Sustainable Steel in Mauritius

STEEL: The Sustainable Construction Solution for Mauritius

Ghunshyam Parsan

CEng MICE MIStructE RPEM

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Table of Contents 

INTRODUCTION ........................................................................................................................... 2 

Sustainability ............................................................................................................................... 2 

Sustainable Construction ............................................................................................................ 2 

Objectives ................................................................................................................................... 3 

STEEL CONSTRUCTION .............................................................................................................. 4 

Steel in Construction ................................................................................................................... 4 

Construction process .................................................................................................................. 4 

Design ...................................................................................................................................... 4 

Detailing ................................................................................................................................... 5 

Fabrication ............................................................................................................................... 6 

Erection .................................................................................................................................... 6 

SUSTAINABLE CONSTRUCTION IN MAURITIAN CONTEXT ..................................................... 8 

A comparison of steel and concrete ............................................................................................ 8 

Re-Use & Recycle .................................................................................................................... 8 

Material Demand ...................................................................................................................... 8 

Energy ...................................................................................................................................... 8 

Flexibility & Useful Life ............................................................................................................. 9 

Off-Site Construction ................................................................................................................ 9 

Health, Safety and Welfare ...................................................................................................... 9 

Water...................................................................................................................................... 10 

Speed of Construction ............................................................................................................ 10 

Supply Chain and Sector Support .......................................................................................... 11 

CONCLUSION ............................................................................................................................. 12 

References ................................................................................................................................... 13 

2

INTRODUCTION 

Sustainability 

Sustainability is the buzz word in Mauritius for the past couple of years and will continue to be so, especially in the context of the Maurice Ile Durable (MID) project. This is arguably the most ambitious project any government has undertaken in our history. And yet, there is a sense of urgency about it, and rightly so. Our very existence depends on the success of this project. The Mauritian Government has shown the political will that has been lacking in the rest of the world so far. But there is only so much the government can do. The private sector has to actively participate in its success, in terms of finance but also in terms of expertise and technology.

The understanding of sustainability has greatly evolved in the past decade. It was initially associated solely with environment and protection of non-renewable resources. But now, it is globally accepted that sustainable development needs to have a much broader perspective, encompassing social and economic aspects as well. The UK Sustainable Development Strategy of 1999(1) defines sustainable development as the meeting of four objectives simultaneously.

1. Social progress which recognises the needs of everyone. 2. Effective protection of the environment. 3. Prudent use of natural resources. 4. Maintenance of high and stable levels of economic growth and employment.

Any plan of implementing a sustainable development programme has to consider all four of these objectives. To achieve this, the government will put in place a Master Plan that will cover the overall development of the country, all sectors included. However, more specific plans have to be developed for each sector, so that implementation can be facilitated. Each individual sector of our economy has to know what they should change in their sector to contribute to the global objectives of MID. It took European countries several years, decades even, to achieve this. We will do better and faster, because we can learn from their experiences and also because we simply have to.

Sustainable Construction 

Buildings account for 40% of all energy consumption worldwide. So targeting this sector is of prime importance. Although most of the energy used by a building is during its operation, it is decisions taken at design and construction stage that influences the level of energy in use. Therefore building design has an important role to play in how efficient the building is for the rest of its expected life span. The choice of construction material and the amount of material used will have an important impact on the overall efficiency of the building. Social, economic as well as health and safety aspects will also influence the sustainable nature of a construction.

Energy is used in buildings for space cooling (air-conditioning), heating, domestic hot water, ventilation, lighting and transportation. These aspects were discussed at length during the recent Green Building Design Initiative workshop organised by the BOI. The design of the building will influence all of these aspects.

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Objectives 

The purpose of this report is to bring to the attention of the authorities some aspects of sustainable development in the construction sector in Mauritius. The report is not an exhaustive study and further studies will definitely be required. However, this report proposes a change of direction that will allow the construction industry to meet the demands of MID and the population at large. Mauritius is at a point on its development path where there will be massive investment in infrastructure. The government has already committed itself to major projects such as Tianli and Highlands. There is therefore both a need and an opportunity to set the direction for the future of the construction industry in this country. This report proposes one such direction in the form of steel construction.

Steel construction is not new in Mauritius. However, it has so far been limited to industrial applications such as power plants, sugar factories etc. Some of the recent supermarkets and retail premises have also adopted steel construction. Among the most popular steel-framed structures in Mauritius are the State Bank Building, Telecom Tower and in a near future the iconic building of Green MCB Building at Ebène. However, concrete is still predominant. This report aims to demonstrate why Mauritius should develop a sustainable construction industry by making use of steel as main construction material. It also aims to show the benefits of adopting innovative methods of construction such as off-site construction.

