Search results for: recycled plastics

Authors: Sallehan Ismail, Mahyuddin Ramli

Abstract:

This paper presents the experiment results of investigating the effects of adding various types and proportions of fibre on mechanical strength and permeability characteristics of recycled aggregate concrete (RAC), which was produced with treated coarse recycled concrete aggregate (RCA). Two types of synthetic fibres (i.e., barchip and polypropylene fibre) with various volume fractions were added to the RAC, which was calculated by the weight of the cement. The hardened RAC properties such as compressive strength, flexural strength, ultrasonic pulse velocity, water absorption and total porosity at the curing ages of 7 and 28 days were evaluated and compared with the properties of the control specimens. Results indicate that the treated coarse RCA enhances the mechanical strength and permeability properties of RAC and adding barchip fibre further optimises the results. Adding 1.2% barchip fibre has the best effect on the mechanical strength performance of the RAC.

Keywords: Barchip fibre, polypropylene fibre, recycled aggregate concrete.

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Authors: Michael Tupý, Vít Petránek

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The paper is focused on testing of the poly(vinyl butyral) (PVB) layer which had the function of a CO₂ insulating protection against concrete and mortar carbonation. The barrier efficiency of PVB was verified by the measurement of diffusion characteristics. Two different types of PVB were tested; original extruded PVB sheet and PVB sheet made from PVB dispersion which was obtained from recycled windshields. The work deals with the testing CO₂ diffusion when polymer sheets were exposed to a CO₂ atmosphere (10% v/v CO₂) with 0% RH. The excellent barrier capability against CO₂ permeability of original and also recycled types of PVB layers was observed. This application of PVB waste can bring advantageous use in civil engineering and significant environmental contribution.

Keywords: Windshield, Poly(vinyl butyral), Mortar, Diffusion, Carbonatation, Polymer waste.

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Authors: O. Eren, L. Zakar

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Recycling steel building components is key to the sustainability of a structure’s end-of-life, as it is the most economical solution. In this paper the effects of usage of recycled steel material in tall buildings aspects are investigated.

Keywords: Building, recycled material, steel, structure.

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Authors: M.C.S. Ribeiro, J.P. Meixedo, A. Fiúza, M.L. Dinis, Ana C. Meira Castro, F.J.G. Silva, C. Costa, F. Ferreira, M.R. Alvim

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In this study the effect of incorporation of recycled glass-fibre reinforced polymer (GFRP) waste materials, obtained by means of milling processes, on mechanical behaviour of polyester polymer mortars was assessed. For this purpose, different contents of recycled GFRP waste powder and fibres, with distinct size gradings, were incorporated into polyester based mortars as sand aggregates and filler replacements. Flexural and compressive loading capacities were evaluated and found better than unmodified polymer mortars. GFRP modified polyester based mortars also show a less brittle behaviour, with retention of some loading capacity after peak load. Obtained results highlight the high potential of recycled GFRP waste materials as efficient and sustainable reinforcement and admixture for polymer concrete and mortars composites, constituting an emergent waste management solution.

Keywords: GFRP waste, Mechanical behaviour, Polymer mortars, Recyclability.

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Authors: Michael Tupý, Jaroslav Císař, Pavel Mokrejš, Dagmar Měřínská, Alice Tesaříková-Svobodová

Abstract:

It is the worldwide problem that the recycled PVB is not recycled and it is wildly stored in landfills. However, PVB has similar chemical properties such as PVC. Moreover, both of these polymers are plasticized. Therefore, the study of thermal properties of plasticized PVC and the recycled PVB obtained by recycling of windshields is carried out. This work has done in order to find nondegradable processing conditions applicable for both polymers. Tested PVC contained 38% of plasticizer diisononyl phthalate (DINP) and PVB was plasticized with 28% of triethylene glycol, bis(2-ethylhexanoate) (3GO). The thermal and thermo-oxidative decomposition of both vinyl polymers are compared by calorimetric analysis and by tensile strength analysis.

Keywords: Poly(vinyl chloride), Poly(vinyl butyral), Recycling, Reprocessing, Thermal analysis, Decomposition.

