Final Report Summary - C2CA (Advanced Technologies for the Production of Cement and Clean Aggregates from Construction and Demolition Waste)
Executive Summary:
Construction and demolition waste (CDW) is one of the largest solid waste streams in Europe, accounting for around one third of the controlled waste within EU 28. As a consequence of economic development, there is concern about CDW as a cause of environmental pollution. From the viewpoint of urban mining, this stream is a potential source of secondary raw building materials which can be used to replace primary sand, gravel, clay and limestone. A special point of concern is the very low commercial value per ton of primary raw materials used in the building industry.
In the Netherlands most of CDW is currently used as base for roads construction. However in the near future other applications are needed because of the unbalance between demand and offer of such material. The same development is known from the north west of UK where concrete is currently commercially recycled to concrete at large scale. At European Union level most of the CDW is still being land-filled. The single most important reason for this to happen is the cost of the available processes which place the secondary raw materials obtained from CDW out of the market.
C2CA developed a 100% end-of-life (EoL) concrete separation process that produces both aggregates of quality equivalent to natural (virgin) aggregates suitable for use in new concrete production and a Calcium rich (C-S-H) rich feedstock for low-carbon cement production and other special products eliminating problematic residues. The economics of the process is attractive for the following reasons:
• The low energy demand of the unit operations involved
• The possibility of in-situ processing (no transportation cost)
• The possibility to use largely the same facilities as for the production of primary concrete
• Very small amount of residues to be disposed of
Hence C2CA may contribute to creating a sound material-cycle in which there is a simultaneous pursuit of environmental preservation and economic development in the form of new business opportunities and improved competitiveness of European SMEs and industries.
The demonstration of the economic and ecological viability of this technology have been tested on a case study in which the recycling of old buildings and the building of new one was integrated into a single project. It was demonstrated that an appropriately designed, equipped and performed selective demolition in the Netherlands costs only 15% more than the traditional demolition practice, the cost being nearly compensated by the value of the quality materials recovered from the post-demolition waste via the C2CA smart processing of the recycled concrete.
Because of the positive results obtained, two start-up companies (named Grondstoffen Recycling Hoorn” - RAW Materials Recycling Hoorn and ADR Technologies) have been set up to exploit the project results on the market. Besides the innovative C2CA recycling technologies for the recovery of the EoL concrete fraction, different business models to implement them have been devised. These models should minimize the trade costs along the value chain thanks to no transfer of ownership of waste along the process (thus no fees) and to the long-term trust-based cooperation links.
Possible governmental policies that facilitate an efficient transition towards a combination of optimal value recovery from C&DW and sustainable building should promote green public procurement, by means of minimum recycled material use targets that can be requested in public tenders.
Project Context and Objectives:
The recycling of end-of-life concrete into new concrete is one of the most interesting options for reducing worldwide natural resources use and emissions associated with the building materials sector. The production of the cement used in concrete, for example, is responsible for about 8.6% of worldwide CO2 emissions (Rene Klein, CML, Leiden, 2012). Onsite reuse of clean silica aggregate from old concrete saves natural resources and reduces transport and dust, while the re-use of the calcium-rich cement paste has the potential to cut carbon dioxide emissions in the production of new cement by a factor of two. In order to achieve this goal, a new system approach has been studied in which quality control assessed and maintained high standards of concrete demolition waste from the earliest stage of recycling, and novel breaker/sorting technology concentrated silica and calcium effectively into separate fractions at low cost. Finally, the potential of converting the smaller calcium-rich fraction, which is typically also rich in fine organic residues, into new binding agents by thermal processing and mixed with the aggregate into new mortar has been studied. The project aimed to develop three innovative technologies for recycling end-of-life concrete, integrate them with state-of-the-art demolition and building processes and procedures, and test the new system approach on two Dutch concrete towers involving 70,000 tons of concrete. A special feature of this large case study was a new type of government contract which links the recycling of the towers to the re-use of the recycled materials in new buildings. The results of the project have been used to determine which kinds of strategies and policies are most effective to facilitate an efficient transition towards optimal value recovery from Construction and Demolition Waste and sustainable building.
Project Results:
In order to reach the goals of the project, the scientific and technological objective of C2CA project have been defined in the following way:
1. To identify all important factors and materials constituents related to the economic value and ecological impact of C&DW concrete streams
2. To develop sensing technologies and related data interpretation models to characterize feed and product streams
3. To optimize breaker and separation processes for recycling EOL concrete into fine cement paste and coarse aggregate
4. To create models of the chemical reactions and mass transport that are necessary to develop the thermal technology for the conversion of the fine cement fraction into a new cementitious binder
5. To understand the economy and ecology of C&DW recycling to such an extent that policies can be developed that facilitate an efficient transition towards a combination of optimal value recovery from C&DW and sustainable building.
The objectives have been attained in a progressive strategy: simulations and experiments, laboratory tests & performance assessment, small scale demonstrations, application to a case study in collaboration with industry and development of industrial processes and formulation of policy recommendations.
All planned WPs have been properly implemented and important outcomes have been achieved. Herewith the most valuable ones are mentioned:
(a) Results achieved so far show that a proper dismantling of the building benefit the quality of the EoL concrete so that the recycled aggregates contain less contaminants. However field work carried out using EoL concrete coming from the C2CA case study, suggests that the usage of sensors to assess and remove coarse contaminants (wood, plastics, etc.) from the broken concrete at an early stage (just after the crusher) is a critical part of future recycling technologies. This is an important result because dismantling is not common in most European countries. Moreover the costs of dismantling may prevent extensive application of this practice. On the contrary the application of sensing technology to control and maintain high purity of crushed concrete is technically and economically feasible and makes the process more robust and economically attractive. Results indicate that the hyperspectral, NIR and LIBS sensing technologies can be used for the purpose.
(b) C2CA results indicate that using recycled aggregates it is possible to obtain concrete having values of compressive strength essentially higher than concrete made of virgin aggregates (25%-30%). In particular results show that the +4 mm recycled aggregate compares favorably with natural aggregate in terms of workability and the compressive strength of the new concrete, showing 30% higher strength after 7 days.