Concrete is not set to disappear completely. There are indeed several cases where concrete will be the better solution. But the current situation in Mauritius is such that concrete is perceived as the only solution. This report aims to prove that perception wrong. It aims to show how a larger market share to steel will benefit the country, its Maurice Ile Durable project, the workforce of the construction sector and users of buildings at large.

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STEEL CONSTRUCTION 

Steel in Construction 

Structural steel is a descendent of cast iron and wrought iron which were used extensively before 1850’s in buildings and bridges. It is made in blast furnaces at very high temperatures, from iron and carbon. Iron is the most abundant material available on Earth in terms of weight. When mixed with carbon, it produces a ductile material with high tensile strength. It has much better properties than the other two named which made it an instant hit as a construction material. Bridges were the first structures to be made in steel because of its high strength-to-weight ratio that allows it to span great distances unsupported.

Steel is used extensively even in concrete structures. Concrete alone is not very useful for construction as it is very poor in tension. Steel bars are added to the concrete. What is commonly called concrete structures is in fact reinforced concrete, the steel being the reinforcing element, in the form of reinforcement bars (rebars). Such steel accounts for as much as 20% of the concrete.

Steel construction refers to the method of construction that uses steel as the main framework or ‘skeleton’ of the building. The partitions, envelope, slabs and roof can be of different materials. So in a typical multi-storey building, the beams and columns will be of steel. This steel comes in the form of pre-designed, pre-fabricated bars that are simply bolted on site. It accounts for 70% of non-dwelling construction in UK.

Steel is also used extensively as part of the envelope. Insulated sandwich cladding consisting of two thin sheets of steel with a layer of insulation in between has become very popular for the speed and high quality finish. In Mauritius, steel roofing is already quite popular for industrial and domestic markets. Insulated steel roof is only starting to make an appearance in commercial developments.

The floor slabs remain in concrete but even then, profiled metal sheets are used as permanent shuttering and to provide architectural finish. This has been present in Mauritius for quite some time. Profilage has been commercialising its CofraPlus for almost a decade but it is only now that its use is picking up. The use of such metal decking saves up to 40% of concrete in slabs and reduces the amount of rebars by half.

Construction process 

Steel construction utilises off-site construction methods, where the structure is fully fabricated to the nearest millimetre of precision and then simply bolted together on site. The following describes the process of building a typical steel structure.

Design

Following Architect’s conceptual design, a Design Team consisting of Architect, Structural Engineer, M&E Engineer, QS etc do a detailed design. The main objectives of the structural design are to make sure:

1. The building fulfils its intended functions. 2. The building is safe to build, to use, to maintain and to demolish. 3. The building makes economic use of resources

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Figure 1: Design Model

Modern design of steel structures is done by competent professionals using state-of-the-art technology and software. They are helped by a vast knowledge base from a steel industry that invests massively in technical development and dissemination. Specific guidance is available from institutions such as the Steel Construction Institute, British Constructional Steelwork Association, American Iron and Steel Institute, to name a few.

Detailing

Detailing is the process of producing a 3D computer model of the building with details such as member sizes, welds, bolts and holes etc. The model is accurate to the nearest millimetre. This process has replaced the traditional drafting of construction drawings. The modern day drawing office is a team of highly skilled detailers with the latest computer technology at their service.

Figure 2: 3D Detailing Model

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SUSTAINABLE CONSTRUCTION IN MAURITIAN CONTEXT 

A comparison of steel and concrete 

Steel construction is beneficial to all three criteria for sustainable construction: social, economic and environmental. Many of the benefits are reaped immediately at construction whereas some are more long term benefits.

Re-Use & Recycle

Steel is made from iron, which is the most abundant material on Earth. There are 1920 x 1018 tons of iron on Earth (2). There is so much iron on Earth that the Earth acts like one giant magnet. That is why a compass points to North Pole. This iron represents a virtually inexhaustible natural resource comparable to the Sun itself. Steel is also the most recycled material in the world. Steel is recognised for its multi-cyclability. That is, it can be recycled over and over indefinitely without any loss in its properties or quality. Considered globally, 50% of all structural steel are from recycled steel (1). At the opposite end of the spectrum, concrete has almost no recycling potential. It can only be down-cycled into aggregate for roads or landfill. Construction demolition accounts for a substantial part of waste that goes to landfills. With steel construction, construction demolition is entirely recycled into new steel. Steel goes one step further than recycling. Steel can be re-used as is. The component nature of steel structures means that the steel can be dismantled from one building and re-assembled into another. There are several cases where the entire building can be dismantled when no longer required and re-built at another location and given a new life. This is simply not possible with concrete. In Mauritius, structural steel can already be recycled into steel bars using the existing plants at Samlo Steel or Murray & Roberts. Once there is a market for steel construction, these facilities will probably be expanded to turn the used steel into new steel sections for steel construction.