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Authors: Michael Tupý, Dagmar Měřínská, Alice Tesaříková-Svobodová, Christian Carrot, Caroline Pillon, Vít Petránek

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The mechanical properties of blends consisting of plasticized poly(vinyl butyral) (PVB) and plasticized poly(vinyl chloride) (PVC) are studied, in order to evaluate the possibility of using recycled PVB waste derived from windshields. PVC was plasticized with 38% of diisononyl phthalate (DINP), while PVB was plasticized with 28% of triethylene glycol, bis(2-ethylhexanoate) (3GO). The optimal process conditions for the PVB/PVC blend in 1:1 ratio were determined. Entropy was used in order to theoretically predict the blends miscibility. The PVB content of each blend composition used was ranging from zero to 100%. Tensile strength and strain were tested. In addition, a comparison between recycled and original PVB, used as constituents of the blend, was performed.

Keywords: Poly(vinyl butyral), poly(vinyl chloride), windshield, polymer waste, mechanical properties.

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Authors: Lara Alam, Laetitia Van-Schoors, Olivier Sicot, Benoit Piezel, Shahram Aivazzadeh

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Over the last decades, worldwide environmental awareness has grown due to the depletion of raw material resources and global warming. This awareness has prompted the development of new products more environmentally friendly. Among these products are biocomposite materials reinforced with natural fibers. The main challenge in developing the use of biocomposites in exterior applications is the lack of knowledge about their durability and the evolution of their mechanical and physicochemical properties in the long term. The aim of this work is to study the photooxidation of unidirectional (UD) composites based on recycled matrix. For this purpose, UD flax fiber composites based on recycled polypropylene were prepared by thermocompression. An accelerated aging test was carried out using a xenon arc WeatherOmeter. The consequences of UV exposure on the chemical composition and morphology of the surface of composites as well as on their tensile mechanical properties have been reported. The results showed that accelerated aging had a significant effect on the surface of these composites while it had little impact on their mechanical properties.

Keywords: Flax fiber, photooxidation, physico-chemical properties, recycled polypropylene, tensile properties.

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Authors: A. A. Alhazza

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The recycling process of Tungsten alloy (Swarf) by oxidation reduction technique have been investigated. The reduced powder was pressed under a pressure 20Kg/cm2 and sintered at 1150°C in dry hydrogen atmosphere. The particle size of the recycled alloy powder was 1-3 μm and the shape was regular at a reduction temperature 800°C. The chemical composition of the recycled alloy is the same as the primary Swarf.

Keywords: Recycling, Swarf, Oxidation, Reduction.

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Authors: Diana Gómez-Cano, J. C. Ochoa-Botero, Roberto Bernal Correa, Yhan Paul Arias

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To obtain high mechanical performance, the fresh conditions of a mortar are decisive. Measuring the absorption of aggregates used in mortar mixes is a fundamental requirement for proper design of the mixes prior to their placement in construction sites. In this sense, absorption is a determining factor in the design of a mix because it conditions the amount of water, which in turn affects the water/cement ratio and the final porosity of the mortar. Thus, this work focuses on the mechanical behavior of recycled mortars manufactured from moisture correction using the Thermogravimetric Balancing Halogen Light (TBHL) technique in comparison with the traditional ASTM C 128 International Standard method. The advantages of using the TBHL technique are favorable in terms of reduced consumption of resources such as materials, energy and time. The results show that in contrast to the ASTM C 128 method, the TBHL alternative technique allows obtaining a higher precision in the absorption values of recycled aggregates, which is reflected not only in a more efficient process in terms of sustainability in the characterization of construction materials, but also in an effect on the mechanical performance of recycled mortars.

Keywords: Alternative raw materials, halogen light, recycled mortar, resources optimization, water absorption.

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Authors: L. Chiriatti, H. Hafid, H. R. Mercado-Mendoza, K. L. Apedo, C. Fond, F. Feugeas

