In this study we carry out a detailed environmental evaluation of geopolymer concrete production using the Life Cycle Assessment methodology. The literature shows that the production of most standard ...types of geopolymer concrete has a slightly lower impact on global warming than standard Ordinary Portland Cement (OPC) concrete. Whilst our results confirm this they also show that the production of geopolymer concrete has a higher environmental impact regarding other impact categories than global warming. This is due to the heavy effects of the production of the sodium silicate solution. Geopolymer concrete made from fly ashes or granulated blast furnace slags based require less of the sodium silicate solution in order to be activated. They therefore have a lower environmental impact than geopolymer concrete made from pure metakaolin. However, when the production of fly ashes and granulated blast furnace slags is taken into account during the life cycle assessment (using either an economic or a mass allocation procedure), it appears that geopolymer concrete has a similar impact on global warming than standard concrete. This study highlights that future research and development in the field of geopolymer concrete technology should focus on two potential solutions. First of all the use of industrial waste that is not recyclable within other industries and secondly on the production of geopolymer concrete using a mix of blast furnace slag and activated clays. Furthermore geopolymer concrete production would gain from using waste material with a suitable Si/Al molar ratio in order to minimise the amount of sodium silicate solution used. Finally, by taking into account mix-design technology, which has already been developed for OPC concrete, the amount of binder required to produce a geopolymer concrete could be reduced.
This study evaluates the environmental impact of the cement production and its variations between different cement plants, using Life Cycle Impact Assessment. For that purpose, details of the cement ...production processes are investigated in order to show the respective part of raw materials preparation and clinker production using environmental impacts calculated with CML01 indicators. For the kiln emission data, a European pollutant emission register for French intensive industries is used to quantify the variability of indicators between cement plants. For the CML01 indicators that are controlled by kiln emissions, some of them (i.e. global warming, photochemical oxidation) show variations between cement plants between 20 and 30%, as for other (i.e. acidification, eutrophication, terrestrial ecotoxicity) variations are greater than 40% due to the lack of accurate measurements on both pollutant content and annual flow. Finally, a normalisation, using Western Europe yearly emissions is performed and permits to highlight among all the CML01 indicators which ones are the main impacts for the cement production. Abiotic depletion, global warming, acidification and marine ecotoxicity are the four identified impacts.
Using bamboo-based construction materials has been identified as a potential way of reducing pressure on resources and on the environment. These materials have environmental and mechanical advantages ...over conventional construction materials. In the present research, the life cycle assessment of five bamboo-based construction materials was carried out: bamboo pole, flattened bamboo, woven bamboo mat, glue laminated bamboo and woven bamboo mat panels. The main objective of the present research is to develop a series of life cycle assessment data that can represent the diversity found in the global production of bamboo-based construction materials. This research also aims to present a simplified and cost effective approach to developing this kind of data while maintaining its quality. The results show that the environmental impacts of the studied materials grow with increased industrialization and that electricity mixture and heat energy sources contribute most to the variability of the results. It was found out that the species of bamboo and harvesting practices do not make a significant contribution to the overall environmental impact of bamboo-based construction materials. It was also found out that, in general, the processes contributing most to environmental impact are not always the most significant contributors to the variability of the result. It was possible to establish a relationship between the processes contributing to the variability of the results and the results' uncertainty. In this way, it was demonstrated that it is possible to identify the main processes contributing to the variability of the results and that by improving the quality of this data the overall uncertainty of the results can be reduced. Thus, the proposed approach can be successfully used to assess the environmental impact of non-conventional materials with a high degree of accuracy in a cost-effective way.
•The environmental impact of five bamboo based construction materials was studied.•The goal was to provide reliable data for materials with very diverse production practices.•Analyses of the results' variability and uncertainty were used to validate the data.•The electricity mix and heat source are main contributors to the environmental impact.•The environmental impacts and uncertainty grow with the industrialization of the materials.
The building and construction sector is a major CO
2 producer and climate change perspectives urged to reduce CO
2 emissions. The impact of concrete buildings on environment is mainly due to clinker, ...which is the main material used all over the world to produce cement and which releases a bit less than 1
ton of CO
2 per ton of clinker produced.
In this study, we first evaluate if the medium term CO
2 emission reduction objectives for the cement industry are realistic according to our current scientific and technologic knowledge. We consider two environmental strategies. The first one is the substitution of clinker by mineral additions in cement in order to reduce the environmental cost of the material for a given volume of material; the second one is the reduction of the concrete volume needed for a given construction process by enhancing the concrete performances. The impact on CO
2 emissions of a combination of these options is also roughly evaluated. We show that medium term objectives can be reached although long term objectives will need further research developments. We moreover present here a first step towards mix-design methods associating environmental costs and performance requirements which could allow for a better balance between societal demand in terms of environment and technical building requirements.
