Sustainable development and climate change initiatives
Introduction
Sustainable development has been defined by the World Business Council for Sustainable Development (WBCSD) as: “Forms of progress that meet the needs of the present without compromising the ability of future generations to meet their needs” [1].
The WBCSD continues: “Given the scale of world poverty today, the challenge of meeting present needs is urgent. But we must look ahead and do our utmost to ensure that what we do today for our ever-growing population does not compromise the environmental, social and human needs of our descendants”.
Concretes made with hydraulic binders (almost all based on Portland cement) are by far the most widely employed construction materials worldwide in terms of volume, and as such have a huge impact on the environment and also on sustainable development. Produced using readily available raw materials, being easy to use and possessing good strength and durability, concrete is indispensable for meeting modern society's needs for infrastructure, industry and housing. The fast growth in developing economies such as China or India can only be sustained if an inexpensive construction material with low environmental impact is available. Concrete fulfils these requirements.
In the present paper we argue that the cement and concrete industry is contributing positively to the Climate Change Initiative by:
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Continuously reducing the CO2 emission from cement production by increased use of bio-fuels and alternative raw materials as well as introducing modified low-energy clinker types and cements with reduced clinker content.
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Developing concrete compositions with the lowest possible environmental impact by selecting the cement type, the type and dosage of supplementary cementitious materials and the concrete quality to best suit the use in question.
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Exploiting the potential of concrete recycling to increase the rate of CO2 uptake.
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Exploiting the thermal mass of concrete to create energy-optimized solutions for heating and cooling residential and office buildings.
Much scientific evidence links climate change to greenhouse gas (GHG) emissions of which carbon dioxide (CO2) ranks amongst the most important, accounting for 82% of the total. It is estimated that the cement industry produces approximately 5% of global manmade CO2 emissions, but it emits almost no other GHGs. When all GHG emissions generated by human activities are considered, the cement manufacturing industry is found to be responsible for only about 3% of total anthropogenic GHG emissions.
Apart from emissions linked with the energy used for clinker burning, grinding and other operations, there is a natural release of CO2 associated with the de-carbonation of limestone to give the calcium silicates and aluminates in clinker. This “Raw Materials CO2 Emission” is roughly equal to 0.53kg per kg of clinker. The total CO2 emitted in cement manufacture includes, in addition, the “Fuel-Derived CO2” and also takes into account the dilution of clinker by other cement ingredients. Humphreys and Mahasenan [2] report that the cement industry emitted in 2000, on average, 0.87kg of CO2 for every kg of cement produced (worldwide cement production in 2000: 1.57billion tonnes, in 2004: over 2billion tonnes).
>An analysis carried out by Battelle [2] shows that cement sector CO2 emissions are set to rise dramatically in the coming decades. Demand for cement in industrial nations is increasing slowly, but in developing countries it rose by 55% in the 1990s. It is expected that, by 2020, global demand will have increased by 115–180% from 1990 levels, with a four-fold increase likely by 2050. It is critical that the CO2 emissions associated with such growth in cement production be reconciled with international efforts to reduce GHG effects. The cement industry is fully aware of the sustainable development stakes and, over the past decades, has been actively involved in seeking ways to consume less energy and natural resources, and emit less CO2 per unit of cement produced. Recent innovations such as self-compacting concrete, high-performance concrete and surface-active materials further contribute to sustainable development by reducing the costs of construction and maintenance, improving health and safety as well as the outdoor and indoor environment.
Section snippets
Global warming
Climate change has become an issue of global prominence and, in today's society, often provokes animated debates over its origins. Most of the scientific evidence, however, links increased GHG emissions to the average warming of our planet.