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Substituting natural aggregate with recycled aggregate coming from concrete demolition represents a promising alternative to face the issues of both the depletion of natural resources and the congestion of waste storage facilities. However, the crushing process of concrete demolition waste, currently in use to produce recycled concrete aggregate, does not allow the complete separation of natural aggregate from a variable amount of adhered mortar. Given the physicochemical characteristics of the latter, the introduction of recycled concrete aggregate into a concrete mix modifies, to a certain extent, both fresh and hardened concrete properties. As a consequence, the behavior of recycled reinforced concrete members could likely be influenced by the specificities of recycled concrete aggregates. Beyond the mechanical properties of concrete, and as a result of the composite character of reinforced concrete, the bond characteristics at the rebar/concrete interface have to be taken into account in an attempt to describe accurately the mechanical response of recycled reinforced concrete members. Hence, a comparative experimental campaign, including 16 pull-out tests, was carried out. Four concrete mixes with different recycled concrete aggregate content were tested. The main mechanical properties (compressive strength, tensile strength, Young’s modulus) of each concrete mix were measured through standard procedures. A single 14-mm-diameter ribbed rebar, representative of the diameters commonly used in the domain of civil engineering, was embedded into a 200-mm-side concrete cube. The resulting concrete cover is intended to ensure a pull-out type failure (i.e. exceedance of the rebar/concrete interface shear strength). A pull-out test carried out on the 100% recycled concrete specimen was enriched with exploratory acoustic emission measurements. Acoustic event location was performed by means of eight piezoelectric transducers distributed over the whole surface of the specimen. The resulting map was compared to existing data related to natural aggregate concrete. Damage distribution around the reinforcement and main features of the characteristic bond stress/free-end slip curve appeared to be similar to previous results obtained through comparable studies carried out on natural aggregate concrete. This seems to show that the usual bond mechanism sequence (‘chemical adhesion’, mechanical interlocking and friction) remains unchanged despite the addition of recycled concrete aggregate. However, the results also suggest that bond efficiency seems somewhat improved through the use of recycled concrete aggregate. This observation appears to be counter-intuitive with regard to the diminution of the main concrete mechanical properties with the recycled concrete aggregate content. As a consequence, the impact of recycled concrete aggregate content on bond characteristics seemingly represents an important factor which should be taken into account and likely to be further explored in order to determine flexural parameters such as deflection or crack distribution.

Keywords: Acoustic emission monitoring, high-bond steel rebar, pull-out test, recycled aggregate concrete.

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Authors: Sallehan Ismail, Mahyuddin Ramli

Abstract:

This paper reports on the influence of surface-treated coarse recycled concrete aggregate (RCA) on developing the compressive strength of concrete. The coarse RCA was initially treated by separately impregnating it in calcium metasilicate (CM) or wollastonite and nanosilica (NS) prepared at various concentrations. The effects of both treatment materials on concrete properties (e.g., slump, density and compressive strength) were evaluated. Scanning electron microscopy (SEM) analysis was performed to examine the microstructure of the resulting concrete. Results show that the effective use of treated coarse RCA significantly enhances the compressive strength of concrete. This result is supported by the SEM analysis, which indicates the formation of a dense interface between the treated coarse RCA and the cement matrix. Coarse RCA impregnated in CM solution results in better concrete strength than NS, and the optimum concentration of CM solution recommended for treated coarse RCA is 10%.

Keywords: Calcium metasilicate, compressive strength, nanosilica, recycled concrete aggregate.

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Authors: Vladimira Vytlacilova

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The article presents findings from the study and analysis of the results of an experimental programme focused on the production of concrete and fibre reinforced concrete in which natural aggregate has been substituted with brick or concrete recyclate. The research results are analyzed to monitor the effect of mechanicalphysical characteristics on the durability properties of tested cementitious composites. The key parts of the fibre reinforced concrete mix are the basic components: aggregates – recyclate, cement, fly ash, water and fibres. Their specific ratios and the properties of individual components principally affect the resulting behaviour of fresh fibre reinforced concrete and the characteristics of the final product. The article builds on the sources dealing with the use of recycled aggregates from construction and demolition waste in the production of fibre reinforced concrete. The implemented procedure of testing the composite contributes to the building sustainability in environmental engineering.

Keywords: Recycled aggregate, Polypropylene fibres, Fibre Reinforced Concrete, Fly ash.

