The major requirements of the surface of an airfield pavement are to provide:
- Excellent Friction Characteristics
- Comfort rideability
- High Strength and stability to withstand the shear stresses induced by heavy wheel loads and high tyre pressures.
- A durable ,hard wearing weatherproof surface free from loose material and sharp edges that might endanger aircraft.
- Resistant to Fuel spillage and Jet blast.
- Facilitation to economic maintenance
- The relative importance of the above requirements depends on the use of pavement, over the years concrete pavements has achieved all of the above functional requirements for a wide range of airfield applications at major international airports, domestic airports, airforce stations and general aerodromes.
Although Concrete Airfield pavement structural behaviour and failure mechanism are similar to Concrete roads, there are some major differences in loading and performance requirements including:
- The magnitude of the loading, upto 30 tonnes per wheel.
- The configuration of the loading with upto 28 wheels in an undercarriage, with wheels in groups of upto 8 on a main wheel gear.
- Tyre pressure will reach 15 bar and 31 bar on airforce aircrafts.
- The number of loadings, generally less than 1 million in the design life, rather than potentially several hundred million for major roads.
- Requirements of pavement durability. Loose material can cause what is generally known as foreign object damage (FOD) in particular to Jet Engines with potentially catastrophic consequences for aircraft and within a fraction of seconds the aircraft can be in ashes.
- The implication for airfield pavement design is that there are two unknowns, the load and the number of load repetitions, whereas in road design the load is basically fixed as standard axle and only the number of load repetitions varies
STP’s offering for Pavement Construction Techniques
Slipform Paving – Airfield Pavements which are also called PQC Pavements is optimised for paving via slipforming. Selection of the right Concrete admixture is very important as the Concrete Pouring Time is critical and delivery rate is calculated to minimise waiting time on site. The rate of supply of concrete must match the placing rate to ensure consistency in the timing of placement, compaction and finishing processes. STP offers ShaliPlast PQC,high performance superplasticiser based on Napthalene formaldehyde and ShaliPlast PCE, Polycarboxylate ether based high performance plasticisers which gives the required workability and Strength to the Concrete.
Joint Cutting of PQC Panels – Initial Joint cutting of PQC Panels should be done within 24 hours of Pouring and Final joint cutting is carried out after 28 days followed by Sealing of Joints with Shaliseal PU 2K, Two component Elastomeric Polyurethane joint sealant or Shaliseal PU, Single component Polyurethane joint sealant having properties of Jet fuel resistance and confirming BS 5212 specifications with MAF of (-) (+) 30 %.
Curing – Effective curing is required to develop required properties in the hardened concrete. Abrasion resistance is particularly sensitive to the early drying of the surface that may occur if curing is inadequate. The early strength development of concrete containing gobs is slower in cold weather. So proper curing is important to prevent moisture loss, which may result in surface dusting and poor abrasion resistance. It is therefore important to use curing compounds with maximum curing efficiency. STP has been able to innovate a resin based Curing compound Shalicure AL SB which offers curing efficiency of up to 90 %.
Aftercare – An assessment of structural condition might be needed during the life of a pavement for monitoring its rate of deterioration, calculating residual life and planning future maintenance requirements. For Existing pavements or new pavements quite often we come across problems like
- PDR / Surface Cracks / Crazy cracks on Pavement Panels
- Edge Spalling of Pavements
- Major and minor pot holes or Pug Marks
- Patch resurfacing requirement
- Nose wheel Area repair.
- Any other concrete damage which may lead to FOD issues.
STP has been able to develop ShaliPatch EC, Elastomeric concrete technology which can provide permanent repair solution to Concrete Pavements and the pavement can be back in service within 1 to 2 Hours.