This unexpected result is in line with earlier unpublished experiments carried out by two other research groups. Although the science behind these successes is not fully clarified, it is clear that (1) fine materials (- 2 mm) have to be removed from the crushed concrete and (2) fragile cement paste has to be removed from the surface of aggregates. An important part of the C2CA research has been to develop a scientific basis and a characterization of recycled aggregate that correlates well with the observed increase in strength. Such a basis and characterization will create an economic and ecologic argument for using the C2CA or similar technologies. Since the mechanical properties of concrete made of recycled aggregates depend on the amount of cement paste attached to the surface of the aggregates, tests to measure the amount of cement paste on aggregates’ surface and to relate this amount to the mechanical properties of the concrete have been developed. Most of the present tests estimate the amount of cement paste calculating the quantity of water absorbed by the cement paste. C2CA developed a faster and more reliable test which uses acids instead of water. The aim was to use the acid test to predict the relative increase in mechanical properties of the concrete.
It has been shown that among various liberation routes, autogenous (attrition) milling, offers low complexity (mobile) and low-cost technology to remove the fragile mortar from the surface of aggregates. After milling, ADR efficiently separates the moist material into fine and coarse fraction. In the course of the second demonstration case of this technology (industrial trial), recycled aggregate was tested into new concrete (RAC) to evaluate the influence of the recycled aggregate (RA) substitution, w/c ratio and type of cement on the mechanical and durability performance of the RAC. According to the results, using RA as alternative aggregate in concrete might increase the overall porosity of concrete compared to the reference concrete. Besides, applying higher amount of w/c by increasing the effective mixing water induces more porosity to the system that makes the situation more difficult.
As it is observed in the experimental results, the concrete samples with the higher amount of mixing water and lower amount of strength shows in most cases worse mechanical and durability properties than the ones prepared with smaller amount of water. On the other hand, the adverse effect of RA is escalated applying a higher amount of w/c in the system. However, according to some tests concrete results, modifying the concrete mix design, based on lower water to cement ratio and using superplasticizer, results in better mechanical and durability properties in RAC. The mechanical and chemical properties of the cement paste are directly responsible for higher resistance of concrete under exposure to aggressive conditions. Thus, all durability properties can be influenced by the choice of cement and the amount of mixing water in the concrete mixture. Based on the C2CA concrete test program and the current situation in European standards and regulations it is concluded that RA is a suitable alternative to natural coarse aggregates for a significant share of concrete applications including structural applications. Replacing more than 50% if the coarse aggregate with recycled concrete – which corresponds to using more than 500 kg of RA per m3 of new concrete – needs to be done more carefully and applications
should be limited to mild exposure conditions.
(c) The development of mobile ADR equipment is one of the important outcomes achieved during the first 18-months project implementation. In combination with a mobile concrete crusher it allows the on-site treatment of a large amount of materials and a significant reduction in road transport. LCC analysis has shown that the development of mobile ADR technology makes recycling concrete into clean aggregate more profitable than on-site breaking for road base aggregate. Moreover ADR technology has shown to be cheaper than the wet process in producing high-quality aggregates. An industrial test trial in the cement plant of HeidelbergCement/ENCI in Maastricht has been carried out. The use of ADR fines as raw material has been investigated. 600 tons of ADR fine fraction material 0-4 mm, using EoL concrete from the Groningen case study, had been used to produce “Green Clinker”. The produced clinker was ground to a cement of the class CEM I 52.5 R – Green Cement. Characterization of the green cement production output of the industrial trial showed that all requirements according to cement standard tested by EN 196 were fulfilled. A maximum ADR fines utilisation rate of 3.9 % and an average of 2.3 % were reached during the industrial test. The results of the industrial test show that it is possible to use the ADR fines as a replacement for the sand fraction in the raw material mix at the ENCI Maastricht cement plant. As far as Physical-Chemical simulations is concerned, the addition of specific milled demolition waste streams (ADR) in the feed of typical (literature) kilns have been studied further with the addition of ADR fines in the inlet feed. Sensitivity analysis on the composition of the feed mixture using test (emulated) batches that have higher calcium content (>12.1% in the ADR) have also been attempted with the present simulator by FORTH, in view of future ADR batches from respective partners that are expected to be more calcium-enriched than present streams. It was found that the sensitivity of the external kiln temperature to the heat transfer conditions and, especially, to the clinker attachment (coating) on the inner kiln surface, was significant. Despite that, the comprehensive 3D simulator that was developed in this project proved to reproduce the correct kiln behavior including that of the easily measurable external kiln temperature. Moreover the sensitivity of the kiln production on the inlet feed composition is significant. The sensitivity of the process on the heat transfer conditions was also found significant mainly through an investigation of the kiln coating effects.
(d) As far as the liberation of mortar from the stony parts is concerned, the experiments focused on varying the degree of liberation by changing the shear and compression force have been carried out. This research aimed to understand how shear and compression, and the combined effect of them inside of an autogenous mill, influence the cement recovery. In order to simulate forces in an autogenous mill in a controlled way, a new set-up was constructed. A central composite experimental design with the help of the MINITAB 16 software for predicting the results of 13 experimental runs was used. According to the regression analysis, the effect of shear and compression on the cement recovery for both 0-1 mm and 0-0.5 mm fractions was found to be strongly linear (P < 0.001). Comparing the main effect plots, force (compression) is slightly more effective than timing (shear). However, based on the achieved results, it is possible to replace the shear and compression with each other with the purpose of raising the cement recovery. Therefore, high amount of produced low-cost shear in an autogenous mill will eliminate the need for the expensive pure compression in a crusher. Variation in the strength of concrete could be compensated by simple changes in the mill feeding, the residence time and the bed height.
Further activities focusing on the liberation of hardened cement from fine fraction has been carried out. The aim of this investigation is mainly to enrich our understanding of the importance of the heating and milling with respect to hardened cement and sand recovery from the crushed concrete fines and to achieve primary information before going the steps further for designing a proper system for industrial scale recycling of fines. Evidence is presented that the amount of hardened cement and sand recovery from crushed concrete fines is influenced by both heating and milling. Results show that taking the advantage of heating for a short duration, the costly time of milling can be much diminished.
Because of the importance of the liberation and separation process, using software developed at FORTH, simulations of the rheological behaviour of particles pertinent to the ADR composition, connected by cylindrical liquid bridges, have been performed. The distance between particles was adjusted properly to include specific amounts of moisture in the liquid bridge. Initial CFD simulations made without mesh adaptation resulted in a concave liquid bridge that seemed to have the correct contact angels. However there was an internal pressure gradient present, which indicates that the simulation was either not in an equilibrium state, or the parameters of the simulation (e.g. meshing, time steps) are not adequate. This was corrected in subsequent simulations using a level-set method for multiphase CFD calculations using moving meshes (adaptation) for the description of the water-air interface. The simulation also showed a velocity field that was continuous at the boundary, indicating a mass exchange (evaporation) between the liquid and vapor phase.
