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Geosynthetics for UAE Road Contract

Online since 28.06.2018 • Filed under Professions - Construction & Contractors • From Issue 24 page(s) 42
Geosynthetics for UAE Road Contract

A specialised geosynthetic interlayer product was specified for asphalt reinforcement on the Sheik Mohammed Bin Zayed Road which heads 70km NE from Abu Dhabi.


Once the asset management system of the nation’s Ministry of Infrastructure Development had assessed the global success of specialist geosynthetics in pavement reinforcement, Kaytech’s SealGrid 100/100 was nominated as a pilot project on the most deteriorated 12km stretch of the Sheik Mohammed Bin Zayed Road, a very busy route that required a quality upgrade. The project was undertaken by Fala Road

Contracting. Traffic assessments of the road showed an average daily traffic count of 30 000 inter alia 2 000 heavy vehicles (axle weight < 20 tons) per day, were causing considerable stress on the slow lanes. Pavement condition analyses revealed severe fatigue, including reflective cracking, deflections and surface distress. A 3km section of the project chosen for a SealGrid upgrade displayed rutting, cracking and significant deflections under load.

 

SealGrid consists of high strength glass fibre roving, knitted to a paving fabric to form a reinforced composite geosynthetic that was rolled out over a SS1H, slow-setting grade of emulsion tack coat layer. The hot mix asphalt (HMA) was set at 4-8% voids with an optimum binder content of 3.6-4.0% comprising a 60/70 penetration grade bitumen. Compaction was based on a bulk specific gravity of 2.554-2.575 Gmb. The reinforcing effect of the low strain glass filaments in combination with the waterproofing, stress-relieving and bonding properties of the paving fabric leads to a dramatic reduction of reflective cracking under asphalt overlays. SealGrid is unaffected by most chemicals and, importantly for location of this project, can withstand extremely high temperatures.

 

Key considerations

• Rolls of SealGrid were stored and handled carefully to avoid any contact with solvents that may affect adherence to the tack coat.

• Uniformity of the milled surface to ensure consistent distribution of the tack coat and prevent damage to layer which should be clean milled for proper saturation.

• Ensuring a uniform distribution of tack coat (one litre per square metre) over the milled surface. Add bitumen to highly porous and cracked if needed.

• Keeping the tack coat undisturbed prior to installation, ensuring optimum adherence of layer.

• Timing of laying SealGrid before, during or after curing. Tack coat depends on the grade of bitumen being used. Polymer modified emulsion is preferred.

• Attend to overlaps by manually applying tack coat between and over the joints.

• Apply a binding layer of asphalt by shovel in front of the truck wheels to avoid disturbing the layer. A year on, inspections of the road revealed that 95% of the 12km pilot project, including the Sealgrid section, is performing as per expectation. The product can reduce traffic-induced crack propagation by a factor greater than seven. Surveys done in the ensuing years should prove a calculated savings cost of approximately 30 to 40%.

 

Kaytech

W www.kaytech.co.za

Issue 24

Issue 24

July 2018

This article was featured on page 42 of
To Build Magazine Issue 24.

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