Arriva Bus Depot, Thurmaston, Leicester

Client: Arriva Fox County Ltd. Project: 5,500sqm external refurbishment, 2001. Main contractor: Civil and Industrial Products Ltd. Subcontractor: Jarvis Highway Maintenance Ltd. Engineers: MD Prosser Associates.

Overview

Arriva Fox County Ltd, one of the UK's leading bus operators, specified grouted macadam to refurbish their bus depot at Thurmaston in Leicester in 2001. The depot is busy and heavily trafficked by buses and lorries, being shared with a transport company.

The requirement

The existing concrete slab had badly deteriorated. There were many undulations, and areas that had completely broken up needed reconstructing to the full depth of the existing construction. The depot had to keep running throughout.

Engineers MD Prosser Associates approached CIP about the system after receiving technical literature on it.

Why grouted macadam

The options were restricted. A complete new concrete slab meant digging out and disposing of the existing surface, then at least seven days of curing before the area could be trafficked, which would have caused significant disruption to depot operations.

An asphalt overlay would have been quicker than either concrete or grouted macadam, but asphalt would not deliver the resistance to rutting, the durability or the fuel resistance the depot needed.

Grouted macadam gave a fast programme with minimal disruption, a fuel resistant and jointless surface, and 24 hour curing, in a pavement specification that would not rut or deform under continuous bus and lorry movements.

Design and specification

For the overlay areas the proposal was to plane off to tie in with existing levels, crack and seat the existing concrete slab, regulate as required to take out undulations, then overlay.

Cracking and seating matters when overlaying concrete. The dominant character of the material is the microsilica cementitious grout, and its performance characteristics are those of a higher specification concrete. Overlaying directly onto a rigid slab without de-stressing it risks reflective cracking, so the existing surface is cracked and seated to transform it into a semi flexible base.

The reconstruction areas, around 900sqm across six patches, were dug out down to the sub base, recompacted and built back up with a heavy duty macadam basecourse and the surfacing on top.

Installation

The works were carried out in four phases to allow the client to keep operating, and were completed in one continuous visit to site. The overall programme from start to finish was three weeks.

Outcome

The depot remained operational throughout. The programme advantages were significant for an operating site, and the surface has performed well since installation.

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.