For the calculation of dynamic conditions, small sphere with specific radii pertinent to the ADR composition were investigated. Liquid bridges were calculated for connections with larger spheres, while 3 levels of constant water volume of the small sphere volume were studied. The contact angle was set accordingly, while the surface tension was set to literature data for water-air interface. Using these data a very good agreement between FORTH and TUDelft methods were noticed.
The mechanisms, the basic phenomena, and the characteristic time and length scales that describe the moist grain separation during the ADR process, were elucidated quantitatively using multiphase CFD simulation performed by FORTH. A very good agreement was found between FORTH and TUDelft methods for steady state experiments. The effect of the volume ratio of the water bridge and the relative ADR grain size on the force acting on the accelerated grains have been investigated quantitatively using transient simulations. Dynamic experiments showed very promising results, revealing the internal processes of the ADR separation. Results can be incorporated into more accurate particle dynamics simulations, however they are very time-consuming to be performed during the course of this project.
(e) A robust LIBS system integrated with a fast camera and a laser triangulation sensor has been tested under envisioned online conditions for beyond monolayer inspection of ADR input products based on a physical sampling model assuming homogeneous particle packing. The particle numbers of different demolition concrete components detected on the stream surface were successfully correlated with those in material stream bulk. Influences of several practical issues such as air, moisture, varying surface roughness of the material flow on the conveyor have been extensively investigated and setup has been optimized for this specific application. A sensitivity study combing two different sampling schemes shows that LIBS can deliver information on both the thickness and homogeneity of a thin calcium rich adhered layer on fine aggregate surface. Furthermore, a traceability study starting form drill core concrete, to final ADR output products after fine-tuning has been conducted based on a standard-less calibration-free LIBS (CF-LIBS) algorithm to extract quantitative element contents. The CF-LIBS results were first used as indicators for the quality of the product, and then correlated with material processing parameters such as heating temperature and milling time. By virtue of our developed software for online processing, the CF-LIBS results can offer feedbacks for material processing effects in real-time.
An HyperSpectral Imaging (HSI) based architecture was preliminary developed and set up first at laboratory and then at real-scale in order to perform two actions, that is:
• off-line characterization of concrete drill cores collected from demolition sites and
• on-line characterization of to evaluate the quality of aggregates particles (i.e. composition) as resulting from specialized comminution-classification actions.
1st action: concrete drill core. Reflectance Spectroscopy (RS) across the visible, near and short infrared spectral region (400-2500 nm) can be utilized to assess the status of the concrete in situ. The fundamental vibrations of most building materials generate spectral information in the mid-infrared region (2500-14000 nm), and overtones and combination modes in the near and shortwave infrared region (900-2500 nm). In addition, the possibility to perform a topological assessment of the different materials constituting a concrete and/or concrete-milled-derived-products is what really need to design innovative recycling strategies in DW sector. Starting from this premises The fulfilment of this goal can be reached adopting an innovative characterization strategy, based on HSI working in shortwave infrared region (SWIR) (1000-2500 nm), able to realize a low-impact-real-time collection of the information concerning dismantled materials. The core samples, drilled from different buildings and collected from different floors and locations (i.e. same room, but one core collected from floor and one from wall), were cut in two halves. In order to perform the HSI analysis, every half drill core was then cut in slices and a side of each slice was analyzed. Mortar and aggregates have been correctly identified and their distribution (in area %) quantitatively assessed. Also the size class distribution of aggregates have been measured starting from the classified image
2nd action: aggregates. The proposed approach, working in the near infrared range (1000-1700 nm), was adopted to develop non-destructive, rapid and low cost analytical strategies finalized to detect the degree of liberation of concrete aggregates from mortar paste. HSI procedures were implemented after particle composition analysis, performed by micro X-ray fluorescence spectrometry (micro-XRF). This analysis was carried out for selecting particles similar in terms of chemical composition, to be utilized both for training and validation stages. Different chemometric techniques were the applied in order to analyze acquired hyperspectral images and to characterize particles aggregates attributes. The built model produces a good classification even if some sporadic misclassifications occur. In any case, it allows to identify which particles are aggregates, mortar or a mixture of them. Some errors in prediction seem to be linked to boundary effects or to the surface heterogeneity of these materials. The “intrinsic” 3D structure of particles, together with their morphological and morphometric attributes, contributes to generate light scattering problem, influencing classification.
For both the actions a preliminary reduction of investigated wavelengths was carried out in order to eliminate background noise. Pre-processing algorithms were then applied in order to highlight sample spectra differences and to remove the influence of possible external sources of variability. Different combinations of Detrend (1st polynomial), Mean-Centering (MC), 1st Derivative, Standard Normal Variate (SNV), Generalized Least Squares Weighting (GLSW) and Baseline techniques were thus utilized. After preprocessing, an exploratory data analysis was carried out. A Principal Component Analysis (PCA). Finally, Partial Least Square-Discriminant Analysis (PLS-DA) was used to build a predictive model, able to classify samples in one or another category.
The proposed HSI based approach is, for both the materials (i.e. concrete drill cores and concrete derived aggregates), objective, fast and non-destructive: it allows performing low-cost analysis. This latter aspect is very relevant especially with reference to the secondary raw materials sector, where expensive and sophisticated control architectures are not adoptable, both for technical (i.e. particles of different size, shape and composition) and economic reasons (i.e. relatively low value of the materials to recover).
(f) The economic analysis shows: (1) C2CA innovation has potential to reduce the net cost for EOL concrete recycling. (2) Most of the additional value addition is realized through the improved mobility of the EOL concrete processing system. (3) Generating cleaner EOL concrete does not necessarily raise the costs of treatment but it will require a change in mind-set. (4) Quality control system is essential to assure the expected market value of the ADR products.
The results of the mass flow analysis show that cost effective recycling is essential for promoting recycling as opposed to down cycling practices in EOL concrete. If widely implemented, the C2CA technology can increase concrete recycling rates in the Netherlands from the current rate of 8% to 40% by 2025. If there are no developments in the recycling technology, the use of secondary aggregates in Dutch concrete manufacturing will remain below 6%.