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Authors: Ivanova B. Natalia, Djambova Т. Svetlana, Hristev S. Ivailo

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The acoustic properties of recycled felt panels have been investigated using various methods. Experimentally, the sound insulation of the panels has been evaluated for frequencies in the range of 600 Hz to 4000 Hz, utilizing a small-sized acoustic chamber. Additionally, the sound absorption coefficient for the frequency range of 63 Hz to 4000 Hz was measured according to the EN ISO 354 standard in a laboratory reverberation room. This research was deemed necessary after conducting reverberation time measurements of a university classroom following the EN ISO 3382-2 standard. The measurements indicated values of 2.86 s at 500 Hz, 3.23 s at 1000 Hz, and 2.53 s at 2000 Hz, which significantly exceeded the requirements set by the national regulatory framework (0.6 s) for such premises. For this reason, recycled felt panels have been investigated in the laboratory, showing very good acoustic properties at high frequencies. To enhance performance in the low frequencies, the influence of the distance of the panel spacing was examined. Furthermore, the sound insulation of the panels was studied to expand the possibilities of their application, both for the acoustic treatment of educational and multifunctional halls and for sound insulation purposes (e.g., a suspended ceiling with an air gap passing from room to room). As a conclusion, a theoretical acoustic design of the classroom has been carried out with suggestions for improvements to achieve the necessary acoustic and aesthetic parameters for such rooms.

Keywords: Acoustic panels, recycled felt, sound absorption, sound insulation, classroom acoustics.

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Authors: Vladimira Vytlacilova

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Recycling of construction and demolition waste (C&DW) and their new reuse in structures is one of the solutions of environmental problems. Construction and demolition waste creates a major portion of total solid waste production in the world and most of it is used in landfills all the time. The paper deals with the situation of the recycling of the building and demolition waste in the Czech Republic during the recent years. The paper is dealing with questions of C&D waste recycling, it also characterizes construction and demolition waste in general, furthermore it analyses production of construction waste and subsequent production of recycled materials.

Keywords: Recycling, Construction and demolition waste, Recycled rubble, Waste management.

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Authors: Aleš Florian, Lenka Ševelová

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Low volume roads are widely used all over the world. To improve their quality the computer simulation of their behavior is proposed. The FEM model enables to determine stress and displacement conditions in the pavement and/or also in the particular material layers. Different variants of pavement layers, material used, humidity as well as loading conditions can be studied. Among others, the input information about material properties of individual layers made from recycled materials is crucial for obtaining results as exact as possible. For this purpose the cyclic-load triaxial test machine testing of cyclic-load performance of materials is a promising test method. The test is able to simulate the real traffic loading on particular materials taking into account the changes in the horizontal stress conditions produced in particular layers by crossings of vehicles. Also the test specimen can be prepared with different amount of water. Thus modulus of elasticity (Young modulus) of different materials including recycled ones can be measured under the different conditions of horizontal and vertical stresses as well as under the different humidity conditions. Using the proposed testing procedure the modulus of elasticity of recycled materials used in the newly built low volume road is obtained under different stress and humidity conditions set to standard, dry and fully saturated level. Obtained values of modulus of elasticity are used in FEA.

Keywords: FEA, FEM, geotechnical materials, low volume roads, pavement, triaxial test, Young modulus.

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Authors: Yukinori Taniguchi, Kazuyoshi Kurita, Kohei Mizuta, Keigo Nishitani, Ryuichi Fukuda

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Tungsten carbide is widely used as a tool material in metal manufacturing process. Since tungsten is typical rare metal, establishment of recycle process of tungsten carbide tools and restore into cemented carbide material bring great impact to metal manufacturing industry. Recently, recycle process of tungsten carbide has been developed and established gradually. However, the demands for quality of cemented carbide tool are quite severe because hardness, toughness, anti-wear ability, heat resistance, fatigue strength and so on should be guaranteed for precision machining and tool life. Currently, it is hard to restore the recycled tungsten carbide powder entirely as raw material for new processed cemented carbide tool. In this study, to suggest positive use of recycled tungsten carbide powder, we have tried to fabricate a carbon based sintered steel which shows reinforced mechanical properties with recycled tungsten carbide powder. We have made set of newly designed sintered steels. Compression test of sintered specimen in density ratio of 0.85 (which means 15% porosity inside) has been conducted. As results, at least 1.7 times higher in nominal strength in the amount of 7.0 wt.% was shown in recycled WC powder. The strength reached to over 600 MPa for the Fe-WC-Co-Cu sintered alloy. Wear test has been conducted by using ball-on-disk type friction tester using 5 mm diameter ball with normal force of 2 N in the dry conditions. Wear amount after 1,000 m running distance shows that about 1.5 times longer life was shown in designed sintered alloy. Since results of tensile test showed that same tendency in previous testing, it is concluded that designed sintered alloy can be used for several mechanical parts with special strength and anti-wear ability in relatively low cost due to recycled tungsten carbide powder.

