References of "Zhao, Zengfeng"
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See detailChemico-microstructural changes in earthen building materials containing calcium carbide residue and rice husk ash
Nshimiyimana, Philbert ULiege; Messan, Adamah; Zhao, Zengfeng ULiege et al

in Journal of construction and building materials (2019), 2016

Clay earthen materials can essentially be stabilized with calcium carbide residue (CCR) and rice husk ash (RHA) to produce compressed earth block (CEBs) with improved mechanical performances for ... [more ▼]

Clay earthen materials can essentially be stabilized with calcium carbide residue (CCR) and rice husk ash (RHA) to produce compressed earth block (CEBs) with improved mechanical performances for application in building construction. Nevertheless, the curing process in mixtures of these materials needs to be mon- itored in order to assess the maturation of the reaction among these materials and their reactivity. This study investigated the curing process in mix solutions and microstructural changes in the cured mixtures made of kaolinite-rich earthen material, portlandite-rich CCR, and silica (amorphous)-rich RHA. Dry mix- tures were prepared by adding 0–25% CCR and 10–25% CCR:RHA (various ratios) to the earthen material (5 g). The mix solutions were prepared by addition of 100 mL of deionized water to the dry mixtures. Stabilized CEBs were also produced by manually compressing moisturized mixtures in 295 ? 140 ? 95 mm3 mold. The curing process was undertaken between 1 and 90 days at 40 ± 2 °C. Throughout the curing, the chemical changes in mix solutions were monitored by measuring the pH, elec- trical conductivity (EC) and concentration of unconsumed calcium ions [Ca2+]. The microstructural changes in cured mixtures were characterized using X-Ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The EC and [Ca2+] decreased over the curing time mainly due to the consumption of calcium ions through pozzolanic reaction involving the earthen material with CCR and CCR with RHA. The minimum values of EC and [Ca2+] were reached after 45 days of curing in the mix solutions containing the earthen material and CCR alone and 28 days in those containing the earthen material and CCR:RHA. This was related to the end of the reaction and occurrence ofoptimum maturity in the respective mixtures. The XRD analyses revealed the consumption of kaolinite and portlandite from the raw materials and formation of calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH) in the cured mixtures. The SEM micrographs showed the formation of porridge-like products form- ing an interlocking network which densely cemented the matrix of stabilized CEBs. [less ▲]

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See detailMicrowave radiation as a pre-treatment for standard and innovative fragmentation techniques in concrete recycling
Everaert, Maarten; Stein, Raphael; Michaux, Simon et al

in Materials (2019), 12(3),

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See detailMarket analysis of recycled sands and aggregates in North-West Europe: drivers and barriers
Delvoie, Simon ULiege; Zhao, Zengfeng ULiege; Michel, Frédéric ULiege et al

in Conference Series Earth and Environmental Science (2019, February)

Construction and demolition wastes (C&DW) are estimated at one third of total wastes generated in the European Union (EU) and represent the main flux in volume. Inert materials (e.g. concrete, bricks ... [more ▼]

Construction and demolition wastes (C&DW) are estimated at one third of total wastes generated in the European Union (EU) and represent the main flux in volume. Inert materials (e.g. concrete, bricks, tiles and ceramics) constitute the largest fraction of construction and demolition wastes. These wastes can be recovered as secondary raw materials after a recycling process resulting in the production of recycled sands and aggregates. The market for recycled sands and aggregates is however complex and sensitive. It can be affected by many parameters and may be very variable from one region to another, even in the same country. A quantitative analysis of some market variables is carried out in five NW European countries: Belgium, France, Germany, Luxembourg and the Netherlands. For achieving this analysis, attention is paid to the following data/parameters: generation of inert construction and demolition wastes, production of recycled sands and aggregates and production of natural sands and aggregates. Since the market of recycled products is also governed by transportation costs (mainly transported by road), the study has also compiled data on the density of recycling plants for construction and demolition wastes, the density of pits and quarries extracting natural materials, the density of inert landfills and taxes applied for C&DW landfilling. National/regional legislation and requirements are also included in the analysis. Based on the compiled data and objective reasons, the market of recycled sands and aggregates is more developed and more suitable in the Netherlands and in Flanders (North of Belgium) than in the other investigated countries/regions. [less ▲]