The strategy to improve concrete recycling is to make recycled concrete a regular, competitive, commercial product. There are three levels of intervention to achieve this: 1) at EU level, it is necessary to standardize evaluation methods and building legislations to facilitate the use of recycled concrete, 2) at the national level, it is important to ban landfilling of EOL concrete and set preconditions for demolition that ensure recycling of concrete, 3) At local level, it is essential to implement demolition practices capable of producing high grade EOL concrete.
(g) Several dissemination activities have been implemented by the project team members. Among them, three very relevant workshops have been attended/organized by C2CA staff members. Moreover a Duurzaam Beton (Ver)bindt" has been organized by Strukton and Heidelberg Cement on February 12, 2014 at Bomencentrum in Baarn (NL). During the seminar, issues of high-quality solutions in construction projects, construction waste, costs reduction and construction safety have been discussed. During the seminar also the latest ideas and technologies developed at TU Delft within the C2CA project, the Green Deal Concrete and recent projects in which Strukton and HeidelbergCement are involved in Benelux countries have been presented by C2CA team members. 69 attendants from companies, governmental organizations and research centers participated to the event.
Eight students have been exchanged between partners universities and companies. While working on their final MSc or PhD project, students focused on diverse topics dealt with within the C2CA project.
A training course for 102 technicians, engineers and management staff members of relevant construction industry has been organized. During the course attendants were introduced with the main information about the new EoL concrete C2CA processes.
A relevant number of publications (46) have been published on journals or conference proceedings. Moreover three PhD theses will be defended within 2015-2016. Because of the interest shown by people involved in the concerned fields, it is believed that C2CA is going to have a big impact at European level. To this extent it is worth to mention that Dutch government and industry are interested to implement the new concept. A company having as shareholders two of the C2CA partners (Strukton and HC) and the name C2CA has been set up to exploit the C2CA technology on the market. Another spin-off company named ADR – Technologies has been set up by TUDelft.
Potential Impact:
The potential impact of the C2CA project is to foster a fundamental change in the use of the concrete component of C&DW: from material that is largely land filled or reused in low-grade applications to resources for high-grade recycle concrete. This object is pursued through the development of breakthrough technologies for the liberation and production of cement and clean aggregates of high and consistent quality from C&DW streams. The development of process control and quality control technologies will contribute to achieve the target.
The demonstration of the economic and ecological viability of this technology have been tested on a case study in which the recycling of old buildings and the building of new one was integrated into a single project. It was demonstrated that an appropriately designed, equipped and performed selective demolition in the Netherlands costs only 15% more than the traditional demolition practice, the cost being nearly compensated by the value of the quality materials recovered from the post-demolition waste via the C2CA smart processing of the recycled concrete.
Because of the positive results obtained, two start-up companies (named Grondstoffen Recycling Hoorn” (RAW Materials Recycling Hoorn) and ADR Technologies) have been set up to exploit the project results on the market.
A new company “C2CA International” is being set up. Within this company, the new concrete recycling techniques (fine fraction solutions) will be fine-tuned. Moreover the new techniques including the ADR will be exploited (first in the Netherlands and secondly internationally wide).
Besides the innovative C2CA recycling technologies for the recovery of the EoL concrete fraction, different business models to implement them have been devised. These models should minimize the trade costs along the value chain thanks to no transfer of ownership of waste along the process (thus no fees) and to the long-term trust-based cooperation links.
Possible governmental policies that facilitate an efficient transition towards a combination of optimal value recovery from C&DW and sustainable building should promote green public procurement, by means of minimum recycled material use targets that can be requested in public tenders.
The C2CA project maximizes its economic and ecological impact through the commitment of large construction and construction materials industries. The impacts are both strategic and direct. The most important strategic goal of the project is the creation of a European-wide sustainable high-value outlet for end-of-life concrete. At this moment, the recycling infrastructure for end-of-life buildings in some European member states has advanced to the point that buildings are being properly dismantled and selectively demolished. The costs of this infrastructure are paid for by the high market value of the clean recycle products. Unfortunately, the present outlet for the largest recycle material fraction (concrete) has been not sustainable so far. By creating a parallel outlet that is sustainable, prices for EoL concrete will remain high, perhaps even increase, so that the advance of proper dismantling and selective demolition continues into all of Europe. C2CA will trigger the market demand for high-volume C&DW by separating the concrete fraction into its components and by using them into high-value applications. An important strategic goal of the project is to demonstrate to the fast growing Far Eastern economies, with their very short cycles of building and demolishing, that vast amounts of CO2 can be saved in the production of building materials. Finally, the C2CA route opens the way to a smooth transfer from primary to secondary raw materials without the risk of quality problems, and it facilitates the logistic optimization of building material transport in Europe, concrete being about half of all building materials transport. There are also direct economic, environmental and social benefits to be gained by the C2CA project. C2CA will promote a more efficient use of resources, and the application of new, greener technologies will stimulate growth, create new jobs and will help the EU to meet its environmental and climate goals.
The economic impact relates to a shift from primary production and waste storage to secondary production and reduced waste storage. Generally, the production of secondary materials creates significantly more jobs than the production of primary materials and this is especially true for the C2CA route, since the high-value market outlet for concrete stimulates also the activities of dismantling and selective demolition.
As far as the wider societal implications is concerned, it is believed that the proper roll out of the C2CA solution on the market, is going to benefit the society at large. In particular in terms of improved environmental conditions and job creation. The rationale of above statement comes from the following considerations:
The technologies to produce high quality aggregates do exist (e.g. thermal process, wet process) for quite some time. However they are expensive and therefore can hardly be implemented on the market. C2CA has developed a cheap and effective process that makes possible to recycle End of Life (EOL) concrete into high-grade aggregate for new concrete production. Considering that a large amount of concrete waste is currently produced in Europe (about 380 Mt), if 70% is going to be recycled, a turnover of about 3.9 billion euro and about 33.000 jobs will be generated (1).
Because of the above considerations, C2CA is going to increase the role that recycling is currently playing in the circular economy.
(1) These calculations assume that 120.000 euro turnover generates one job (cf. EEA Report, No 8/2011, Earning, Jobs and Innovation: The role of Recycling in a Green Economy), and that all clean aggregates have an average value of 15 euro/t (cf. Soutos, M., Fulton, M. C., Recycling of demolition waste in Merseyside, Proceedings of the Institution of Civil Engineers, 2015.