Taking advantage of atmospheric carbonation of recycled concrete aggregates (RCA) seems particularly attractive to partially reabsorb the chemical part of CO2 emitted during limestone calcination. ...The purpose of this article is to investigate the carbonation mechanism of a heap of RCA. As a first approximation, the rate of CO2 absorption is studied on model materials made of sieved grains of cement paste made of CEM I. Carbonation penetration is measured by gamma-ray attenuation and by thermogravimetric analysis. A model is proposed and verified thanks to experiments. It is based on a dual-scale approach, associating CO2 diffusion through a granular bed and carbonation of the cementitious matrix. Information is provided concerning the influence of the characteristics of the cementitious phase attached to the original aggregates on the CO2 absorption rate. Moreover a study of the carbonatable amount of hydration products is performed according to the composition of the material and the CO2 concentration.
Abstract
The construction and buildings sector is facing an urgent need to reduce GHG emissions and ensure efficient resource utilization while minimizing waste in order to comply with climate change ...policies and circular economy initiatives. Alkali-activated materials, as an alternative binder to CO
2
-intensive conventional cement, show potential in utilizing waste streams from urban environments in their production technology, thereby reducing CO
2
emissions. This study examines two waste streams generated in Switzerland: incineration ashes from municipal solid waste treatment facilities and mineral wool waste from building stock renovation and demolition activities. Geospatial analysis is combined with LCA methods to assess optimal scenarios for waste recycling, utilizing a multi-objective optimization framework based on mixed integer linear programming. The objectives are to minimize the environmental impacts and costs associated with alternative supply chain networks, thereby identifying optimal locations for waste pre-treatment and concrete manufacturing. The proposed scenarios demonstrate reductions of 56% in global warming potential and 29% in costs when compared to the business-as-usual scenario of conventional cement concrete use and waste landfilling. Results show that recycling of urban waste streams in alternative concrete can reduce GHG emissions of industry and heavy transportation sectors by 0.46 mt. CO
2
eq. by year 2030, equivalent to 23% and 4% of the Swiss carbon budget reduction targets for these sectors.
Waste recycling avoids waste landfilling and all associated releases. It also allows for saving non-renewable resources. However, the new commercial interest for waste can be seen as a shift in their ...status from waste to co-product. This has important consequences for environmental load allocation between the different industrial products (and co-products) in industrial plants. In this paper, the specific case of cement has been studied. Actually, to reduce the environmental impact of cement and concrete, industries have been engaged over the last 10 years to increase the replacement of Portland cement by alternative cementitious materials that are principally industrial waste or by-products. In this study, the environmental impacts of two different Supplementary Cementitious Materials (SCM), blast furnace slag and fly ash, are considered using Life Cycle Assessment methodology through a study of the influence of different allocation procedures on environmental impacts of SCM in concrete. Three allocation procedures are tested. In the first one, which is the current practice, no allocations are done. As for the two others, the environmental burdens of the system are respectively associated with the relative mass and some current economic values of the co-products and products. The results are discussed according to the specificity of the cement substitution products (SCM) and the driving forces that are identified for the use of these co-products. Then, a description investigation of another allocation procedure is proposed based on the fact that it is not the relative economic value that permits to evaluate the environmental burdens but the contrary. This last allocation procedure could be generalised for other waste recycling and be used as a regulation tool between the different industrial branches.
Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) is characterized by a unique combination of extremely low permeability, high strength and deformability. Extensive R&D works and applications ...over the last 10years have demonstrated that cast on site UHPFRC is a fast, efficient and price competitive method for the repair/rehabilitation of existing structures. More recently, an original concept of ECO-UHPFRC with a high dosage of mineral addition, a low clinker content, and a majority of local components has been applied successfully for the rehabilitation of a bridge in Slovenia. The objective of the present study is to evaluate the global warming impact of bridge rehabilitations with different types of UHPFRC and to compare them to more standard solutions, both on the basis of the bridge rehabilitation performed in Slovenia. Life Cycle Assessment (LCA) methodology is used. The analysis shows that rehabilitations with UHPFRC, and even more ECO-UHPFRC, have a lower impact than traditional methods over the life cycle.
In this study, the effects of potential technological improvements in cement industry are compared to global goals of sustainability such as those from the Intergovernmental Panel Group for Climate ...Change. In other words, does the current and standard technological knowledge in the cement and concrete industry make it possible to achieve the “factor 4” concept? This concept aims at reducing the CO
2 emissions in developed countries in 2050 by a factor of four from their 1990 levels, after they have first been reduced by a factor of 2 by 2020. The present study shows that it seems technically possible to design concretes to meet “factor 2” objectives whatever the evolution of cement production, but a technological turnaround is needed to reach factor 4 objectives. This technological shift will require not only changes in concrete raw materials and mix designs, but also new building techniques, using less materials for the same final structure.
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