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See detailCO2 CAPTURE FOR MINERALIZED MISCANTHUS AGGREGATES
Courard, Luc ULiege; Zhao, Zengfeng ULiege; Michel, Frédéric ULiege et al

in CO2 Storage in Concrete (2019)

At a time when the cement industry is largely responsible for the production of CO2 in the construction sector, it is useful to make this production a reverse phenomenon: that’s CO2 capture. The CO2 ... [more ▼]

At a time when the cement industry is largely responsible for the production of CO2 in the construction sector, it is useful to make this production a reverse phenomenon: that’s CO2 capture. The CO2 absorption process called carbonation, improves specific properties of the concrete during the conversion of carbon dioxide CO2 into calcium carbonate CaCO3. Current environmental concerns motivate the study of carbonation in order to maximize the absorption of carbon dioxide. Experimentation has been performed on bio-based and recycled concrete aggregates. The long term stability as well as the reinforcement of bio-based aggregates – miscanthus - may be obtained by means of a mineralization process of the natural product: a preparation with a lime and/or cement-based material is necessary to reinforce the cohesion of the bio-based product. Specific conditions for CO2 capture have been tested and concrete blocks have been produced with aggregates. Performances of aggregates and concrete blocks before and after carbonation are presented and show increasing performances in specific situations of CO2 capture. [less ▲]

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See detailOptimizing performances of recycled aggregates for improving concrete properties
Courard, Luc ULiege; Tabarelli, Enrico ULiege; Michel, Frédéric ULiege et al

in Proceedings SMSS 2019 (2019)

Construction waste management is a quite important economic and environmental deal for our societies. More than 2 million tons demolition and construction wastes are annually produced only in Wallonia ... [more ▼]

Construction waste management is a quite important economic and environmental deal for our societies. More than 2 million tons demolition and construction wastes are annually produced only in Wallonia, Southern Region of Belgium: recycling has clearly to be promoted and by products to be valorised as secondary raw materials. The influence of the fine recycled concrete aggregates (FRCA) on the mechanical and durability properties of concrete was used for producing concrete. Concretes with different substitution rates (0, 30 and 100%) of natural sand by the FRCA were manufactured. Mechanical properties (compressive strength) and durability properties (capillary absorption, carbonation depth, and freeze/thaw resistance) were investigated. The results show that the compressive strength of concrete decreased as the substitution of FRCA increased. Durability of concrete could be strongly influenced by the high porosity and water absorption of fine recycled concrete aggregates. Brick fillers (BF) have also been studied for producing Self Compacting Mortars (SCM): introduction of 50 and 100% substitution clearly show a reduction of workability properties if particles water absorption is not taken into account. However, mechanical properties at 7 and 28 days didn’t show a clear impact of the substitution of limestone filler by brick filler. [less ▲]

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See detailVALORIZATION OF CONSTRUCTION AND DEMOLITION WASTE, A ROUTE TO CIRCULAR ECONOMY: THE VALDEM PROJECT VALORISATION DES DÉCHETS DE CONSTRUCTION ET DE DÉMOLITION, UNE VOIE VERS L'ÉCONOMIE CIRCULAIRE : LE PROJET VALDEM
Groslambert, Sylvie ULiege; Léonard, Angélique ULiege; Courard, Luc ULiege et al

Conference (2018, November)

From resource prospective, building and construction sector is responsible for more than third of global resource consumption, including 12% of the fresh water use and its generation of solid waste is ... [more ▼]