Keywords: Tungsten carbide, recycle process, compression test, powder metallurgy, anti-wear ability.

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Authors: Abbaas I. Kareem, H. Nikraz

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The use of recycled concrete aggregates (RCAs) in hot-mix asphalt (HMA) production could ease natural aggregate shortage and maintain sustainability in modern societies. However, it was the attached cement mortar and other impurities that make the RCAs behave differently than high-quality aggregates. Therefore, different upgrading treatments were suggested to enhance its properties before being used in HMA production. Disappointedly, some of these treatments had caused degradation to some RCA properties. In order to avoid degradation, a coating technique is developed. This technique is based on combining of two main treatments, so it is named as double coating technique (DCT). Dosages of 0%, 20%, 40% and 60% uncoated RCA, RCA coated with Cement Slag Paste (CSP), and Double Coated Recycled Concrete Aggregates (DCRCAs) in place of granite aggregates were evaluated. The results indicated that the DCT improves strength and reduces water absorption of the DCRCAs compared with uncoated RCAs and RCA coated with CSP. In addition, the DCRCA asphalt mixtures exhibit stability values higher than those obtained for mixes made with granite aggregates, uncoated RCAs and RCAs coated with CSP. Also, the DCRCA asphalt mixtures require less bitumen to achieve the optimum bitumen content (OBC) than those manufactured with uncoated RCA and RCA-coated with CSP. Although the results obtained were encouraging, more testing is required in order to examine the effect of the DCT on performance properties of DCRCA- asphalt mixtures such as rutting and fatigue.

Keywords: Recycled concrete aggregates, hot mix asphalt, double coating technique, aggregate crashed value, Marshall parameters.

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Authors: Sallehan Ismail, Mahyuddin Ramli

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This study examined the properties of fresh and hardened concretes as influenced by the moisture state of the coarse recycled concrete aggregates (RCA) after surface treatment. Surface treatment was performed by immersing the coarse RCA in a calcium metasilicate (CM) solution. The treated coarse RCA was maintained in three controlled moisture states, namely, air-dried, oven-dried, and saturated surface-dried (SSD), prior to its use in a concrete mix. The physical properties of coarse RCA were evaluated after surface treatment during the first phase of the experiment to determine the density and the water absorption characteristics of the RCA. The second phase involved the evaluation of the slump, slump loss, density, and compressive strength of the concretes that were prepared with different proportions of natural and treated coarse RCA. Controlling the moisture state of the coarse RCA after surface treatment was found to significantly influence the properties of the fresh and hardened concretes. 

Keywords: Moisture state, recycled concrete aggregate, surface treatment.

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Authors: Merve Ozer, Tolga Gokkurt, Yasemen Gokkurt, Ezgi Bozbey

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In this study, research has been conducted on the recovery of automotive textile waste, which has heavy use in the automotive sector and consists of PET/PP content, through the upcycling technique of post-product and post-consumer usage. The aim is to investigate the formulation and production methods that will enable the substitution of original PP raw materials, used in the production of plastic edge bands, with PP/PET alloys. The lamination structure of the mentioned waste makes it impossible to separate the incompatible PP and PET phases, thereby hindering the production of high-quality raw materials or products through recycling. In this study, a comprehensive process was examined through a two-step production process using different types of block and maleic-grafted copolymers to achieve compatibility between these two incompatible phases. The obtained plastic raw materials, referred to as PP/PET blends, were examined in detail, with a focus on their mechanical, thermal, and morphological properties, to discuss their substitutability for the original raw materials.

Keywords: Twin screw extruders, mechanical recycling, melt blending, plastic blends, polyethylene, polypropylene, recycling of plastics.

