Waitrose National Distribution Centre, Bracknell

Client: Waitrose Ltd. Project: 3,000sqm internal new build, phase 1, and 200sqm external refurbishment, phase 2. Main contractor: Moss Construction Ltd. Also on site: WT Construction Ltd, phase 1, and Tarmac National Contracting Ltd, phase 2.

Overview

The system was specified by the client for a new high bay warehouse at their National Distribution Centre in Bracknell, Berkshire. The project comprised 3,000 square metres of internal new build required to carry 100kN rack leg loads for racking systems, and a 200 square metre external refurbishment area over an existing concrete slab.

The requirement

A high bay warehouse floor has to carry concentrated point loads from rack legs without cracking or settling, and hold tight surface tolerances so racking and handling equipment sit true.

Why grouted macadam

On new build the reduced depth of the overall construction, a consequence of the high stiffness of the material, means less preparation is needed. A single jointless slab is completely impermeable to chemicals and fuels, can be used as a walking platform for construction traffic, is less weather dependent than concrete and can be patch repaired.

It can be left in its natural finished state for light industrial use and offers a variety of surface finishes, with no additional surface finishes required.

On the external refurbishment phase, overlaying saved excavation and disposal of the existing surface, added to the structural integrity of the pavement and allowed the works to be completed quickly.

Design and specification

Phase 1 comprised 40mm of surfacing, a 10mm regulating layer and 150mm of cement bound material with seven days of curing, onto a Type 1 layer of stone achieving a 30 per cent CBR reading as a suitable construction platform.

Phase 2 was to plane off the existing area to tie in, apply a heavy tack coat, regulate as required and install 40mm of surfacing.

Installation

Works were carried out with main contractor Moss Construction Ltd. The supply and lay of the basecourse and open graded asphalt materials was subcontracted to WT Construction Ltd, who laid the open graded asphalt with a Laserpave machine to achieve a surface tolerance of plus or minus 3mm over a 3 metre edge.

The asphalt specification required a 10mm aggregate size to achieve a 25 to 30 per cent void ratio, rolled with a dead weight roller and no vibration to ensure minimum compaction. It was laid at circa 160C and cooled to 30C before the microsilica mortars were flooded through the matrix and spread evenly with rubber squeegees.

The planing works in phase 2 were carried out by Power Plane Ltd, with Tarmac National Contracting Ltd providing the open graded asphalt.

Outcome

The completed areas were ready for trafficking within 24 hours.

Archive photographs from the original CIP project records. They survive only as small thumbnails, so they are shown here at their original size.

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.