From resource prospective, building and construction sector is responsible for more than third of global resource consumption, including 12% of the fresh water use and its generation of solid waste is estimated to be 40% of the total waste volume. At European level, construction and demolition waste is the largest waste stream representing one third of all waste produced in EU. Therefore, the resource efficiency and management is crucial in building construction. A very significant part of the Construction and Demolition Waste (CDW) is not recy-cled today. Also a very limited part is used as a recycled content in the construction and building products and materials. This lack is mainly due to heterogeneity and dispersion of waste flows decreasing efficiency and economic viability of recycling. To address this issue, VALDEM project (funded by Interreg FWVL European Fund) aims to overcome bar-riers to increase up-cycling applications. The project focuses its activities in North of France, Flanders and Walloon regions (Belgium), and stands out from usual approaches by its cross-border view of circular economy. VALDEM aims, on one hand, to optimize buildings end of life management by devel-oping new deconstruction, sorting and recycling processes to produce uniform and ac-cessible material flows. On the other hand, the project aims at increasing recycling and generating high quality secondary materials (concrete and other flows) to be used in fu-ture buildings within an up cycling prospective. And finally it aims at validating the solu-tions from technical, scientific, economic and environmental point of view. The Environmental assessment, based on LCA, consists of identifying hotspots and key aspects to prioritize the efforts of different economic actors. As a first step, an LCA meta-analysis is conducted to provide an environmental picture for different potential activities within the scope of the project. As a next step, a comparative LCA is conducted to assess the environmental benefits and impacts of different solutions proposed in the framework of the project in a decision making context, and to limit the impact transfer and to generate the maximum value for all the stakeholders. Finally, results will be trans-ferred to main actors (recycling operators, buildings contractors, product manufactur-ers …) in the three regions in order to consolidate future key aspects to eco-design a building in light of circular economy. In correlation with this projects, we have used the results of another research project, CONREPAD (BEWARE fellowships), in which some VALDEM operators were involved (ULiège – GeMME, Prof. Luc Courard). The theme is the recycling of waste concrete blocks manufactured by the PREFER company (Belgium), and in particular the substitution of natural aggregates (NA) by crushed waste blocks as recycled concrete aggregates (RCA). The CONREPAD study determined that the integration of 30% of RCA did not alter the mechanical properties of the blocks and was therefore conceivable (B_RCA30 blocks). A comparative LCA is to made to evaluate the impact of the recycling process of the block waste, and to assess the influence of their integration in the making of the blocks in substitution of the NA, in comparison with to the "business as usual" process (NA only). The results do not show significant gain in any impact category because of the very low available amount of waste (1%), as the internal production of RCA added in B_RCA30 blocks can only substitute 3% of the global production of Prefer. An alternative scenario, based on the import of external RCA from a nearby CDW sorting site, shows however a potential gain in all categories, especially in the Land use category (up to 11.5%) if the total production of blocks consists of B_RCA30. In conclusion, globally and in a circular economy perspective, the substitution of NA with RCA from internal production waste blocks and external source of CDW, is an interesting development route to improve the environmental impact of the concrete blocks made by Prefer. [less ▲]

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See detailCaractérisation de briques pour l’élaboration de liants hydrauliques
Grellier, Adèle ULiege; Zhao, Zengfeng ULiege; Remond, Sebastien et al

Scientific conference (2018, November)

Le but est de valoriser les fines de briques issues de la déconstruction et de la démolition. Avant de commencer à travailler sur ces fines de briques, un matériau modèle a été élaboré avec des briques ... [more ▼]

Le but est de valoriser les fines de briques issues de la déconstruction et de la démolition. Avant de commencer à travailler sur ces fines de briques, un matériau modèle a été élaboré avec des briques neuves afin de se défaire des aléas physico-chimiques pouvant venir d’autres constituants tels que le béton, le bois, le plastique pouvant être liés au matériau recyclé. Le travail consiste à caractériser un matériau modèle que sont les fines de briques pour étudier une piste de valorisation en se penchant sur les propriétés liantes potentielles des briques et ainsi pouvoir les incorporer dans des mélanges de liants mixtes avec ou sans activation alcaline. La première étape est celle de la caractérisation des propriétés chimiques (minéralogie, composition chimique) ainsi que des propriétés physiques (capacité pouzzolanique, absorption d’eau) des fines de briques désignées comme matériau modèle. Ensuite deux voies de valorisation de ce même matériau sont étudiées : la première consiste en une incorporation des briques dans les ciments sous forme de substitution de la part cimentaire par les fines briques modèles (pas d’utilisation d’activateurs). La seconde est la voie des matériaux alcali-activés, via une substitution par les fines de briques des laitiers de haut fourneau activés par une base alcaline et une solution silicatée. Des premiers mélanges sont testés pour évaluer leurs propriétés mécaniques (étalement, temps de prise, résistance à la compression). Avec une substitution de 30% de la part cimentaire par les fines de briques modèles, le liant obtenu offre une résistance de 45MPa. Pour les liants avec substitution de 30% par les fines de briques modèles dans les laitiers HF et activation alcaline, le matériau permet d’atteindre une résistance de 55MPa. [less ▲]