List of Websites:
www.c2ca.eu
Dr. Francesco Di Maio, MBA
Delft University of Technology
Faculty of Civil Engineering and Geosciences
Stevinweg 1, 2628 CN Delft, The Netherlands
+31 15 278 81 48 (office)
+31 15 278 81 62 (fax)
+31 6 186 859 65 (mobile)
Construction and demolition waste (CDW) is one of the largest solid waste streams in Europe, accounting for around one third of the controlled waste within EU 28. As a consequence of economic development, there is concern about CDW as a cause of environmental pollution. From the viewpoint of urban mining, this stream is a potential source of secondary raw building materials which can be used to replace primary sand, gravel, clay and limestone. A special point of concern is the very low commercial value per ton of primary raw materials used in the building industry.
In the Netherlands most of CDW is currently used as base for roads construction. However in the near future other applications are needed because of the unbalance between demand and offer of such material. The same development is known from the north west of UK where concrete is currently commercially recycled to concrete at large scale. At European Union level most of the CDW is still being land-filled. The single most important reason for this to happen is the cost of the available processes which place the secondary raw materials obtained from CDW out of the market.
C2CA developed a 100% end-of-life (EoL) concrete separation process that produces both aggregates of quality equivalent to natural (virgin) aggregates suitable for use in new concrete production and a Calcium rich (C-S-H) rich feedstock for low-carbon cement production and other special products eliminating problematic residues. The economics of the process is attractive for the following reasons:
• The low energy demand of the unit operations involved
• The possibility of in-situ processing (no transportation cost)
• The possibility to use largely the same facilities as for the production of primary concrete
• Very small amount of residues to be disposed of
Hence C2CA may contribute to creating a sound material-cycle in which there is a simultaneous pursuit of environmental preservation and economic development in the form of new business opportunities and improved competitiveness of European SMEs and industries.
The demonstration of the economic and ecological viability of this technology have been tested on a case study in which the recycling of old buildings and the building of new one was integrated into a single project. It was demonstrated that an appropriately designed, equipped and performed selective demolition in the Netherlands costs only 15% more than the traditional demolition practice, the cost being nearly compensated by the value of the quality materials recovered from the post-demolition waste via the C2CA smart processing of the recycled concrete.
Because of the positive results obtained, two start-up companies (named Grondstoffen Recycling Hoorn” - RAW Materials Recycling Hoorn and ADR Technologies) have been set up to exploit the project results on the market. Besides the innovative C2CA recycling technologies for the recovery of the EoL concrete fraction, different business models to implement them have been devised. These models should minimize the trade costs along the value chain thanks to no transfer of ownership of waste along the process (thus no fees) and to the long-term trust-based cooperation links.
Possible governmental policies that facilitate an efficient transition towards a combination of optimal value recovery from C&DW and sustainable building should promote green public procurement, by means of minimum recycled material use targets that can be requested in public tenders.
Project Context and Objectives:
The recycling of end-of-life concrete into new concrete is one of the most interesting options for reducing worldwide natural resources use and emissions associated with the building materials sector. The production of the cement used in concrete, for example, is responsible for about 8.6% of worldwide CO2 emissions (Rene Klein, CML, Leiden, 2012). Onsite reuse of clean silica aggregate from old concrete saves natural resources and reduces transport and dust, while the re-use of the calcium-rich cement paste has the potential to cut carbon dioxide emissions in the production of new cement by a factor of two. In order to achieve this goal, a new system approach has been studied in which quality control assessed and maintained high standards of concrete demolition waste from the earliest stage of recycling, and novel breaker/sorting technology concentrated silica and calcium effectively into separate fractions at low cost. Finally, the potential of converting the smaller calcium-rich fraction, which is typically also rich in fine organic residues, into new binding agents by thermal processing and mixed with the aggregate into new mortar has been studied. The project aimed to develop three innovative technologies for recycling end-of-life concrete, integrate them with state-of-the-art demolition and building processes and procedures, and test the new system approach on two Dutch concrete towers involving 70,000 tons of concrete. A special feature of this large case study was a new type of government contract which links the recycling of the towers to the re-use of the recycled materials in new buildings. The results of the project have been used to determine which kinds of strategies and policies are most effective to facilitate an efficient transition towards optimal value recovery from Construction and Demolition Waste and sustainable building.
Project Results:
In order to reach the goals of the project, the scientific and technological objective of C2CA project have been defined in the following way:
1. To identify all important factors and materials constituents related to the economic value and ecological impact of C&DW concrete streams
2. To develop sensing technologies and related data interpretation models to characterize feed and product streams
3. To optimize breaker and separation processes for recycling EOL concrete into fine cement paste and coarse aggregate
4. To create models of the chemical reactions and mass transport that are necessary to develop the thermal technology for the conversion of the fine cement fraction into a new cementitious binder
5. To understand the economy and ecology of C&DW recycling to such an extent that policies can be developed that facilitate an efficient transition towards a combination of optimal value recovery from C&DW and sustainable building.
The objectives have been attained in a progressive strategy: simulations and experiments, laboratory tests & performance assessment, small scale demonstrations, application to a case study in collaboration with industry and development of industrial processes and formulation of policy recommendations.
All planned WPs have been properly implemented and important outcomes have been achieved. Herewith the most valuable ones are mentioned:
(a) Results achieved so far show that a proper dismantling of the building benefit the quality of the EoL concrete so that the recycled aggregates contain less contaminants. However field work carried out using EoL concrete coming from the C2CA case study, suggests that the usage of sensors to assess and remove coarse contaminants (wood, plastics, etc.) from the broken concrete at an early stage (just after the crusher) is a critical part of future recycling technologies. This is an important result because dismantling is not common in most European countries. Moreover the costs of dismantling may prevent extensive application of this practice. On the contrary the application of sensing technology to control and maintain high purity of crushed concrete is technically and economically feasible and makes the process more robust and economically attractive. Results indicate that the hyperspectral, NIR and LIBS sensing technologies can be used for the purpose.
(b) C2CA results indicate that using recycled aggregates it is possible to obtain concrete having values of compressive strength essentially higher than concrete made of virgin aggregates (25%-30%). In particular results show that the +4 mm recycled aggregate compares favorably with natural aggregate in terms of workability and the compressive strength of the new concrete, showing 30% higher strength after 7 days.
