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S. Lotfi
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1
End of Life (EOL) concrete fines, that is often 0–4 m, is one of the massive by-products of concrete recycling. Using this fraction into new concrete is detrimental, due to its high water absorption and mixed contaminants. Although the construction sector is to some extent familiar with the utilization of the coarse fraction of crushed concrete, at present there is no high-quality application for crushed concrete fines. Here we present an effective recycling process on lab scale to separate the cementitious powder from the sandy part in the crushed concrete fines and deliver attractive products with the minimum amount of contaminants. For this study, a lab scale Heating-Air classification System (HAS) was designed and constructed. A combination of heat and air classification, resulted in a proper separation of finer fraction (0–0.250 mm), from coarser fractions. Heating of the materials was followed by ball milling to enhance the liberation of the cementitious fraction. Experiments were carried out at different heating temperatures and milling durations. Experimental results show that by heating the materials to 500 °C for 30 s, the required time of ball milling is diminished by a factor of three and the quality of the recycling products satisfies the market demand. In addition, the removal of contaminants is complete at 500 °C. The amount of CaO in the recovered finer fraction from the recycling process is comparable with the amount of CaO in low-quality limestone. By using this fraction in the cement kiln as the replacement of limestone, the release of the chemically bound CO2 could be reduced by a factor of three. This proof of concept constitutes the starting point for the new HAS technology proposed in the Horizon 2020 VEEP project.
Keywords
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End of Life (EOL) concrete fines, that is often 0–4 m, is one of the massive by-products of concrete recycling. Using this fraction into new concrete is detrimental, due to its high water absorption and mixed contaminants. Although the construction sector is to some extent familiar with the utilization of the coarse fraction of crushed concrete, at present there is no high-quality application for crushed concrete fines. Here we present an effective recycling process on lab scale to separate the cementitious powder from the sandy part in the crushed concrete fines and deliver attractive products with the minimum amount of contaminants. For this study, a lab scale Heating-Air classification System (HAS) was designed and constructed. A combination of heat and air classification, resulted in a proper separation of finer fraction (0–0.250 mm), from coarser fractions. Heating of the materials was followed by ball milling to enhance the liberation of the cementitious fraction. Experiments were carried out at different heating temperatures and milling durations. Experimental results show that by heating the materials to 500 °C for 30 s, the required time of ball milling is diminished by a factor of three and the quality of the recycling products satisfies the market demand. In addition, the removal of contaminants is complete at 500 °C. The amount of CaO in the recovered finer fraction from the recycling process is comparable with the amount of CaO in low-quality limestone. By using this fraction in the cement kiln as the replacement of limestone, the release of the chemically bound CO2 could be reduced by a factor of three. This proof of concept constitutes the starting point for the new HAS technology proposed in the Horizon 2020 VEEP project.
Keywords
Enormous amount of Construction and Demolition Waste (CDW) are yearly generated in Europe and the predominant material constituent is concrete. Despite the urgency of creating a sustainable solution for End Of Life (EOL) concrete waste treatment, there has not been a large driving force for recycling it into prime grade materials. The C2CA concrete recycling process aims at a cost effective system approach to recycle EOL concrete to hardened cement and clean aggregates. This recycling process consists of a combination of smart demolition, gentle grinding of the crushed concrete in an autogenous mill, and a novel dry classification technology called Advanced Dry Recovery (ADR) to remove the fines. The main factors in the C2CA process which may influence the properties of Recycled Aggregates (RA) or Recycled Aggregate Concrete (RAC) include the type of Parent Concrete (PC), the intensity of autogenous milling (changing the amount of shear and compression inside of a mill) and the ADR cut-size point (usage of +2 mm or +4 mm RA in the new concrete). This study aims to investigate the influence of implied factors on the quality of the RA and RAC. To conduct the study, first of all, three types of concrete which are mostly demanded in the Dutch market were cast as PC and their fresh and hardened properties were tested. After nearly one year curing, PC samples were recycled independently varying the type of PC and intensity of the autogenous milling. Experimental variables resulted in the production of eight types of RA. The physical, mechanical and durability properties of the produced RA were tested and the effect of the experimental variables on their properties were investigated. According to the results, the type of PC is a prevailing parameter for the final properties of RA, in comparison with the milling intensity. Moreover, it is observed that a variation in the milling intensity mostly influences the properties of RA produced from a lower strength PC. Furthermore, the performance of the RA in the new concrete was studied. Four types of RAC were produced based on the modified recipe of their corresponding PCs. For the modification of the recipes, water absorption and density of RA were taken into account while the amount of applied cement and consistency class was kept similar to the corresponding PC. Experimental results show that the RAC samples compare favourably with PC. Among various autogenous milling intensities, milling at medium shear and compression delivers better properties for RA and RAC. Good performance of RAC with the incorporation of 2–4 mm ADR fines and RA, confirms the possibility of setting ADR cut-size point on 2 mm.
