Following permission being granted for the redevelopment and extension of Nottingham’s tram system that included substantial investment, the city and surrounding areas were set to benefit from an extension to the tram system that was more than double its original size.

In total, 17km of additional track would extend the tram system to the south and south west of the city including Chilwell, Beeston, Clifton and Wilford, providing passengers with a direct link to national train services.

With the development set to introduce two new transport lines, the city of Nottingham and the outlying towns and villages of Nottinghamshire would benefit from a reliable and efficient transportation network capable of delivering 23 million passenger journeys each year. To accommodate this, an additional 28 tram stops were created, taking the total number of stops to 51.

With a substantial requirement for a number of specialist concrete mixes, alongside a variety of bespoke paving and kerbing solutions, contractor Vinci Construction identified Aggregate Industries as the ready mix and precast concrete partner that could deliver flexible processing and supply methods to meet demand.

Mix and match solution

Alongside a need for visual and performance uniformity throughout the project, there was a task to be done on achieving agreement from all parties, including Vinci Construction and two councils on various specifications including the colour and concrete design.

Each party brought to the table very specific ideas of how certain tram stops should look in accordance to its individual surroundings, as well as 17km of tram line that would run across the town of Nottingham. It was up to Aggregate Industries to identify a palette of products which could be used in a variety of sections – delivering both a resilient and visually appealing finish.

Aggregate Industries was appointed early on in the process to supply a portfolio of its Charcon paving materials, as well as the products and services of their Ready Mixed Concrete division. With innovative and cost saving solutions that could be used to build and renovate a number of bridges on the development, as well as to complete the concrete elements of the track itself, Vinci also awarded the supply of specialist ready mix concretes to Aggregate Industries.

Building bridges

The wider infrastructure changes to the new tram line extension included the creation and redevelopment of four bridges. The pre-existing bridge structures needed to be widened and reinforced with new concrete road surfaces, which would mean extensive and costly changes to the piling of each bridge.

Aggregate Industries’ product recommendation was Lytacrete – a specialist lightweight concrete using Lytag secondary aggregate, which can be up to 40 per cent lighter than traditional comparable materials.

Therefore Aggregate Industries was able to reduce or eliminate the need for expensive repiling works and deliver a significant cost reduction on the redevelopment and creation of all four bridges.

Furthermore, Aggregate Industries was able to refine the Lytacrete manufacturing process to produce a mix with lower density than usual. Traditionally, Lytacrete is produced with an oven dry density of 1800kg but, in order to correctly meet the weight-bearing capacity of the bridges, a density of 1450kg per cubic metre was required. This was achieved through the use of both Lytag course and fine material being used in the concrete mix.

In total, 1,600 cubic metres of Lytacrete was supplied for the completion of all four bridges throughout the tram development.

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A colour match to suit

8,000 cubic metres of Articimo Exposed concrete was also supplied, which was used as the finished surface in-between and around the tram track, as well as in larger pedestrian areas such as the popular Queens Walk in the centre of Nottingham and at the majority of the 28 new tram stops.

Articimo Exposed is part of a range of decorative, exposed aggregate and through- coloured ready-mixed concretes which, for this project, offered the designers a broad pallet of visual possibilities in both texture and colour. The surface was achieved by placing the concrete in a conventional manner and retarding the surface of the concrete in order to allow for the removal of the top layer of skin at a later stage.

The removal of the outer ‘skin’ of cement paste uncovers a decorative coarse aggregate underneath. Due to its decorative finish, contrast with other materials, durability and skid resistance, the exposed aggregate finish was ideal for this type of application.

Using the same base mix, the company supplied a choice of decorative concretes in three colours – Golden Flint, Articimo Midnight Dark Granite and Articimo Non-Pigmented Light Granite.

The pigmented mix was colour-matched to the adjacent asphalt and laid as nibs directly next to the tram track itself, to provide a durable surface that would resist the vibration of the transport system – a more effective solution to block paving and asphalt in this setting. Articimo was also specified, not only to reduce ongoing maintenance on the line, but also to improve skid resistance for cars travelling over the rails – especially during wet weather.

The process of developing the right colour- matched product took approximately eight months and included a variety of field tests, laboratory samples and full site trials, with the final products requiring full approval from all parties.

Pedestrian friendly

Aggregate Industries turned to its Charcon division to supply a suite of pedestrian walkway surfaces which consisted of complementary paving materials that could offer durability, affordability and aesthetic appeal in abundance.

The Charcon team worked closely with project decision makers to devise a palette of materials that ensured a uniformed visual appearance to all of the 28 new tram stops, whilst allowing each council to meet its own design requirements with unique laying patterns.

With a total of five products offering a variety of practical and visual benefits, Aggregate Industries was able to meet the needs of both councils, especially when it came to its steel or fibre-reinforced flag paving – Charcon Ultrapave.

Ultrapave, whilst boasting the appearance of natural granite, provides the ideal reinforced solution for high volume urban paved areas that require a durable pavement which reduces the potential of trip hazards and fractures from vehicle run-over.

In total, two variations of Ultrapave textured paving were supplied in dark grey and silver grey colourways, covering 23,065 square metres across the breadth of the development. In addition, 6,588 square metres of Woburn block paving, which consists of a rumbled and weathered appearance, was supplied alongside a substantial amount of premium quality Charcon Andover flag and block paving and a considerable quantity of Tactile paving, a regulation-compliant surface solution to assist visually impaired pedestrians to identify hazards.

Lastly, the dedicated team was asked to create a bespoke kerbing solution that matched the colour, texture and durability credentials of its popular premium Charcon Appalachian product. Combining uniquely formulated granite aggregate for inherent durability, Aggregate Industries was able to use the same Appalachian mix to form 6, 588 square metres of kerbing for all 28 of the new tram stops.

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Ticking all the boxes for functionality, appearance and cost efficiency, this suite of products offered itself to a choice of laying patterns which suited the differing requirements of the two councils.

Just in time

With such large quantities of both Lytacrete and Articimo on a rolling, just-in-time delivery plan, Aggregate Industries ensured they made efficient use of its nearby Nottingham and Mansfield processing plants to help process and develop the suite of bespoke products. Quality control was ensured at all time to prevent any cross-contamination or logistical issues for these specialist concrete products.

Vast modifications were also made to improve the production facility in Nottingham including the creation of an additional aggregate storage bin to meet Vinci Constructions’ requests. In addition to this, a dedicated logistics manager was appointed to specifically manage the product and delivery complexities of the Nottingham Tram Project. With the majority of raw materials used in the concrete being supplied by Aggregate Industries, there was an additional task to seamlessly deliver the logistical requirements and meet challenging concrete demands of this project.

With the tram line being divided into 30 sections, each with its own engineer, Aggregate Industries played a critical role in educating engineers on the different type of concrete they would require for their section of the track, as well as devising a simplified ordering system which would minimise any confusion when ordering different shades of Articimo.

Collaborative approach

From the specialist and collaborative product recommendations, to the logistical nous of the delivery drivers, Aggregate Industries worked tirelessly to meet every challenge head on in order to comply with what was a challenging specification across both the hard landscaping and Ready Mix Concrete elements of the project.

Completed last year, the Nottingham tram extension showcases the company’s ability to collaborate and solve real construction problems with an intelligent combination of industry knowledge, manufacturing skill and a true dedication to timely supply and still remains as Aggregate Industries largest job to date using its Articimo concrete range.