This unexpected result is in line with earlier unpublished experiments carried out by two other research groups. Although the science behind these successes is not fully clarified, it is clear that (1) fine materials (- 2 mm) have to be removed from the crushed concrete and (2) fragile cement paste has to be removed from the surface of aggregates. An important part of the C2CA research has been to develop a scientific basis and a characterization of recycled aggregate that correlates well with the observed increase in strength. Such a basis and characterization will create an economic and ecologic argument for using the C2CA or similar technologies. Since the mechanical properties of concrete made of recycled aggregates depend on the amount of cement paste attached to the surface of the aggregates, tests to measure the amount of cement paste on aggregates’ surface and to relate this amount to the mechanical properties of the concrete have been developed. Most of the present tests estimate the amount of cement paste calculating the quantity of water absorbed by the cement paste. C2CA developed a faster and more reliable test which uses acids instead of water. The aim was to use the acid test to predict the relative increase in mechanical properties of the concrete.
It has been shown that among various liberation routes, autogenous (attrition) milling, offers low complexity (mobile) and low-cost technology to remove the fragile mortar from the surface of aggregates. After milling, ADR efficiently separates the moist material into fine and coarse fraction. In the course of the second demonstration case of this technology (industrial trial), recycled aggregate was tested into new concrete (RAC) to evaluate the influence of the recycled aggregate (RA) substitution, w/c ratio and type of cement on the mechanical and durability performance of the RAC. According to the results, using RA as alternative aggregate in concrete might increase the overall porosity of concrete compared to the reference concrete. Besides, applying higher amount of w/c by increasing the effective mixing water induces more porosity to the system that makes the situation more difficult.
As it is observed in the experimental results, the concrete samples with the higher amount of mixing water and lower amount of strength shows in most cases worse mechanical and durability properties than the ones prepared with smaller amount of water. On the other hand, the adverse effect of RA is escalated applying a higher amount of w/c in the system. However, according to some tests concrete results, modifying the concrete mix design, based on lower water to cement ratio and using superplasticizer, results in better mechanical and durability properties in RAC. The mechanical and chemical properties of the cement paste are directly responsible for higher resistance of concrete under exposure to aggressive conditions. Thus, all durability properties can be influenced by the choice of cement and the amount of mixing water in the concrete mixture. Based on the C2CA concrete test program and the current situation in European standards and regulations it is concluded that RA is a suitable alternative to natural coarse aggregates for a significant share of concrete applications including structural applications. Replacing more than 50% if the coarse aggregate with recycled concrete – which corresponds to using more than 500 kg of RA per m3 of new concrete – needs to be done more carefully and applications
should be limited to mild exposure conditions.
(c) The development of mobile ADR equipment is one of the important outcomes achieved during the first 18-months project implementation. In combination with a mobile concrete crusher it allows the on-site treatment of a large amount of materials and a significant reduction in road transport. LCC analysis has shown that the development of mobile ADR technology makes recycling concrete into clean aggregate more profitable than on-site breaking for road base aggregate. Moreover ADR technology has shown to be cheaper than the wet process in producing high-quality aggregates. An industrial test trial in the cement plant of HeidelbergCement/ENCI in Maastricht has been carried out. The use of ADR fines as raw material has been investigated. 600 tons of ADR fine fraction material 0-4 mm, using EoL concrete from the Groningen case study, had been used to produce “Green Clinker”. The produced clinker was ground to a cement of the class CEM I 52.5 R – Green Cement. Characterization of the green cement production output of the industrial trial showed that all requirements according to cement standard tested by EN 196 were fulfilled. A maximum ADR fines utilisation rate of 3.9 % and an average of 2.3 % were reached during the industrial test. The results of the industrial test show that it is possible to use the ADR fines as a replacement for the sand fraction in the raw material mix at the ENCI Maastricht cement plant. As far as Physical-Chemical simulations is concerned, the addition of specific milled demolition waste streams (ADR) in the feed of typical (literature) kilns have been studied further with the addition of ADR fines in the inlet feed. Sensitivity analysis on the composition of the feed mixture using test (emulated) batches that have higher calcium content (>12.1% in the ADR) have also been attempted with the present simulator by FORTH, in view of future ADR batches from respective partners that are expected to be more calcium-enriched than present streams. It was found that the sensitivity of the external kiln temperature to the heat transfer conditions and, especially, to the clinker attachment (coating) on the inner kiln surface, was significant. Despite that, the comprehensive 3D simulator that was developed in this project proved to reproduce the correct kiln behavior including that of the easily measurable external kiln temperature. Moreover the sensitivity of the kiln production on the inlet feed composition is significant. The sensitivity of the process on the heat transfer conditions was also found significant mainly through an investigation of the kiln coating effects.
(d) As far as the liberation of mortar from the stony parts is concerned, the experiments focused on varying the degree of liberation by changing the shear and compression force have been carried out. This research aimed to understand how shear and compression, and the combined effect of them inside of an autogenous mill, influence the cement recovery. In order to simulate forces in an autogenous mill in a controlled way, a new set-up was constructed. A central composite experimental design with the help of the MINITAB 16 software for predicting the results of 13 experimental runs was used. According to the regression analysis, the effect of shear and compression on the cement recovery for both 0-1 mm and 0-0.5 mm fractions was found to be strongly linear (P < 0.001). Comparing the main effect plots, force (compression) is slightly more effective than timing (shear). However, based on the achieved results, it is possible to replace the shear and compression with each other with the purpose of raising the cement recovery. Therefore, high amount of produced low-cost shear in an autogenous mill will eliminate the need for the expensive pure compression in a crusher. Variation in the strength of concrete could be compensated by simple changes in the mill feeding, the residence time and the bed height.
Further activities focusing on the liberation of hardened cement from fine fraction has been carried out. The aim of this investigation is mainly to enrich our understanding of the importance of the heating and milling with respect to hardened cement and sand recovery from the crushed concrete fines and to achieve primary information before going the steps further for designing a proper system for industrial scale recycling of fines. Evidence is presented that the amount of hardened cement and sand recovery from crushed concrete fines is influenced by both heating and milling. Results show that taking the advantage of heating for a short duration, the costly time of milling can be much diminished.
Because of the importance of the liberation and separation process, using software developed at FORTH, simulations of the rheological behaviour of particles pertinent to the ADR composition, connected by cylindrical liquid bridges, have been performed. The distance between particles was adjusted properly to include specific amounts of moisture in the liquid bridge. Initial CFD simulations made without mesh adaptation resulted in a concave liquid bridge that seemed to have the correct contact angels. However there was an internal pressure gradient present, which indicates that the simulation was either not in an equilibrium state, or the parameters of the simulation (e.g. meshing, time steps) are not adequate. This was corrected in subsequent simulations using a level-set method for multiphase CFD calculations using moving meshes (adaptation) for the description of the water-air interface. The simulation also showed a velocity field that was continuous at the boundary, indicating a mass exchange (evaporation) between the liquid and vapor phase.
