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Transportation Industry

A review of foint sealant standards and specifications for aircraft pavements

Road & Transport Research, Jun 2000 by White, G, Allman, M

Abstract

Joint sealant materials for use in concrete pavements have been developed over the last 30 years from bitumen and coal products to corks and, more recently, high performance polymeric materials.

There are many products available with a vast price range, and many foreign specifications and standards exist for their assessment. The lack of an Australian-- specific standard, or the endorsement of a single foreign standard, makes the selection of these materials very difficult, as the common products have not been assessed using a uniform or comparable testing regime. The result is an approach to material selection that is based on personal preference and past experience.

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In an attempt to overcome this predicament, the authors critically examined and compared the various Australian, British and US standards for joint sealant materials and determined that none was satisfactory for aircraft pavement joint sealants in the Australian environment. A specification for the assessment for these materials, which is based on existing specifications and previous research, has therefore been drafted. It is hoped that this draft specification can be utilised to improve the selection of joint sealant materials on a value for money basis.

INTRODUCTION

Joints are commonly placed in concrete pavement structures to allow for thermal expansion/ contraction, shrinkage cracking control, and to allow a break in the construction process. Generally, the upper portion of these joints is filled with a sealant, which serves a variety of functions. Primarily, the sealant is designed to prevent incompressible material (which prevents free pavement expansion under thermal heating) from filling the joint, and to stop fluid (which can compromise the base/subbase integrity) from entering the pavement. Changing technology has seen an evolution in the materials used for joint sealing and the current industry standard is high-performance, cold-applied, elastomeric materials.

A review by the authors of current practice has found that there are very few standards or specifications which govern the long-term performance properties of cold poured materials used for aircraft pavement joint sealing. When this lack of standards is coupled with the range in the performance of available products, it becomes very difficult for a sealant specifier or purchaser to compare different products objectively. The absence of a standard that can be used to measure and compare performance results in a lack of confidence that current materials and techniques are providing the best value for money.

A study of the performance of commonly available joint sealant materials, specifically for RAAF Base Williamtown, was conducted at the University of Newcastle by the authors. As part of that study, a review of standards and practices currently utilised for joint sealing in Australia was performed. This paper presents some findings from that review.

AIRCRAFT PAVEMENT SEALANTS

The sealing of pavement joints provides multiple benefits to aircraft pavements, especially when located in apron or aircraft parking areas. Sealed joints provide:

Protection against incompressibles: Small incompressible objects can become wedged between pavement members and can cause compression failure and spalling on the substrate edges or blow-ups in severe cases (Panek and Cook, 1991).

Protection against water ingress into the joint: Infiltrating liquid may wash away or 'bleed-- out' the fill underlying the pavement. Any washout of base or sub-base material can lead to 'pumping' of the concrete pavement and this can cause major flexural cracking failure (Panek and Cook, 1991).

Protection against ingress of spilt aviation (and other)fuels into the underlying ground: This is an especially important function for sealants used around flight line or aircraft parking areas where refueling occurs and in any pavement where fuel spills are frequent. At a location such as RAAF Williamtown, where the pavement system overlays the Tomago sand beds (a major water source for the Lower Hunter), this becomes even more important.

Prevention of potential foreign object damage (FOD) hazards from entering the joints: If FOD hazards are able to find harbor in the joints, and later come free to be ingested into a jet intake, the consequences are potentially disastrous. Failed joint sealants can become FOD hazards in their own right, which further emphasises the requirement for reliable joint seals.

A barrier to prevent grass and weeds growing up through the concrete from the sub-base: This flora may become a FOD hazard or an obstacle for taxiing and landing/taking off aircraft, as well as detracting from the pavement's aesthetics and potentially adding to the stresses in the joints via root growth.

A uniform and flat surface for the travel of aircraft over the joints: This is more important in areas such as Williamtown, where the joints are quite wide, the aircraft wheels are small and the aircraft travel at high speeds.

Transportation Industry

A review of foint sealant standards and specifications for aircraft pavements

Road & Transport Research, Jun 2000 by White, G, Allman, M

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