Newham Bus Holding Area

Client: Newham Environmental. Project: 400sqm plus 110sqm external refurbishment. Main contractor and subcontractor: John Crowley Ltd.

Overview

The brief was to dig out and reconstruct a 400 square metre bus holding area with a new build design, including four bus bay areas finished in red to highlight the parking bays. Buses stand in the area every quarter of an hour.

The requirement

The works had to be completed in four to five days with minimal disruption to a busy public area. Bus areas need durable running surfaces that will not deform or rut under continuous vehicle movements, and fuel resistance is a critical requirement.

John Crowley Ltd are term contractors for new and refurbishment projects for numerous London borough councils. They approached CIP for technical information and were satisfied the system would meet their surface requirements.

Why grouted macadam

Newham Borough Council was receptive to the jointless system. On price there was no competition against the traditional specification of jointed concrete, which would have taken circa six to seven weeks. The system was therefore an advantage on programme as well as on performance.

A presentation was given to Crowleys and to Newham to introduce the system formally and discuss its suitability in greater detail, after which Newham gave the go ahead.

Colour was the other factor. Finishing the four bays in red marked them out permanently in the surface rather than relying on paint that wears off under standing buses.

Design and specification

The new build design to replace the existing concrete slab comprised 40mm of surfacing, 60mm heavy duty macadam basecourse and 150mm heavy duty macadam roadbase onto 250mm of Type 1 sub base. The design was based on a CBR value of 5 per cent and a traffic flow of 2 million standard axles per day.

The system was guaranteed at the time not to form cracks greater than 5 millimetres, not to deform, to be resistant to skidding of vehicles, not to spall due to frost, and to remain bonded to the sub base layer over a 12 year design life.

Installation

Works commenced on site on 26 July 2002 and took an overall programme of four to five days including a 24 hour curing period. John Crowley Ltd supplied and installed all basecourse, roadbase and wearing course layers under the supervision of CIP contract management.

The open graded asphalt has to meet a specification before the mortars are poured through it. It needs to be laid with a 10mm aggregate size to achieve a 25 to 30 per cent void ratio, and rolled without any vibration to ensure minimum compaction. The CIP specialist installation team then installed the mortars through the asphalt matrix using rubber scrapers.

Outcome

The area was handed back inside the four to five day window, against the six to seven weeks a jointed concrete solution would have taken, with the bays permanently marked in red.

Photographs from the original CIP project records. The system was supplied under the Densiphalt name at the time of these works and is now supplied as Confalt through Contec. This was a CIP installation, and the grouted macadam contracting capability now sits with Globe Civil Engineering.