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Authors: Napoleana-Anna Chaliasou, Andrew Heath, Kevin Paine

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Fly ash-slag based Geopolymer Cement (GPC) is presenting mechanical properties and environmental advantages that make it the predominant “green” alternative to Portland Cement (PC). Although numerous life-cycle analyses praising its environmental advantages, disposal after the end of its life remains as an issue that has been barely explored. The present study is investigating the recyclability of fly ash-slag GPC as aggregate in mortars. The purpose of the study was to evaluate the effect of GPC fine Recycled Aggregates (RA), at replacement levels of 25% and 50%, on the main mechanical properties of PC and GPC mortar mixes. The results were compared with those obtained by corresponding mixes incorporating natural and PC-RA. The main physical properties of GPC-RA were examined and proven to be comparable to those of PC-RA and slightly inferior to those of natural sand. A negligible effect was observed at 28-day compressive and flexural strength of PC mortars with GPC aggregates having a milder effect than PC. As far as GPC mortars are concerned, the influence of GPC aggregates was enhancing for the investigated mechanical properties. Additionally, a screening test showed that recycled geopolymer aggregates are not prone of inducing alkali silica reaction.

Keywords: Concrete recycling, geopolymer cement, recycled concrete aggregates, sustainable concrete technology.

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Authors: Esra Yel, Tabriz Aslanov, Merve Sogancioglu, Suheyla Kocaman, Gulnare Ahmetli

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The disposal of waste plastics has become a major worldwide environmental problem. Pyrolysis of waste plastics is one of the routes to waste minimization and recycling that has been gaining interest. In pyrolysis, the pyrolysed material is separated into gas, liquid (both are fuel) and solid (char) products. All fractions have utilities and economical value depending upon their characteristics. The first objective of this study is to determine the co-pyrolysis product fractions of waste HDPE- (high density polyethylene) and LDPE (low density polyethylene)-olive pomace (OP) and to determine the qualities of the solid product char. Chars obtained at 700 °C pyrolysis were used in biocomposite preparation as additive. As the second objective, the effects of char on biocomposite quality were investigated. Pyrolysis runs were performed at temperature 700 °C with heating rates of 5 °C/min. Biocomposites were prepared by mixing of chars with bisphenol-F type epoxy resin in various wt%. Biocomposite properties were determined by measuring electrical conductivity, surface hardness, Young’s modulus and tensile strength of the composites. The best electrical conductivity results were obtained with HDPE-OP char. For HDPE-OP char and LDPE-OP char, compared to neat epoxy, the tensile strength values of the composites increased by 102% and 78%, respectively, at 10% char dose. The hardness measurements showed similar results to the tensile tests, since there is a correlation between the hardness and the tensile strength.

Keywords: Pyrolysis, olive pomace, char, biocomposite, PE plastics.

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Authors: N. Stevulova, I. Schwarzova, V. Hospodarova, J. Junak, J. Briancin

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Sustainability is becoming a priority for developers and the use of environmentally friendly materials is increasing. Nowadays, the application of raw materials from renewable sources to building materials has gained a significant interest in this research area. Lignocellulosic aggregates and cellulosic fibers are coming from many different sources such as wood, plants and waste. They are promising alternative materials to replace synthetic, glass and asbestos fibers as reinforcement in inorganic matrix of composites. Natural fibers are renewable resources so their cost is relatively low in comparison to synthetic fibers. With the consideration of environmental consciousness, natural fibers are biodegradable so their using can reduce CO₂ emissions in the building materials production. The use of cellulosic fibers in cementitious matrices have gained importance because they make the composites lighter at high fiber content, they have comparable cost - performance ratios to similar building materials and they could be processed from waste paper, thus expanding the opportunities for waste utilization in cementitious materials. The main objective of this work is to find out the possibility of using different wastes: hemp hurds as waste of hemp stem processing and recycled fibers obtained from waste paper for making cement composite products such as mortars based on cellulose fibers. This material was made of cement mortar containing organic filler based on hemp hurds and recycled waste paper. In addition, the effects of fibers and their contents on some selected physical and mechanical properties of the fiber-cement plaster composites have been investigated. In this research organic material have used to mortars as 2.0, 5.0 and 10.0 % replacement of cement weight. Reference sample is made for comparison of physical and mechanical properties of cement composites based on recycled cellulosic fibers and lignocellulosic aggregates. The prepared specimens were tested after 28 days of curing in order to investigate density, compressive strength and water absorbability. Scanning Electron Microscopy examination was also carried out.

Keywords: Hemp hurds, organic filler, recycled paper, sustainable building materials.