How do GHG emissions affect the climate? The Sun's radiation heats the surface of the Earth, which in turn radiates energy back to space. Some of this radiation (almost all in the infrared spectrum) is trapped in the atmosphere by GHGs, which have strong
Alternative fuels and raw materials
A typical modern rotary cement kiln with a specific heat consumption of 3.1GJ/t clinker, burning traditional carbon based fuels such as coal, oil or petroleum coke, emits approximately 0.31kg fuel derived CO2/kg clinker. Given a more realistic world average specific heat consumption of 3.8GJ/t clinker, fuel derived CO2 emissions would amount to approximately 0.37kg/kg clinker. Towards the top end of the scale, inefficient long rotary kilns burning wet raw materials typically operate at a heat
Reduced CO2 emission and energy consumption in clinker production
The CO2 emissions directly resulting from clinker production fall into two main categories: those derived from de-carbonation of the raw materials, which we denote as RM-CO2, and those derived from the fuel burned in the kiln, which we denote as FD-CO2[5]. The CO2 emissions associated with the generation of the electric power used to operate cement plant machinery (most of which is required for grinding operations) vary widely, depending on the nature of the local electric power industry, but
Reduced clinker contents in cement
Given the limitations involved in reducing CO2 emissions from alternative raw materials and fuels, and by improving kiln efficiency, probably the most effective means of achieving significant reductions lies in the replacement of Portland cement clinker by other suitable materials. These replacement materials can be added separately to the concrete allowing a reduction in the content of clinker for the same concrete performance, or used to replace the clinker in composite cements. The latter is
“Green” concrete
The idea behind “green concrete” is to formulate and use concrete formulations which are optimized for the lowest possible environmental impact in all phases of the concrete structure's life cycle, which include:
- Extraction of raw materials
- Production of constituent materials (cement, additives, reinforcement, etc.)
- Production of concrete
- Transport and erection of the structure
- Maintenance
- Demolition and recycling.
A number of principles may be used to reduce the environmental impact of
Closing the CO2 cycle: CO2 uptake by concrete
When considering the environmental performance of materials one needs to consider effects taking place during the entire life cycle of the material. Failing this may lead to erroneous conclusions when selecting materials based on perceived environmental-friendliness. Some of these effects may be fairly obscure.
One such issue seldom considered is the ability of cement-based materials to permanently absorb (“sequester”) CO2 from the atmosphere. This process is termed carbonation and occurs during
Thermal properties of concrete buildings
From a life-cycle perspective, the energy consumption and resulting CO2 emissions from the operation of buildings are much larger than the energy consumed and CO2 emitted during production of the building materials. It has been calculated [31] that the energy consumption needed to produce a typical reinforced concrete office or residential building is 500MJ per m3 space. Over a 50-year lifespan, however, 15,000MJ per m3 space will be used for heating and electricity consumption. In other words,
Concluding remarks
The current examples of self-compacting concrete, ultra-high performance cement-based materials and surface-active materials show how well-directed R&D can bring innovation into the traditionally conservative concrete construction technology. However, further important R&D efforts are necessary to develop concretes with a wider range of attractive properties, such being as self-cleaning, self-repairing, with better insulating properties, and even more resistant to environmental degradation and
References (37)
Industrially interesting approaches to low-CO2 cements
Cem. Concr. Res.
(2004)- et al.
New concepts for natural gas fired power plants which simplify the recovery of carbon dioxide
Energy Convers. Manag.
(1992) - et al.
Industrial trial production of low energy belite cement
Cem. Concr. Compos.
(2003) Performance of belite-sulfoaluminate cements
Cem. Concr. Res.
(2001)- et al.
High-performance cement matrices based on calcium sulfoaluminate-belite compositions
Cem. Concr. Res.
(2001) Modelling the influence of limestone filler on cement hydration using CEMHYD3D
Cem. Concr. Compos.
(2006)- ...
- et al.
Toward a sustainable cement industry. Sub-study 8: climate change
An Independent Study Commissioned to Battelle by World Business Council for Sustainable Development
(March 2002) - Impacts of Europe's changing climate, European Environment Agency Report no....
- Cembureau Internal Document, Consumption of alternative fuels used in kiln —...
Energy use and carbon dioxide emissions in energy-intensive industries in key developing countries
Development and use of sulfo- and ferro-aluminate cements in China
Adv. Cem. Res.
Cement substitutes focus
Market Report by OneStone Intelligence GmbH
Development and application of high density cement based material
Philos. Trans. R. Soc. Lond., A
Durability of ternary blend concrete with silica fume and blast-furnace slag, laboratory and outdoor exposure site studies
Mater. J.
Effect of triisopropanolamine on hydration and strength development of cements with different character
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