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Enormous amount of Construction and Demolition Waste (CDW) are yearly generated in Europe and the predominant material constituent is concrete. Despite the urgency of creating a sustainable solution for End Of Life (EOL) concrete waste treatment, there has not been a large driving force for recycling it into prime grade materials. The C2CA concrete recycling process aims at a cost effective system approach to recycle EOL concrete to hardened cement and clean aggregates. This recycling process consists of a combination of smart demolition, gentle grinding of the crushed concrete in an autogenous mill, and a novel dry classification technology called Advanced Dry Recovery (ADR) to remove the fines. The main factors in the C2CA process which may influence the properties of Recycled Aggregates (RA) or Recycled Aggregate Concrete (RAC) include the type of Parent Concrete (PC), the intensity of autogenous milling (changing the amount of shear and compression inside of a mill) and the ADR cut-size point (usage of +2 mm or +4 mm RA in the new concrete). This study aims to investigate the influence of implied factors on the quality of the RA and RAC. To conduct the study, first of all, three types of concrete which are mostly demanded in the Dutch market were cast as PC and their fresh and hardened properties were tested. After nearly one year curing, PC samples were recycled independently varying the type of PC and intensity of the autogenous milling. Experimental variables resulted in the production of eight types of RA. The physical, mechanical and durability properties of the produced RA were tested and the effect of the experimental variables on their properties were investigated. According to the results, the type of PC is a prevailing parameter for the final properties of RA, in comparison with the milling intensity. Moreover, it is observed that a variation in the milling intensity mostly influences the properties of RA produced from a lower strength PC. Furthermore, the performance of the RA in the new concrete was studied. Four types of RAC were produced based on the modified recipe of their corresponding PCs. For the modification of the recipes, water absorption and density of RA were taken into account while the amount of applied cement and consistency class was kept similar to the corresponding PC. Experimental results show that the RAC samples compare favourably with PC. Among various autogenous milling intensities, milling at medium shear and compression delivers better properties for RA and RAC. Good performance of RAC with the incorporation of 2–4 mm ADR fines and RA, confirms the possibility of setting ADR cut-size point on 2 mm.
Conference paper
(2017)
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Somi Lotfi, Peter Rem, Francesco Di Maio, Abraham Teklay, Mingming Hu, E van Roekel, H van der Stelt
Production of waste materials, via industrial and human activities, creates big environmental and economic problems but also opportunities to recover valuable resources. EU28 currently generates 461 million tons per year of ever more complex Construction and Demolition Waste (CDW) with average recycling rates of around 46%. There is still a significant loss of potential valuable minerals, metals and organic materials all over Europe. Considering the fact that public and private sectors have become aware of the urgency and importance of CDW recycling, the European Commission has taken initiatives towards sustainable treatment and recycling of CDW funding three tandem projects focusing on the development of an innovative and sustainable concrete recycling process. To that end, this article will firstly present the main achievements and ongoing activities for developing the innovative concrete recycling technology in the course of the EU C2CA, HISER and VEEP projects. In addition some figures related to the cost of each recycling unit process and the selling price of the recycled products are presented.
...
Production of waste materials, via industrial and human activities, creates big environmental and economic problems but also opportunities to recover valuable resources. EU28 currently generates 461 million tons per year of ever more complex Construction and Demolition Waste (CDW) with average recycling rates of around 46%. There is still a significant loss of potential valuable minerals, metals and organic materials all over Europe. Considering the fact that public and private sectors have become aware of the urgency and importance of CDW recycling, the European Commission has taken initiatives towards sustainable treatment and recycling of CDW funding three tandem projects focusing on the development of an innovative and sustainable concrete recycling process. To that end, this article will firstly present the main achievements and ongoing activities for developing the innovative concrete recycling technology in the course of the EU C2CA, HISER and VEEP projects. In addition some figures related to the cost of each recycling unit process and the selling price of the recycled products are presented.