Material Demand

Both steel and cement are imported into Mauritius, either as finished bars or raw materials. However, because of the much better strength to weight ratio of steel, steel structures are significantly lighter than concrete structures, thus requiring less material. This has a knock on effect on several factors. Less freight is required to bring the construction material in. Less transport is required to carry it to site and less storage space is required to store it. Since steel structures are lightweight, the foundations to such buildings require less material and there is less soil excavation required on site. Once the building is demolished after its lifespan, the steel can be recycled in Mauritius and used in another building. Thus, in the long term, the amount of steel imported for construction will decrease significantly. In addition to obvious economic savings, there is a corresponding saving in fossil energy associated with the transport.

Energy

Both steel and cement require energy-intensive manufacturing processes. However, technological progress in steel making has allowed producers such as CORUS to reduce their energy use by around 40% over the last 35 years. On the other hand, cement

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11

construction space and no curing time involved. So as soon as the steel contractor has finished one part of the structure, other trades can occupy that space immediately for M&E, glazing etc. With concrete construction, there is a lot of temporary structures such as scaffolding, formwork and jacks that disrupts the work of other trades. Once the concrete structure is in place, there is a curing and setting time of a few weeks that has to be allowed before the formwork can be removed and the site handed over to the next trade.

In multi-storey construction, this curing time is of particular importance because it determines the speed with which successive floors can be constructed. In steel construction, all the floors can be installed in one go without any time wasted for curing etc.

A shorter construction period has also several other advantages. A short site occupation means less health and safety risks to site workers, less noise, pollution and other disruption to the local community and less construction-related transport affecting the normal traffic.

Mauritius is at the cross roads of development and speed of construction will now determine the speed with which infrastructure can be delivered. Infrastructure building is essential to allow us to continue our economic progress, to deliver a better quality of life to Mauritian citizens and to accommodate a much larger tourist population. The speed of construction may well be the bottle neck that prevents us going as fast as we would wish.

Supply Chain and Sector Support

Because steel is the first choice of the developed world, there has been a lot of investment in research and development in these countries to make steel construction more efficient. A number of structural solutions have been developed to cater for the various building needs, such as long-spanning systems, service integration, fire protection, shallow construction, acoustics, dynamics etc. There is a vast wealth of information disseminated by the steelwork industry worldwide. Adopting steel construction allows us to benefit from all this work that has already been done.

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CONCLUSION 

Steel construction may be relatively new and innovative in Mauritius but it has been the mainstream construction method in most developed countries for a long time. We can learn from practices in these countries to adapt steel construction to Mauritian needs to deliver high standard infrastructure that meets social, economic and environmental aspirations of Maurice Ile Durable.

This report has given an overview of the various benefits steel has over concrete:

• Recyclability of steel • Lower material demand from overseas • Lower levels of energy consumption during construction and during lifespan of the

building • Flexibility and extended lifespan of the building • Re-use and retained market value of the material after lifespan of the building • High quality, low waste off-site construction • Speed and economy of construction • Enormous saving in water usage • Better health and safety standards • Better welfare of construction workforce • Benefit from state-of-the-art technologies from developed countries.

Steel construction will not pick up on its own in Mauritius. Private sector developers may not have the will or the time to try new methods. Architects and engineers in the private sector may not have enough incentive to try innovative structural solutions, except for prestigious projects such as the upcoming iconic Green MCB building at Ebène, designed by Architect Jean Francois Koenig. Developers and professionals alike will be much more at ease with steel construction if they witness its use on a larger scale by ‘others’ first. For all the reasons evoked above, that ‘others’ will have to be the government. It is the government that has to take the lead and show the way by utilising steel construction on public building projects.

13

References 

(1) A Better Quality of Life – a Strategy for Sustainable Development for the United Kingdom,

Department of the Environment, Transport and the Regions, London, 1999. (2) www.sustainablesteel.co.uk