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See detailState of the art on recycling techniques for the production of recycled sands and aggregates from construction and demolition wastes
Delvoie, Simon ULiege; Zhao, Zengfeng ULiege; Michel, Frédéric ULiege et al

in Nguyen, T.T.; Waldmann, D.; Venditti, S. (Eds.) Circular Concrete - SeRaMCo - Secondary Raw Materials for Concrete Precast Products (2018, November)

Construction and demolition wastes (C&DW) are estimated at one third of total wastes generated in the European Union (EU) and represent the main flux in volume. These wastes can be recycled in suitable ... [more ▼]

Construction and demolition wastes (C&DW) are estimated at one third of total wastes generated in the European Union (EU) and represent the main flux in volume. These wastes can be recycled in suitable recycling facilities which include a series of techniques able to crush and sort materials to finally produce recycled sands and aggregates with required properties. Common sorting techniques consist in ferrous metal sorting, hand-picking sorting and washing or air shifting sorting. Crushing is usually carried out by an impact or a jaw crusher and less frequently by a cone crusher. A combination of different crushers is also common for stationary recycling plants. In order to continuously improve the quality of the produced recycled materials, results obtained from innovative recycling techniques are also increasingly documented in literature. Some of the main innovative techniques related to C&DW recycling purposes are introduced in the study. [less ▲]

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See detailUtilisation des sables et granulats recyclés dans le béton préfabriqué : comparaison des exigences réglementaires et techniques en Europe
Delvoie, Simon ULiege; Zhao, Zengfeng ULiege; Michel, Frédéric ULiege et al

Conference (2018, November)

L’utilisation des sables et granulats recyclés dans le béton préfabriqué est encore peu fréquente sur le plan industriel, et ce malgré les nombreuses recherches menées sur ce sujet. Dans un premier temps ... [more ▼]

L’utilisation des sables et granulats recyclés dans le béton préfabriqué est encore peu fréquente sur le plan industriel, et ce malgré les nombreuses recherches menées sur ce sujet. Dans un premier temps, cette étude fait le point sur les législations et les réglementations prises par les différents pays du nord-ouest de l’Europe (Allemagne, Belgique, France, Luxembourg et Pays-Bas) en vue de favoriser le recyclage et la valorisation des sables et granulats recyclés issus des déchets de construction et de démolition. Ces pays disposent d’un cadre législatif et réglementaire développé leur permettant d’atteindre l’objectif fixé par la Directive européenne 2008/98/CE visant à recycler et valoriser au moins 70% des déchets non dangereux de construction et de démolition en 2020. Le cadre normatif, en lien avec la production de béton préfabriqué et l’utilisation de sables et granulats recyclés, est ensuite analysé. Les principales normes européennes concernées sont : EN 206:2013+A1:2016 (béton), EN 13369:2018 (produits préfabriqués en béton) et EN 12620:2013 (granulats pour béton). Ces normes ont été, selon les cas, complétées ou non par des annexes nationales. Une attention est portée à la comparaison des différentes normes entre les pays du nord-ouest de l’Europe. Cette analyse comparative se penche (i) sur les taux de substitution maximum définis par la norme EN 206:2013+A1:2016 et les annexes nationales, ainsi que (ii) sur les caractéristiques que doivent avoir les granulats recyclés pour pouvoir être incorporés dans le béton. Les normes belge et française semblent plus restrictives vis-à-vis du taux de substitution maximum par rapport aux autres normes étudiées, tandis que les normes belge et luxembourgeoise semblent plus contraignantes concernant les caractéristiques que doivent avoir les granulats recyclés pour pouvoir être utilisés dans le béton. [less ▲]

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See detailGypsum residues in recycled materials: characterization of fine recycled aggregates
Colman, Charlotte ULiege; Zhao, Zengfeng ULiege; Michel, Frédéric ULiege et al

Scientific conference (2018, August 26)

Globally, half of all generated waste is produced by the building sector. The finer fraction of this construction and demolition waste (C&DW) is often polluted with substances harmful for the durability ... [more ▼]