After a decade of intensive research into the recycling of End-of-Life (EOL) concrete into high-grade new concrete, largely supported by funding from the European Commission, it appears that a circular economy for concrete is techno-economically feasible. A collection of advanced technologies, in particular smart demolition for clean mono-flows of EOL concrete, new attrition and classification processes for removing the fine, moist-, lights- and cement-rich fraction from coarser aggregates, sensor sorters for removing larger pieces of wood, plastics and metals from recycle aggregate, green thermal treatment for concentrating and purifying the EOL cement paste and Laser-Induced Breakdown Spectroscopy tools for verifying the quality of input materials for the mortar facilities, have been put into place to make recycled concrete in some technical aspects even superior to concrete made from river gravel. And at competitive costs. Is this enough to make the transition to circular concrete into a success? Not necessarily. The integration of circular concrete into the routine of construction requires new procedures and agreements between stakeholders to avoid risks in producing an extremely cheap but at the same time strongly quality-guaranteed concrete commodity from a new and variable feedstock. It is argued that extremely tight quality checks should be installed in combination with a commitment of the entire chain to gently increase the fraction of recycled materials into new concrete as the EOL concrete flow grows as a consequence of phasing out buildings from the post-war boom.
...
After a decade of intensive research into the recycling of End-of-Life (EOL) concrete into high-grade new concrete, largely supported by funding from the European Commission, it appears that a circular economy for concrete is techno-economically feasible. A collection of advanced technologies, in particular smart demolition for clean mono-flows of EOL concrete, new attrition and classification processes for removing the fine, moist-, lights- and cement-rich fraction from coarser aggregates, sensor sorters for removing larger pieces of wood, plastics and metals from recycle aggregate, green thermal treatment for concentrating and purifying the EOL cement paste and Laser-Induced Breakdown Spectroscopy tools for verifying the quality of input materials for the mortar facilities, have been put into place to make recycled concrete in some technical aspects even superior to concrete made from river gravel. And at competitive costs. Is this enough to make the transition to circular concrete into a success? Not necessarily. The integration of circular concrete into the routine of construction requires new procedures and agreements between stakeholders to avoid risks in producing an extremely cheap but at the same time strongly quality-guaranteed concrete commodity from a new and variable feedstock. It is argued that extremely tight quality checks should be installed in combination with a commitment of the entire chain to gently increase the fraction of recycled materials into new concrete as the EOL concrete flow grows as a consequence of phasing out buildings from the post-war boom.
The C2CA concrete recycling process consists of a combination of smart demolition, gentle grinding of the crushed concrete in an autogenous mill, and a novel dry classification technology called ADR to remove the fines. The` main factors in the C2CA process which influence the properties of Recycled Aggregates or Recycled Aggregate Concrete (RAC) include the type of Parent Concrete (PC), the intensity of autogenous milling and ADR cut-size point. This study aims to investigate the influence of PC and intensity of the autogenous milling on the quality of the produced recycled aggregates. Three types of concrete which are frequently demanded in the Dutch market were cast as PC and their fresh and hardened properties were tested. After near one year curing of PC samples, they were recycled independently while the aforementioned recycling factors were varied. The effects of different recycling variables on the water absorption, density, crushing resistance and durability of produced recycled aggregates were investigated. According to the results, type of the parent concrete is the predominant factor influencing the properties of the recycled aggregates. Milling intensity was found to be effective on improving the properties of recycled aggregates coming from weaker parent concrete. The experimental results suggest that among various milling intensities, milling at medium shear and medium compression improves the overall quality of RA
...
The C2CA concrete recycling process consists of a combination of smart demolition, gentle grinding of the crushed concrete in an autogenous mill, and a novel dry classification technology called ADR to remove the fines. The` main factors in the C2CA process which influence the properties of Recycled Aggregates or Recycled Aggregate Concrete (RAC) include the type of Parent Concrete (PC), the intensity of autogenous milling and ADR cut-size point. This study aims to investigate the influence of PC and intensity of the autogenous milling on the quality of the produced recycled aggregates. Three types of concrete which are frequently demanded in the Dutch market were cast as PC and their fresh and hardened properties were tested. After near one year curing of PC samples, they were recycled independently while the aforementioned recycling factors were varied. The effects of different recycling variables on the water absorption, density, crushing resistance and durability of produced recycled aggregates were investigated. According to the results, type of the parent concrete is the predominant factor influencing the properties of the recycled aggregates. Milling intensity was found to be effective on improving the properties of recycled aggregates coming from weaker parent concrete. The experimental results suggest that among various milling intensities, milling at medium shear and medium compression improves the overall quality of RA
Numerical modelling of the dehydration of waste concrete fines
An attempt to close the recycling loop
The ever-increasing interest on sustainable raw materials has urged the quest for recycled materials that can be used as a partial or total replacement of fine fractions in the production of concrete. This paper demonstrates a modelling study of recycled concrete waste fines and the possibility of turning them into active constituents for the production of concrete. When construction demolition waste (CDW) fines with particle size 0 - 4mm are exposed to a hot environment, different reactions will occur, especially dehydration and phase changes. A one- dimensional (1D) transient model is developed to predict the conversion of the hydrated concrete fines into their dehydrated state, in which the key processes inside the particle and at the boundary layer outside the particle are properly addressed. The model predicts a final composition of the particle that resembles cement clinker, which means a high potential for reuse in manufacturing concrete. Finally, model results for the mass loss during conversion are experimentally validated using thermogravimetric study.