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Authors: Iveta Nováková, Martin-Andrè S. Husby, Boy-Arne Buyle

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The building industry has one of the most significant contributions to global warming due to the production of building materials, transportation, building activities, and demolition of structures when they reach the end of their life. Implementation of circular material flow and circular economy can significantly reduce greenhouse gasses and simultaneously reduce the need for natural resources. The use of recycled concrete aggregates (RCA) is one of the possibilities for reducing the depletion of raw materials for concrete production. Concrete is the most used building material worldwide, and aggregates constitute large part of its volume. RCA can replace a certain amount of natural aggregates (NA), and concrete will still perform as required. The aim of this scientific paper is to evaluate RCA properties with and without mechanical treatment. Analysis of RCA itself will be followed by compressive strength of concrete containing various amounts of treated and non-treated RCA. Results showed improvement in compressive strength of the mix with mechanically treated RCA compared to standard RCA, and even the strength of concrete with mechanically treated RCA in dose 50% of coarse aggregates was higher than the reference mix by 4%. Based on obtained results, it can be concluded that integration of RCA in industrial concrete production is feasible, at a replacement ratio of 50% for mechanically treated RCA and 30% if untreated RCA is used, without affecting the compressive strength negatively.

Keywords: Recycled concrete aggregates, RCA, mechanical treatment, aggregate properties, compression strength.

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Authors: K. Kuntanoo, S. Promkotra, P. Kaewkannetra

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According to synthetic plastics obtained from petroleum cause some environmental problems. Therefore, degradable plastics become widely used and studied for replacing the synthetic plastic waste. A biopolymer of poly hydroxybutyrate-co-hydroxyvalerate (PHBV) is subgroups of a main kind of polyhydroxyalkanoates (PHAs). Naturally, PHBV is hard, brittle and low flexible while natural rubber (NR) is high elastic latex. Then, they are blended and the biodegradation of the blended PHBV and NR films were examined in soil environment. The results showed that the degradation occurs predominantly in the bulk of the samples. The order of biodegradability was shown as follows: PHBV> PHBV/NR> NR. After biodegradation, the blended films were characterized by appearance analysis such as Scanning Electron Microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). It was found that the biodegradation mainly occurred at the polymer surface.

Keywords: Biodegradation, polyhydroxyalkanoates (PHAs), Polyhydroxybutyrate-co-hydroxyvalerate (PHBV), natural rubber (NR).

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Authors: Nikol Žižková

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The aim of this study was to observe the behavior of polymer-modified cement mortars with regard to the use of a pozzolanic admixture. Polymer-modified mortars (PMMs) containing various types of waste glass (waste packing glass and fluorescent tube glass) were produced always with 20% of cement substituted with a pozzolanic-active material. Ethylene/vinyl acetate copolymer (EVA) was used for polymeric modification. The findings confirm the possibility of using the waste glass examined herein as a partial substitute for cement in the production of PMM, which contributes to the preservation of non-renewable raw material resources and to the efficiency of waste glass material reuse.

Keywords: Recycled waste glass, polymer-modified mortars, pozzolanic admixture.

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Authors: Parizad Sheikhi, Mohammad Talaeipour

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the effects of refining and alkaline chemicals on potential of recycling bleached chemical pulp of bagasse were investigated in this study. Recycling was done until three times. Handsheet properties such as, apparent density, light scattering coefficient, tear index, burst index, breaking length, and fold number according to TAPPI standard were measured. Water retention value also was used to considering the treatments during recycling. Refining enhanced the strength of recycled pulp by increasing fiber flexibility and swelling ability, whereas by applying chemical treatment didn't observe any improvement. The morphology of recycled fiber was considered with scanning electron microscopy (SEM).

Keywords: Bagasse pulp, chemical treatment, recycling, refining, scanning electron microscopy, water retention value.

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Authors: A.K. Birru, D Benny Karunakar, M. M. Mahapatra

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Recycling of aluminum alloys often decrease fluidity, consequently influence the castability of the alloy. In this study, the fluidity of Al-Zn alloys, such as the standard A713 alloy with and without scrap addition has been investigated. The scrap added was comprised of contaminated alloy turning chips. Fluidity measurements were performed with double spiral fluidity test consisting of gravity casting of double spirals in green sand moulds with good reproducibility. The influence of recycled alloy on fluidity has been compared with that of the virgin alloy and the results showed that the fluidity decreased with the increase in recycled alloy at minimum pouring temperatures. Interestingly, an appreciable improvement in the fluidity was observed at maximum pouring temperature, especially for coated spirals.