Globally, half of all generated waste is produced by the building sector. The finer fraction of this construction and demolition waste (C&DW) is often polluted with substances harmful for the durability of concrete, which is why their incorporation into a new structure is generally avoided. The most important contamination present in these materials consists of gypsum (CaSO4.2H2O) residues from the construction or demolition site. The presence of sulfates from this gypsum may complicate and accelerate the sulfate attack reaction, which is a deteriorating process that causes the expansive formation of the mineral ettringite. The high volume of this ettringite will cause an expansive stress within the concrete, with degradation and cracking of the structure as a result. Additionally, the leaching of sulfates can give rise to environmental problems. In this project, the fine fraction of C&DW from different industrial sources was investigated, to establish the gypsum contamination of actual recycled materials. Ion chromatography was used to determine the concentration of water soluble sulfates. Results showed a variable sulfate content, depending heavily on the source of the materials. Nevertheless, the total amounts surpassed the acceptable sulfate contents specified in the European standard EN 206. The obtained information about the concentration and size distribution of sulfate contamination in fine recycled materials (FRA) will help the development of a testing protocol for the effects of internal sulfate attack caused by gypsum residues. [less ▲]

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See detailEffects of limestone filler on the behaviour of recycled aggregate concrete
Zhao, Zengfeng ULiege; Courard, Luc ULiege; Michel, Frédéric ULiege et al

Scientific conference (2018, August 26)

According to the concept of sustainable development, sustainable construction is becoming a hot topic. Large amounts of construction and demolition wastes, especially concrete wastes, are generated ... [more ▼]

According to the concept of sustainable development, sustainable construction is becoming a hot topic. Large amounts of construction and demolition wastes, especially concrete wastes, are generated annually. Meanwhile, large quantities of natural aggregates are needed for the construction of roads, buildings or civil engineering infrastructures. Until now, only a small part of concrete wastes is re-used as recycled concrete aggregates (RCA) in the manufacture of mortar and concrete. The issue of recycling construction and demolition wastes in the concrete industry has been widely explored by many researchers. RCA are mainly composed of an intimate mix between natural aggregates and adherent hardened cement paste or mortar. The later possesses a large water demand which makes it harder to recycle into concrete than natural aggregates. Limestone powder, which is a by-product of calcareous aggregate production, if not used, has to be disposed of in the landfills at a considerable cost. In this paper, the effect of limestone filler on the properties of recycled aggregate concrete (RAC) was studied. Recycled aggregates were produced in the laboratory from the crushing of concrete blocks and were then used as aggregates into new concretes. Concretes were manufactured by adding different percentages of limestone filler (0%, 10% and 20% of the mass of cement) and by replacing 30% of natural aggregate with recycled aggregates. Then, fresh properties and mechanical properties of these concretes were investigated. The results showed that the compressive strength of concrete with the addition of 10% limestone was 47.2 MPa after 28 days, which was larger than the reference concrete (43.1 MPa). [less ▲]

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See detailFeasible use of construction and demolition waste in concrete production: SeRaMCo project
Zhao, Zengfeng ULiege; Delvoie, Simon ULiege; Michel, Frédéric ULiege et al

Conference (2018, August 09)

About 850 million tons of construction and demolition waste (C&DW) are produced yearly in European Union. The Waste Framework Directive 2008/98/EC aims to a minimum target of reuse, recycling, and ... [more ▼]

About 850 million tons of construction and demolition waste (C&DW) are produced yearly in European Union. The Waste Framework Directive 2008/98/EC aims to a minimum target of reuse, recycling, and material recovery of non-hazardous C&DW at 70% by weight until 2020. Recycling of C&DW is quite important and has to be promoted. Up to now, most of recycled C&DW has been used as a base and sub-base materials in road construction, while only a small quantity of C&DW is reused in concrete. Interreg North-Western Europe project SeRaMCo (Secondary Raw Materials for Concrete Precast Products) aims to replace primary raw materials with the high-quality materials recycled from C&DW, e.g. concrete, bricks, tiles and ceramics (CBTC), in production of the cement and concrete products for use in North-Western Europe. To attain this goal, the project will: a) analyse and improve sorting of C&DW; b) develop and test new concrete mixes and technologies for the production of concrete precast products (CPPs) made from the recycled CBTC; c) establish a market niche for CPPs, leading to the economic advantages for the producers and generating new jobs in the construction sector. [less ▲]

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See detailUse of uncontaminated marine sediments in mortar and concrete by partial substitution of cement
Zhao, Zengfeng ULiege; Benzerzour, Mahfoud; Abriak, Nor-Edine et al

in Cement and Concrete Composites (2018)

The disposal of dredged marine sediments has become a major economic and environmental issue in the world. In this study, uncontaminated marine sediments dredged in the harbor of Dunkirk (France) were ... [more ▼]