For the calculation of dynamic conditions, small sphere with specific radii pertinent to the ADR composition were investigated. Liquid bridges were calculated for connections with larger spheres, while 3 levels of constant water volume of the small sphere volume were studied. The contact angle was set accordingly, while the surface tension was set to literature data for water-air interface. Using these data a very good agreement between FORTH and TUDelft methods were noticed.
The mechanisms, the basic phenomena, and the characteristic time and length scales that describe the moist grain separation during the ADR process, were elucidated quantitatively using multiphase CFD simulation performed by FORTH. A very good agreement was found between FORTH and TUDelft methods for steady state experiments. The effect of the volume ratio of the water bridge and the relative ADR grain size on the force acting on the accelerated grains have been investigated quantitatively using transient simulations. Dynamic experiments showed very promising results, revealing the internal processes of the ADR separation. Results can be incorporated into more accurate particle dynamics simulations, however they are very time-consuming to be performed during the course of this project.
(e) A robust LIBS system integrated with a fast camera and a laser triangulation sensor has been tested under envisioned online conditions for beyond monolayer inspection of ADR input products based on a physical sampling model assuming homogeneous particle packing. The particle numbers of different demolition concrete components detected on the stream surface were successfully correlated with those in material stream bulk. Influences of several practical issues such as air, moisture, varying surface roughness of the material flow on the conveyor have been extensively investigated and setup has been optimized for this specific application. A sensitivity study combing two different sampling schemes shows that LIBS can deliver information on both the thickness and homogeneity of a thin calcium rich adhered layer on fine aggregate surface. Furthermore, a traceability study starting form drill core concrete, to final ADR output products after fine-tuning has been conducted based on a standard-less calibration-free LIBS (CF-LIBS) algorithm to extract quantitative element contents. The CF-LIBS results were first used as indicators for the quality of the product, and then correlated with material processing parameters such as heating temperature and milling time. By virtue of our developed software for online processing, the CF-LIBS results can offer feedbacks for material processing effects in real-time.
An HyperSpectral Imaging (HSI) based architecture was preliminary developed and set up first at laboratory and then at real-scale in order to perform two actions, that is:
• off-line characterization of concrete drill cores collected from demolition sites and
• on-line characterization of to evaluate the quality of aggregates particles (i.e. composition) as resulting from specialized comminution-classification actions.
1st action: concrete drill core. Reflectance Spectroscopy (RS) across the visible, near and short infrared spectral region (400-2500 nm) can be utilized to assess the status of the concrete in situ. The fundamental vibrations of most building materials generate spectral information in the mid-infrared region (2500-14000 nm), and overtones and combination modes in the near and shortwave infrared region (900-2500 nm). In addition, the possibility to perform a topological assessment of the different materials constituting a concrete and/or concrete-milled-derived-products is what really need to design innovative recycling strategies in DW sector. Starting from this premises The fulfilment of this goal can be reached adopting an innovative characterization strategy, based on HSI working in shortwave infrared region (SWIR) (1000-2500 nm), able to realize a low-impact-real-time collection of the information concerning dismantled materials. The core samples, drilled from different buildings and collected from different floors and locations (i.e. same room, but one core collected from floor and one from wall), were cut in two halves. In order to perform the HSI analysis, every half drill core was then cut in slices and a side of each slice was analyzed. Mortar and aggregates have been correctly identified and their distribution (in area %) quantitatively assessed. Also the size class distribution of aggregates have been measured starting from the classified image
2nd action: aggregates. The proposed approach, working in the near infrared range (1000-1700 nm), was adopted to develop non-destructive, rapid and low cost analytical strategies finalized to detect the degree of liberation of concrete aggregates from mortar paste. HSI procedures were implemented after particle composition analysis, performed by micro X-ray fluorescence spectrometry (micro-XRF). This analysis was carried out for selecting particles similar in terms of chemical composition, to be utilized both for training and validation stages. Different chemometric techniques were the applied in order to analyze acquired hyperspectral images and to characterize particles aggregates attributes. The built model produces a good classification even if some sporadic misclassifications occur. In any case, it allows to identify which particles are aggregates, mortar or a mixture of them. Some errors in prediction seem to be linked to boundary effects or to the surface heterogeneity of these materials. The “intrinsic” 3D structure of particles, together with their morphological and morphometric attributes, contributes to generate light scattering problem, influencing classification.
For both the actions a preliminary reduction of investigated wavelengths was carried out in order to eliminate background noise. Pre-processing algorithms were then applied in order to highlight sample spectra differences and to remove the influence of possible external sources of variability. Different combinations of Detrend (1st polynomial), Mean-Centering (MC), 1st Derivative, Standard Normal Variate (SNV), Generalized Least Squares Weighting (GLSW) and Baseline techniques were thus utilized. After preprocessing, an exploratory data analysis was carried out. A Principal Component Analysis (PCA). Finally, Partial Least Square-Discriminant Analysis (PLS-DA) was used to build a predictive model, able to classify samples in one or another category.
The proposed HSI based approach is, for both the materials (i.e. concrete drill cores and concrete derived aggregates), objective, fast and non-destructive: it allows performing low-cost analysis. This latter aspect is very relevant especially with reference to the secondary raw materials sector, where expensive and sophisticated control architectures are not adoptable, both for technical (i.e. particles of different size, shape and composition) and economic reasons (i.e. relatively low value of the materials to recover).
(f) The economic analysis shows: (1) C2CA innovation has potential to reduce the net cost for EOL concrete recycling. (2) Most of the additional value addition is realized through the improved mobility of the EOL concrete processing system. (3) Generating cleaner EOL concrete does not necessarily raise the costs of treatment but it will require a change in mind-set. (4) Quality control system is essential to assure the expected market value of the ADR products.
The results of the mass flow analysis show that cost effective recycling is essential for promoting recycling as opposed to down cycling practices in EOL concrete. If widely implemented, the C2CA technology can increase concrete recycling rates in the Netherlands from the current rate of 8% to 40% by 2025. If there are no developments in the recycling technology, the use of secondary aggregates in Dutch concrete manufacturing will remain below 6%.
The strategy to improve concrete recycling is to make recycled concrete a regular, competitive, commercial product. There are three levels of intervention to achieve this: 1) at EU level, it is necessary to standardize evaluation methods and building legislations to facilitate the use of recycled concrete, 2) at the national level, it is important to ban landfilling of EOL concrete and set preconditions for demolition that ensure recycling of concrete, 3) At local level, it is essential to implement demolition practices capable of producing high grade EOL concrete.