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The ever-increasing interest on sustainable raw materials has urged the quest for recycled materials that can be used as a partial or total replacement of fine fractions in the production of concrete. This paper demonstrates a modelling study of recycled concrete waste fines and the possibility of turning them into active constituents for the production of concrete. When construction demolition waste (CDW) fines with particle size 0 - 4mm are exposed to a hot environment, different reactions will occur, especially dehydration and phase changes. A one- dimensional (1D) transient model is developed to predict the conversion of the hydrated concrete fines into their dehydrated state, in which the key processes inside the particle and at the boundary layer outside the particle are properly addressed. The model predicts a final composition of the particle that resembles cement clinker, which means a high potential for reuse in manufacturing concrete. Finally, model results for the mass loss during conversion are experimentally validated using thermogravimetric study.
n many developing countries, the rapid growth of town and cities has generated a rising levels of waste and illegal dumps have become a serious issue. The booming construction industry in Mongolia has resulted in the production of massive amounts of CDW which is one of the largest waste streams. In Ulaanbaatar (UB) and other cities in Mongolia, the construction waste is dumped illegally. In order to promote the sustainability of the building industry, plenty of regulations focusing on reducing or recycling the CDW have been carried out worldwide. This paper investigates the current CDW management in Mongolia and proposes a quantification of the amount of CDW in UB by using a Material Flow Analysis (MFA). Questionnaire surveys and interviews were conducted with main stakeholders in construction and recycling sector. From the questionnaire results, it is clear that the awareness about the CDW issues in Mongolia is low among the principal stakeholders in the sector, such as Government agencies and construction companies. On the other hand, recycling in Mongolia belongs to an informal sector and the lack of investment constitutes a major problem. In this regards, the technical and non-technical solutions to improve CDW management system are proposed. A stricter control of landfilling for CDW and a creation of a dedicated regulatory framework specific to CDW are needed. To increase the recovery and recycling rates of materials an optimum demolition strategy (for example process, costs, logistics, procedures, timing) is recommended.
...
n many developing countries, the rapid growth of town and cities has generated a rising levels of waste and illegal dumps have become a serious issue. The booming construction industry in Mongolia has resulted in the production of massive amounts of CDW which is one of the largest waste streams. In Ulaanbaatar (UB) and other cities in Mongolia, the construction waste is dumped illegally. In order to promote the sustainability of the building industry, plenty of regulations focusing on reducing or recycling the CDW have been carried out worldwide. This paper investigates the current CDW management in Mongolia and proposes a quantification of the amount of CDW in UB by using a Material Flow Analysis (MFA). Questionnaire surveys and interviews were conducted with main stakeholders in construction and recycling sector. From the questionnaire results, it is clear that the awareness about the CDW issues in Mongolia is low among the principal stakeholders in the sector, such as Government agencies and construction companies. On the other hand, recycling in Mongolia belongs to an informal sector and the lack of investment constitutes a major problem. In this regards, the technical and non-technical solutions to improve CDW management system are proposed. A stricter control of landfilling for CDW and a creation of a dedicated regulatory framework specific to CDW are needed. To increase the recovery and recycling rates of materials an optimum demolition strategy (for example process, costs, logistics, procedures, timing) is recommended.