The disposal of dredged marine sediments has become a major economic and environmental issue in the world. In this study, uncontaminated marine sediments dredged in the harbor of Dunkirk (France) were dried and ground and then used in partial substitution of cement in the manufacture of mortars and concretes. A given volume of cement has been replaced by the same volume of sediment for three substitution contents (10%, 20%, 30%) of a Portland cement CEM I 52.5. The flexural and compressive strengths of mortars decreased when the sediment replacement content increased. However, the mechanical properties of the mortar with 20% replacement of cement with sediments were better than those of a mortar made from cement CEM II/A-LL 32.5 containing a proportion of limestone similar to the sediment substitution. The total porosity measured by mercury intrusion porosimetry of different types of mortars showed that the porosity increased as the sediment substitution content increased but the pore size distribution was shifted toward smaller pores. Finally, it was demonstrated that concrete C30/37 could be designed with 20% cement replaced by sediment without the use of admixture. Additionally, this concrete fulfilled the standards with respect to the total chloride content required for unreinforced concrete. As a conclusion, dried and finely ground uncontaminated sediments appeared to be a very interesting constituent for partially substituting up to 20% of cement as its efficiency overpass limestone filler. [less ▲]

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See detailInternal sulfate attack caused by gypsum contamination of recycled aggregates: development of a swelling test protocol
Colman, Charlotte ULiege; Zhao, Zengfeng ULiege; Michel, Frédéric ULiege et al

Conference (2018, July 12)

Sulfate attack is a deteriorating process for concrete, where the formation of expansive minerals such as ettringite causes the swelling of a material. The sulfates necessary for this reaction can come ... [more ▼]

Sulfate attack is a deteriorating process for concrete, where the formation of expansive minerals such as ettringite causes the swelling of a material. The sulfates necessary for this reaction can come from an external (such as sea- or groundwater) or an internal (such as cement or aggregates) source. A specific situation within this problematic is the contamination of recycled aggregates with gypsum from the demolition site. To assess the extent of the damage that this gypsum contamination can cause, the length of cementitious mixes that incorporated recycled aggregates needs to be monitored. The challenge in this research exists in finding the right testing protocol to follow the development of sulfate attack. Being a slow reaction which can take several months, accelerating procedures could be necessary. Different methods are described, but do not seem to be applicable in this specific context of gypsum contamination. In this paper, fine recycled aggregates contaminated with different levels of gypsum are subjected to a set of various storage conditions and/or aging cycles. The results show that existing protocols, set up specifically for internal sulfate attack, do not provide the acceleration or aggravation of the reaction as might have been shown before. A definitive testing protocol, to be used in this specific situation, is eventually proposed. [less ▲]

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See detailWPT1 - Market analysis and formal regulations in NWE
Delvoie, Simon ULiege; Zhao, Zengfeng ULiege; Michel, Frédéric ULiege et al

Report (2018)

In the European Union construction and demolition wastes are estimated at one third of all wastes generated and represent the main flux in volume. Inert materials (e.g. concrete, bricks, tiles and ... [more ▼]

In the European Union construction and demolition wastes are estimated at one third of all wastes generated and represent the main flux in volume. Inert materials (e.g. concrete, bricks, tiles and ceramics) constitute the largest fraction of construction and demolition wastes. However these wastes can be recovered as secondary raw materials after a recycling process resulting in the production of recycled sands and aggregates. An in-depth market analysis of recycled sands and aggregates in NW European countries (Belgium, France, Germany, Luxembourg and the Netherlands) has been performed in the framework of the Interreg NWE project SeRaMCo (Secondary Raw Materials for Concrete precast products). Market of recycled sands and aggregates is complex to understand. It can be affected by many parameters and may be very variable from one region to another, even in the same country. To achieve this analysis, attention has been paid to the following data/parameters: generation of inert construction and demolition wastes, production of recycled sands and aggregates and production of natural sands and aggregates. Since the market of recycled products is also governed by transportation costs (mainly transported by road), the study has also compiled data on the density of recycling plants for construction and demolition wastes, the density of pits and quarries extracting natural materials, the density of inert landfills and taxes applied for CDW landfilling. National/regional legislation and requirements have also been included in the analysis. [less ▲]