(g) Several dissemination activities have been implemented by the project team members. Among them, three very relevant workshops have been attended/organized by C2CA staff members. Moreover a Duurzaam Beton (Ver)bindt" has been organized by Strukton and Heidelberg Cement on February 12, 2014 at Bomencentrum in Baarn (NL). During the seminar, issues of high-quality solutions in construction projects, construction waste, costs reduction and construction safety have been discussed. During the seminar also the latest ideas and technologies developed at TU Delft within the C2CA project, the Green Deal Concrete and recent projects in which Strukton and HeidelbergCement are involved in Benelux countries have been presented by C2CA team members. 69 attendants from companies, governmental organizations and research centers participated to the event.
Eight students have been exchanged between partners universities and companies. While working on their final MSc or PhD project, students focused on diverse topics dealt with within the C2CA project.
A training course for 102 technicians, engineers and management staff members of relevant construction industry has been organized. During the course attendants were introduced with the main information about the new EoL concrete C2CA processes.
A relevant number of publications (46) have been published on journals or conference proceedings. Moreover three PhD theses will be defended within 2015-2016. Because of the interest shown by people involved in the concerned fields, it is believed that C2CA is going to have a big impact at European level. To this extent it is worth to mention that Dutch government and industry are interested to implement the new concept. A company having as shareholders two of the C2CA partners (Strukton and HC) and the name C2CA has been set up to exploit the C2CA technology on the market. Another spin-off company named ADR – Technologies has been set up by TUDelft.
Potential Impact:
The potential impact of the C2CA project is to foster a fundamental change in the use of the concrete component of C&DW: from material that is largely land filled or reused in low-grade applications to resources for high-grade recycle concrete. This object is pursued through the development of breakthrough technologies for the liberation and production of cement and clean aggregates of high and consistent quality from C&DW streams. The development of process control and quality control technologies will contribute to achieve the target.
The demonstration of the economic and ecological viability of this technology have been tested on a case study in which the recycling of old buildings and the building of new one was integrated into a single project. It was demonstrated that an appropriately designed, equipped and performed selective demolition in the Netherlands costs only 15% more than the traditional demolition practice, the cost being nearly compensated by the value of the quality materials recovered from the post-demolition waste via the C2CA smart processing of the recycled concrete.
Because of the positive results obtained, two start-up companies (named Grondstoffen Recycling Hoorn” (RAW Materials Recycling Hoorn) and ADR Technologies) have been set up to exploit the project results on the market.
A new company “C2CA International” is being set up. Within this company, the new concrete recycling techniques (fine fraction solutions) will be fine-tuned. Moreover the new techniques including the ADR will be exploited (first in the Netherlands and secondly internationally wide).
Besides the innovative C2CA recycling technologies for the recovery of the EoL concrete fraction, different business models to implement them have been devised. These models should minimize the trade costs along the value chain thanks to no transfer of ownership of waste along the process (thus no fees) and to the long-term trust-based cooperation links.
Possible governmental policies that facilitate an efficient transition towards a combination of optimal value recovery from C&DW and sustainable building should promote green public procurement, by means of minimum recycled material use targets that can be requested in public tenders.
The C2CA project maximizes its economic and ecological impact through the commitment of large construction and construction materials industries. The impacts are both strategic and direct. The most important strategic goal of the project is the creation of a European-wide sustainable high-value outlet for end-of-life concrete. At this moment, the recycling infrastructure for end-of-life buildings in some European member states has advanced to the point that buildings are being properly dismantled and selectively demolished. The costs of this infrastructure are paid for by the high market value of the clean recycle products. Unfortunately, the present outlet for the largest recycle material fraction (concrete) has been not sustainable so far. By creating a parallel outlet that is sustainable, prices for EoL concrete will remain high, perhaps even increase, so that the advance of proper dismantling and selective demolition continues into all of Europe. C2CA will trigger the market demand for high-volume C&DW by separating the concrete fraction into its components and by using them into high-value applications. An important strategic goal of the project is to demonstrate to the fast growing Far Eastern economies, with their very short cycles of building and demolishing, that vast amounts of CO2 can be saved in the production of building materials. Finally, the C2CA route opens the way to a smooth transfer from primary to secondary raw materials without the risk of quality problems, and it facilitates the logistic optimization of building material transport in Europe, concrete being about half of all building materials transport. There are also direct economic, environmental and social benefits to be gained by the C2CA project. C2CA will promote a more efficient use of resources, and the application of new, greener technologies will stimulate growth, create new jobs and will help the EU to meet its environmental and climate goals.
The economic impact relates to a shift from primary production and waste storage to secondary production and reduced waste storage. Generally, the production of secondary materials creates significantly more jobs than the production of primary materials and this is especially true for the C2CA route, since the high-value market outlet for concrete stimulates also the activities of dismantling and selective demolition.
As far as the wider societal implications is concerned, it is believed that the proper roll out of the C2CA solution on the market, is going to benefit the society at large. In particular in terms of improved environmental conditions and job creation. The rationale of above statement comes from the following considerations:
The technologies to produce high quality aggregates do exist (e.g. thermal process, wet process) for quite some time. However they are expensive and therefore can hardly be implemented on the market. C2CA has developed a cheap and effective process that makes possible to recycle End of Life (EOL) concrete into high-grade aggregate for new concrete production. Considering that a large amount of concrete waste is currently produced in Europe (about 380 Mt), if 70% is going to be recycled, a turnover of about 3.9 billion euro and about 33.000 jobs will be generated (1).
Because of the above considerations, C2CA is going to increase the role that recycling is currently playing in the circular economy.
(1) These calculations assume that 120.000 euro turnover generates one job (cf. EEA Report, No 8/2011, Earning, Jobs and Innovation: The role of Recycling in a Green Economy), and that all clean aggregates have an average value of 15 euro/t (cf. Soutos, M., Fulton, M. C., Recycling of demolition waste in Merseyside, Proceedings of the Institution of Civil Engineers, 2015.
List of Websites:
www.c2ca.eu
Dr. Francesco Di Maio, MBA
Delft University of Technology
Faculty of Civil Engineering and Geosciences
Stevinweg 1, 2628 CN Delft, The Netherlands
+31 15 278 81 48 (office)
+31 15 278 81 62 (fax)
+31 6 186 859 65 (mobile)