Conference paper
(2017)
-
Mingming Hu, B. Miranda-Xicotencat, D. Ita-Nagy, Valentina Prado, Jeroen Guinée, E van Roekel, R. Huismans, F. Rens, Somi Lotfi, Francesco Di Maio
Ninety five percent of the construction and demolition waste is recycled in the Netherlands. Most of it is used for low value applications such as road base materials; the use of secondary material in buildings is still less than 3%7. In order to recover waste for higher value applications, enhancing selective demolition and waste management practices is of crucial importance. In this study Life Cycle Assessment and Life Cycle Costing of a demolition project in Almere was carried out to identify the environmental and financial hotspots in the selective demolition and waste management in the Dutch context. Results suggest that (1) the best practice selective demolition and (2) the substitution of virgin concrete aggregate with secondary aggregate processed by Advanced Dry Recovery (ADR) system, will lead to environmental and financial improvements compared to the business as usual practice. On the building level, the advantage is mainly due to connecting the demolition and the re-development projects, which maximizes local reuse of old building components in the new building. The key of success for selective demolition is pre-audit to identify and connect to the market for material reuse. This is a direction that BIM (building information modeling) technology can contribute. With regards to the ADR concrete aggregate manufacturing, it was found that the transport distance for aggregate supply was the largest contributor to the environmental impacts and costs. Therefore it is important to locate ADR facilities next to concrete manufactures and/or provide ADR service on- site.
...
Ninety five percent of the construction and demolition waste is recycled in the Netherlands. Most of it is used for low value applications such as road base materials; the use of secondary material in buildings is still less than 3%7. In order to recover waste for higher value applications, enhancing selective demolition and waste management practices is of crucial importance. In this study Life Cycle Assessment and Life Cycle Costing of a demolition project in Almere was carried out to identify the environmental and financial hotspots in the selective demolition and waste management in the Dutch context. Results suggest that (1) the best practice selective demolition and (2) the substitution of virgin concrete aggregate with secondary aggregate processed by Advanced Dry Recovery (ADR) system, will lead to environmental and financial improvements compared to the business as usual practice. On the building level, the advantage is mainly due to connecting the demolition and the re-development projects, which maximizes local reuse of old building components in the new building. The key of success for selective demolition is pre-audit to identify and connect to the market for material reuse. This is a direction that BIM (building information modeling) technology can contribute. With regards to the ADR concrete aggregate manufacturing, it was found that the transport distance for aggregate supply was the largest contributor to the environmental impacts and costs. Therefore it is important to locate ADR facilities next to concrete manufactures and/or provide ADR service on- site.
One of the massive by-products of concrete to concrete recycling is the crushed concrete fines, that is often 0 - 4mm. Although the construction sector is to some extent familiar with the utilization of the recycled coarse fraction (>4 mm), at present there is no high-quality application for fines due to its moisturized and contaminated nature. Here we present an effective recycling process on lab scale to separate the cementitious powder from the sandy part in the crushed concrete fines and deliver attractive products with the minimum amount of contaminants. For this study, a lab scale Heating-Air classification system was designed and constructed. A combination of heat and air classification, resulted in a proper separation of finer fraction (0 - 0.250 mm), from coarser fractions. Heating of the materials was followed by ball milling to enhance the liberation of the cementitious fraction. Experiments were carried out at different heating temperatures and milling durations. Experimental results show that by heating the materials to 500˚C for 30 seconds, the required time of ball milling is diminished by a factor of three and the quality of the recycling products satisfies well the market demand. In addition, the removal of contaminants is complete at 500˚C. The amount of CaO in the recovered finer fraction from the recycling process is comparable with the amount of CaO in low-quality limestone. By using this fraction in the cement kiln as the replacement of limestone, the release of the chemically bound CO2 could be reduced by a factor of three.
...
One of the massive by-products of concrete to concrete recycling is the crushed concrete fines, that is often 0 - 4mm. Although the construction sector is to some extent familiar with the utilization of the recycled coarse fraction (>4 mm), at present there is no high-quality application for fines due to its moisturized and contaminated nature. Here we present an effective recycling process on lab scale to separate the cementitious powder from the sandy part in the crushed concrete fines and deliver attractive products with the minimum amount of contaminants. For this study, a lab scale Heating-Air classification system was designed and constructed. A combination of heat and air classification, resulted in a proper separation of finer fraction (0 - 0.250 mm), from coarser fractions. Heating of the materials was followed by ball milling to enhance the liberation of the cementitious fraction. Experiments were carried out at different heating temperatures and milling durations. Experimental results show that by heating the materials to 500˚C for 30 seconds, the required time of ball milling is diminished by a factor of three and the quality of the recycling products satisfies well the market demand. In addition, the removal of contaminants is complete at 500˚C. The amount of CaO in the recovered finer fraction from the recycling process is comparable with the amount of CaO in low-quality limestone. By using this fraction in the cement kiln as the replacement of limestone, the release of the chemically bound CO2 could be reduced by a factor of three.