Keywords: A713 alloy, Fluidity, Hexachloroethane, Pouring temperature, Recycling.

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Authors: C. Alexandridou, G. N. Angelopoulos, F. A. Coutelieris

Abstract:

Construction industry in Greece consumes annually more than 25 million tons of natural aggregates originating mainly from quarries. At the same time, more than 2 million tons of construction and demolition waste are deposited every year, usually without control, therefore increasing the environmental impact of this sector. A potential alternative for saving natural resources and minimize landfilling, could be the recycling and re-use of Concrete and Demolition Waste (CDW) in concrete production. Moreover, in order to conform to the European legislation, Greece is obliged to recycle non-hazardous construction and demolition waste to a minimum of 70% by 2020. In this paper characterization of recycled materials - commercially and laboratory produced, coarse and fine, Recycled Concrete Aggregates (RCA) - has been performed. Namely, X-Ray Fluorescence and X-ray diffraction (XRD) analysis were used for chemical and mineralogical analysis respectively. Physical properties such as particle density, water absorption, sand equivalent and resistance to fragmentation were also determined. This study, first time made in Greece, aims at outlining the differences between RCA and natural aggregates and evaluating their possible influence in concrete performance. Results indicate that RCA’s chemical composition is enriched in Si, Al, and alkali oxides compared to natural aggregates. X-ray diffraction (XRD) analyses results indicated the presence of calcite, quartz and minor peaks of mica and feldspars. From all the evaluated physical properties of coarse RCA, only water absorption and resistance to fragmentation seem to have a direct influence on the properties of concrete. Low Sand Equivalent and significantly high water absorption values indicate that fine fractions of RCA cannot be used for concrete production unless further processed. Chemical properties of RCA in terms of water soluble ions are similar to those of natural aggregates. Four different concrete mixtures were produced and examined, replacing natural coarse aggregates with RCA by a ratio of 0%, 25%, 50% and 75% respectively. Results indicate that concrete mixtures containing recycled concrete aggregates have a minor deterioration of their properties (3-9% lower compression strength at 28 days) compared to conventional concrete containing the same cement quantity.

Keywords: Chemical and physical characterization, compressive strength, mineralogical analysis, recycled concrete aggregates, waste management.

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Authors: Wuthichai Wongthatsanekorn

Abstract:

Plastic waste is a big issue in Thailand, but the amount of recycled plastic in Thailand is still low due to the high investment and operating cost. Hence, the rest of plastic waste are burnt to destroy or sent to the landfills. In order to be financial viable, an effective reverse logistics infrastructure is required to support the product recovery activities. However, there is a conflict between reducing the cost and raising environmental protection level. The purpose of this study is to build a goal programming (GP) so that it can be used to help analyze the proper planning of the Thailand-s plastic recycling system that involves multiple objectives. This study considers three objectives; reducing total cost, increasing the amount of plastic recovery, and raising the desired plastic materials in recycling process. The results from two priority structures show that it is necessary to raise the total cost budget in order to achieve targets on amount of recycled plastic and desired plastic materials.

Keywords: Goal Programming, Plastic Recycling, Thailand.

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Authors: Ahmed I. Shehab, Sabah M. Abdel Basir, M. A. Abdel Khalek, M. H. Soliman, G. Elgemeie

Abstract:

Spent bleaching earth (SBE) recycling and utilization as an adsorbent to eliminate dyes from aqueous solution was studied. Organic solvents and subsequent thermal treatment were carried out to recover and reactivate the SBE. The effect of pH, temperature, dye’s initial concentration, and contact time on the dye removal using recycled spent bleaching earth (RSBE) was investigated. Recycled SBE showed better removal affinity of cationic than anionic dyes. The maximum removal was achieved at pH 2 and 8 for anionic and cationic dyes, respectively. Kinetic data matched with the pseudo second-order model. The adsorption phenomenon governing this process was identified by the Langmuir and Freundlich isotherms for anionic dye while Freundlich model represented the sorption process for cationic dye. The changes of Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were computed and compared through thermodynamic study for both dyes.

Keywords: Spent bleaching earth, Regeneration, Dye removal, Thermodynamics.

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