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See detailImproving the properties of recycled concrete aggregates by accelerated carbonation
Zhao, Zengfeng ULiege; Remond, Sébastien; Damidot, Denis et al

in Proceedings of the Institution of Civil Engineers. Construction Materials (2018)

Large amounts of construction and demolition wastes, especially concrete wastes, are generated annually. Until now, only a small fraction of concrete wastes has been reused as recycled concrete aggregates ... [more ▼]

Large amounts of construction and demolition wastes, especially concrete wastes, are generated annually. Until now, only a small fraction of concrete wastes has been reused as recycled concrete aggregates (RCA) in the manufacture of mortar and concrete. In order to optimise the use of RCA for new concrete, it is important to improve the properties of RCA. RCA are mainly composed of an intimate mix of natural aggregates and adherent hardened cement paste, which has a much larger porosity than natural aggregates. The influence of accelerated carbonation on the properties of RCA was studied in this work. Original concrete was manufactured and crushed by a jaw crusher in the laboratory. The different fractions of laboratory-produced RCA were stored in an accelerated carbonation room. The mass loss, density, porosity and water absorption of the RCA were tested before and after carbonation. Industrial RCA were also studied for comparison with the laboratory-produced RCA. The results clearly showed that, after accelerated carbonation, the density of the RCA increased due to the transformation of portlandite into calcite. The water absorption and porosity of the RCA decreased after carbonation. [less ▲]

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See detailEffect of saturation state of fine recycled concrete aggregates on the properties of mortars
Zhao, Zengfeng ULiege; Remond, Sébastien; Damidot, Denis et al

in Proceedings of the IV International Conference Progress of Recycling in the Built Environment (2018)

Only a small fraction of concrete wastes is re-used as recycled concrete aggregates (RCA) in the manufacture of mortar and concrete. The fine recycled concrete aggregates (FRCA), essentially composed of ... [more ▼]

Only a small fraction of concrete wastes is re-used as recycled concrete aggregates (RCA) in the manufacture of mortar and concrete. The fine recycled concrete aggregates (FRCA), essentially composed of mortar and hardened cement paste, possesses a large water demand which makes it harder to recycle into concrete and mortar compared to the coarse RCA. In order to optimize the use of FRCA into mortar, the saturation state of FRCA plays an important role on the properties of mortar. In this paper, the influence of saturation state of FRCA (dried or saturated) on the properties of mortars of identical compositions was investigated. The results showed that the slump of mortars containing dried FRCA is always larger than that of mortars containing saturated FRCA. Indeed, in the case of dried FRCA, the theoretical amount of absorbed water is added at the begging of mixing leading to a temporary increase of the initial efficient W/C ratio and volume of paste, leading to a better workability before its absorption in to FRCA. Moreover, the compressive of mortars containing dried FRCA is always larger than that of mortar made with saturated FRCA, which is attributed to a thinner interfacial transition zone (ITZ) improving its mechanical properties. [less ▲]

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See detailInfluence of granular fraction and origin of recycled concrete aggregates on their properties
Zhao, Zengfeng ULiege; Courard, Luc ULiege; Michel, Frédéric ULiege et al

in European Journal of Environmental and Civil Engineering (2018)

Large quantities of construction and demolition wastes are produced each year. In order to make good use of recycled concrete aggregates (RCA) in concrete, it is very important to study the influence of ... [more ▼]

Large quantities of construction and demolition wastes are produced each year. In order to make good use of recycled concrete aggregates (RCA) in concrete, it is very important to study the influence of the granular fraction and the origin of RCA on their properties. In this study, RCA from industrial produced blocks (RCA_Blocks) and slabs (RCA_Slabs) were crushed and then separated into four granular fractions (0/2, 2/6.3, 6.3/14, 14/20 mm). Each granular fraction of RCA was physically characterised. Real RCA from recycling plant were also used for comparison. The results showed that recycled sands offered significantly higher cement paste content (higher bound water content) than coarse recycled aggregates. The fine RCA had therefore a higher water absorption coefficient compared to coarser fractions of RCA. The water absorption of finer fraction of RCA could be extrapolated precisely from the relationship between water absorption and cement paste content (or bound water content) of three coarse fractions of RCA. The values of hardened cement paste content obtained for the RCA_Blocks were lower than those measured on the RCA_Slabs, which was due to a smaller amount of initial cement paste content in blocks. The results showed that RCA_Slabs were more angular than RCA_Blocks. [less ▲]

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