de.


runway resurfacing and repairing using modern materials and techniques

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