Jackson recently won a design and build contract to construct new flood defences in Newhaven, East Sussex, for the Environment Agency.
This project covers both banks of Newhaven, including the commercial areas near the port, and has a total scheme value of £17m.
The design includes earth embankments, concrete walls and flood gates to protect 431 homes and 387 businesses in the area. The project also includes a temporary flood gate over an existing railway line, and a demountable flood barrier which can be quickly deployed across the highway during a significant flood event.
Construction will begin in November 2016 and is scheduled to finish in 2019.
67% carbon reduction in concrete is a UK first
Jackson Civil Engineering has achieved a 67% reduction in CO2 by using a new type of ‘cem-free’ concrete on a flood defence project in Woodbridge, Suffolk, for the Environment Agency.
This is the first time this concrete has been used in the UK commercially, and the potential for reducing carbon emissions on future construction projects is extensive.
Concrete is a significant contributor to the carbon footprint of the construction industry. The concrete ordinarily used on this type of flood defence project consists of 50% GGBS and 50% Portland cement, which has a typical CO2 value of 158 Kg per m3. In comparison, cem-free concrete is made up of 95% ground-granulated blast-furnace slag (GGBS) and a 5% alkali activator, and has a CO2 value of 52kg per m3.
Although not suitable for all applications, the cem-free concrete was successfully used as an infill in a 265m section of flood wall. This amounted to 51 cubic metres, about 35% of the total concrete used, which achieved a CO2 saving of 5 ½ tonnes. To put this in perspective, it would take five acres of forest one whole year to redress the balance of this carbon output, using the traditional material.
Pro’s and cons
As well as the potential for significant carbon savings, cem-free concrete has better long-term durability, produces less heat in the reaction, making it more suitable for large pours, and requires fewer expansion joints.
There are, however, some minor drawbacks, which make it unsuitable for some applications. For example, during the trials the material did not respond well to floating, which made it unsuitable for use in the floor slab, although with work on the mix design this should be overcome.
The curing time is also slower, which means that shuttering would have to be left for a day or two longer than usual. However, on the right project, with sufficient programming this issue could be overcome.
Jackson’s Project Manager Ashley Tate said: “Over the course of this project, we’ve learned a great deal about the suitability of cem-free concrete going forward. On the right project, and with the correct planning, this material has the potential to generate significant carbon savings for construction.”
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Jackson is currently upgrading nine weirs along the Thames under a design and build contract for the Environment Agency.
The project involves replacing up to 40 weir gates, and installing new head gear, control kiosks and handrailing to five of the weirs. The team has also designed and installed new fish and eel passes on three weirs.
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Jackson has picked up one gold, one silver and two bronze Considerate Constructors awards for projects across the country.
There are over 8000 sites registered with the scheme, which aims to encourage best practice, and improve the image of the construction industry. In 2016, the scheme gave out 173 gold, 293 silver and 430 bronze awards.
Jackson’s Gold award went to the Sandwich Town Tidal Defence Scheme, which was a complex project on the River Stour Estuary involving the creation of 14km of flood walls, a new tidal relief area and a separate flood wall in Sandwich town centre.
The judges commented: “The site team not only managed its environmental obligations to an exceptional level, but took a pro-active approach by engaging the community in protecting the eco-system and creating new habitats. Principal among these was the creation of a new woodland area, helped by schoolchildren planting the saplings. More than 3000 reptiles were transferred to new habitats and the regular publication of achievements in protecting and enhancing the environment supported this community teamwork approach.
On this high-profile public-interest project the site maintained exemplary standards of presentation throughout, with all aspects of appearance helping to promote a positive image of the industry, and contributing to a lasting impression of considerate construction.”
Silver went to Kingsman Farm in Hullbridge, and Bronze went to the Kings Lynn Tidal Revetment project, and the A12-A143 Great Yarmouth Link Road.
Jackson has been shortlisted for four Considerate Constructors National Site Awards.
Sites at Kings Lynn, Hullbridge, Great Yarmouth and Sandwich have all been recognised by the scheme for excelling in five main areas: community, appearance, environment, workforce and safety.
As well as engaging with local schools, the Jackson site teams engaged with the local community. For example, at the Sandwich project, during a tidal surge the site team worked with personnel from Dover District Council and members of the public to fill and distribute over 500 sandbags in a 12 hour shift, thus averting a crisis. It is pertinent to mention that at this point, the flood defences were still under construction. Subsequent tidal surges have proven the success of the completed defences!
The National Site Awards recognise sites that have raised the bar for considerate construction, by looking at the measures a site has put in place to be more considerate towards local neighbourhoods and the public, the workforce, and the environment. The three awards will be presented to the site teams at the end of April.