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An extensive desk study identified seven groups of technologies with potential to reduce the carbon footprint: secondary cementitious materials modified Portland or non-Portland cements, low cement concrete, ultra high strength concrete changes in Portland cement (PC) manufacture, alternative binders and carbon capture. A short list was produced of three constituents with potential for high CO2 reduction and suitability for construction in UK.
With the help of literature reading and previous works on this low carbon concrete constituents, Asphalt, GGBS and Geopolymer are screened and taken for further detailed study for their CO2 emission and availability in the UK.
These three candidates were studied in detail for their carbon dioxide emission, availability, environmental impact and construction issues. The CO2 emissions associated with manufacture and transport of the materials were calculated and recommendations made for their future development.
The sample was selected through judgment selection methodology where the research sample based on a certain criterion. As discussed earlier that the construction industry becomes all the more complicated in light of the new alternatives, environmental issues and the economics involved.
Compare the different seven types of concrete with their co2 emissions during the various processing.
The observations made in this process are tabulated and statistically analysed for reaching an outcome.
Comparison of CO2 emission from Low carbon concrete constituents with conventional concrete to find the percentage of carbon dioxide reduction.
The case studies about the projects in UK where low carbon concrete constituents used are helped to analysis the availability and their opportunity to use in current construction industry.
Chapter 4: Case Studies
4.1 Usage of ground granulated blast-furnace slag (GGBS) in White River Place, St Austell, UK:
The White River Place Development scheme aimed to renovate a brownfield site into a stimulating town centre for St Austell and was proposed to account for £75 million. The town centre is a seven storey building featuring a blend of uses involving offices, food and catering, cinema theatre, retail and a car park for about 550 cars.
The South West Regional Development Agency (SWRDA) partly sponsored this development scheme in St Austell and as per the contract; the objective of the program was to achieve BREEAM Very Good. BREEAM is the world's foremost environmental assessment method and rating system for buildings, with 200,000 buildings with certified BREEAM assessment ratings and over a million registered for assessment since it was first launched in 1990 (BREEAM, 2012). But SWRDA and the joint venture client White River Developments dreamt big and aspired to achieve BREEAM Excellent, and Sir Robert McAlpine then shared the contract.
4.1.2 Overview of Environmental Features
The team and the client worked very wise with the available credits. Instead of implementing elements that could incur more expenses, they put efforts in attaining all the available credits. They,
Maximised the materials credits with effective procurement and awareness of issues,
Used local labour and materials,
Harvested the rainwater and very efficiently used the water,
Implemented effective ecological input on a brownfield site,
Made the Parkmark compliance for the car parking compulsory,
Implemented environmental policies and management.
4.1.3 The BREEAM Assessment
All the required information was provided to the team by the BREEAM Assessors who collected and coordinated the information from the outset. By opting for this way, the project scored considerably high in Land Use and Ecology, Materials and Waste, Transport and Water. The Management section was accessed full score by using exemplar construction processes, commissioning and environmental procedures.
The BREEAM Assessment was a paramount part of project meetings and continued to be one throughout the project, allowing the principles of the guidance to be reviewed and implemented at very early stages so that they could not impact the cost or programme in any negative possible manner.
4.1.4 Building Services
The mechanical and electrical strategy was designed from the outset with economy and sustainability in mind, but not at the expense of functionality or comfort. One of the biggest challenges was the use of passive technologies in a busy town centre like this. The technologies were employed wherever possible, but were augmented by low carbon products with higher efficiencies such as heat pumps. On one hand, where the large expanse of roofing implied that the water accumulated on the roof during rain was to be attenuated to control the flow into the drains, on the other hand, it was an opportunity to provide a large rainwater harvesting system, which would provide free water for use, both in the landlord areas and for irrigation, for washing-cleaning and to individual tenant premises. Carbon monoxide sensors were linked to pulse fans in the car park which would run at low speed when required to provide fresh air. These fans were also linked to the smoke control system and when the fire alarms were activated, could be used to create safe fire brigade access.
4.1.5 CO2 footprint
The main contractor had ISO 14001 EMS systems and very high ISO standards set for environmental management on site. A dedicated environmental manager was also deployed on site throughout the contract tenure.
As major town centre site, liaison and community interaction and involvement were important and considerate contractor scores were very high. It was essential to make sure of the responsible sourcing. For this reason, the sub-contractors and suppliers were interrogated about the environmental credentials of materials used. It was proposed that, during construction, sustainably sourced materials (including a high content of recycled material) will be used wherever possible and all major building elements having a Green Guide 'A' rating will be used.
Along with Concrete, ground granulated blast-furnace slag (GGBS) was used which meant that the slabs were not required to be major load bearing. Thus there was a reduction in the CO2 emissions associated with concrete. The stones used were locally available, bricks came from neighbouring Devon and concrete blocks were sourced from St Austell. Slightly damaged blocks were used for areas of the building where finishes allowed saving some 60 skips worth of construction waste. The plans specified Western Red Cedar timber from South West England, rather than Canada. A green transport plan was created and a strong pedestrian link was incorporated in the design to encourage movement throughout the town centre.
All jobs, major and minor, associated with the project were advertised locally, and a local training and education programme was operated, with weekly visits for GCSE, ONC and HNC construction students. Apprentices as well were employed across the site.
4.1.6 Project Team Details
Client: White River Developments Ltd,
Architect: Chetwoods Architects,
Developer: Sir Robert McAlpine Ltd,
Building Services: Hulley& Kirkwood,
PM/QS: HCD Management,
BREEAM Assessors: GBSPM Ltd/TPS Consult