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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Performance Evaluation of Recycled Asphalt Shingles (RAS) in Hot Mix Asphalt (HMA): An Ontario Perspective

Islam, Riyad-UL 07 April 2011 (has links)
Today, a large quantity of waste is generated from the replacement of residential and commercial roofs. Many of the roofs being upgraded with previously constructed from asphalt shingles. Recycled Asphalt Shingles (RAS) contain nearly 30% of asphalt cement by mass, which can be a useful additive to asphalt pavements. In addition, shingles can offer significant potential savings through recycling and recovery as a construction material in flexible pavement. Currently, one and a half million tons of roofing shingle waste is generated each year in Canada related to the replacement of residential and commercial roofs and 90% of this valuable material is sent to landfills. If engineered properly, the addition of RAS into Hot Mix Asphalt (HMA) can provide significant benefits. The University of Waterloo’s Centre for Pavement and Transportation Technology (CPATT) is committed to working with public and private sector partners to develop sustainable technologies for the pavement industry. Using RAS in HMA can lead to economical, environmental and social benefits. Examples of which are reduced waste going to landfills and a reduction in the quantity of virgin material required. This research has involved the Ontario Centres of Excellence (OCE) and Miller Paving Limited. It was conducted to evaluate the performance of HMA containing RAS in both field and laboratory tests. A varying percentage of RAS was added to six common Ontario surface and binder layer of asphalt mixes. The intent was to determine if RAS could be added to improve performance and provide longer term cost savings. Laboratory testing was performed to evaluate the mix behavior. The elastic properties, fatigue life and resistance to thermal cracking were all evaluated at the CPATT laboratory. The characteristics of the mixes were evaluated by carrying out Dynamic Modulus, Resilient Modulus, Flexural Fatigue and Thermal Stress Restrained Specimen Test (TSRST) tests following American Association of State Highway and Transportation Officials (AASHTO) and American Society for Testing and Materials (ASTM) standards. Field test sections were constructed from HMA containing RAS to monitor the pavement behavior under natural environmental and traffic loading conditions. Evaluation of the field sites was performed using a Portable Falling Weight Deflectometer (PFWD) and carrying out distress surveys following the Ministry of Transportation Ontario (MTO) guidelines. The results to date show the sections performing very well with minimal to no distress developing. The results of the laboratory testing and field performance evaluations have shown encouraging results for the future use of RAS in HMA. If RAS can properly be engineered into HMA it can be a useful additive in both the surface and binder layers of the flexible pavement structure. Ultimately, the use of RAS in HMA can provide both an environmentally friendly and cost effective solution to the Ontario paving industry.
52

Evaluation of the Effect of Recycled Asphalt Shingles on Ontario Hot Mix Pavement

Ddamba, Shirley Jacqueline 23 September 2011 (has links)
Due to the 15-20 year life span of roofing shingles, 1.5 million tonnes of asphalt roofing shingles are being demolished and replaced annually in Canada from both residential and commercial facilities. These roofing shingles are manufactured from very high quality materials which are considered a valuable by-product. Recycled Asphalt Shingles (RAS), a product containing approximately 30% asphalt cement by mass, is a valuable additive to Hot Mix Asphalt (HMA) pavements and a potential savings for the construction industry. Recycling of demolished asphalt shingles is a significant new step forward in abating the need to put the waste into landfills. This re-use creates a great opportunity in reducing materials being dumped at landfills while providing an additive to HMA mixtures for paving. Therefore, this leads to economic, environmental, and social benefits for all the stakeholders and road users such as reduced need for landfill space, conservation of virgin materials and environment, and financial saving. The research involved evaluating the use of demolished shingles in six typical Ontario Hot Mix Asphalt (HMA) mixtures; HL 3 (1.5% RAS, 13.5% RAP), binder layer mixes SP19 (6% RAS, and 3% RAS, 25% RAP), surface layer mixes SP12.5 FC 1(3% RAS, 17% RAP) and SP12.5 FC2 (6% RAS and 3% RAS, 12% RAP). The six HMA mixes were also designed to contain Recycled Asphalt Pavement (RAP). This further complicated the research as both RAP and RAS were added. All mixes were designed and tested at CPATT laboratory; in addition a test section was paved at the CPATT Test Track. This research involved both laboratory and field evaluations of mixes containing RAS to develop pavement performance modeling for all six mixes using the updated Mechanistic-Empirical Pavement Design Guide (MEPDG). A life-cycle assessment of the six HMA mixes was performed to quantify the environmental impacts using the Pavement Life-Cycle Assessment Tool for Environmental and Economic Effects (PaLATE) and rigorous economic costs/benefits were assessed using Life Cycle Cost Analysis (LCCA). Calibrations of models for Ontario conditions were completed. Test slabs were also constructed to simulate climatic changes by running freeze-thaw cycles based on weather data over the past ten years. Three field test sections located in the Town of Markham and one at the CPATT Test Track were monitored and assessed under as part of the research. Regular pavement condition assessments were carried out on all the test sections by performing non-destructive tests using a Portable Falling Weight Deflectometer (PFWD) and distress survey in accordance with the Ministry of Transportation (MTO) guidelines. The CPATT Test Track was evaluated with both the PFWD and surface distresses, whereas only distress surveys were performed on the three residential streets in the Town of Markham. The evaluations demonstrated that the pavements were in good conditions throughout the monitoring period of the research (four years for the three residential streets in the Town of Markham and two years for the CPATT Test Track). The structural analysis using the MEPDG indicated that Mix 3: SP19 3% RAS and 25% RAP had the best performance followed by Mix 2: SP19 6% RAS when considering all factors in the Life-Cycle Assessment. Mix 3 exhibited maximum savings on environmental emissions, energy and water usage, best adoptability to climatic change and skid resistance properties with minimal life cycle costs. The pavement performance and life-cycle assessment modeling demonstrated encouraging results for the use of RAS in HMA pavements from which guidelines were developed for its use. It is important to note that careful mix design should be carried out when RAS is added to HMA especially when RAP is also used. This includes measuring of all key properties especially at low and high temperatures. In short, RAS can be a valuable additive in both surface and binder layers of HMA pavements. It provides an environmentally friendly and cost-effective innovation for the Ontario paving industry and can be considered for usage elsewhere with appropriate engineering.
53

Evaluation of Recycled Concrete Aggregate Performance in Structural Concrete

Butler, Liam January 2012 (has links)
Sustainable resource management and development have been at the forefront of important issues concerning the construction industry for the past several years. Specifically, the use of sustainable building materials and the reuse and recycling of previously used building materials is gaining acceptance and becoming common place in many areas. As one of the most commonly used building materials in the world, concrete, composed of aggregate, sand, cement and water, can be recycled and reused in a variety of applications. Using crushed concrete as fill and subgrade material under roads, sidewalks and foundations has been the most common of these applications. However, research has been ongoing over the past 50 years in many countries including Germany, Canada, Japan, the United States, China, and Australia investigating the use of crushed concrete from demolished old concrete structures to fully or partially replace the virgin aggregate used to produce new concrete for use in building and pavement applications. Producing concrete using recycled concrete aggregates (RCAs) has several advantages, namely, the burden placed on non-renewable aggregate resources may be significantly decreased, the service life and capacity of landfill and waste management facilities can be extended, and the carbon dioxide emissions and traffic congestion associated with the transport of virgin aggregates from remote sites can be reduced. This research is directed at benchmarking typical RCA sources for usage in structural concrete and investigating the inter-relationships between aggregate properties, concrete properties and the bond properties between reinforcing steel and RCA concrete. The experimental program focused on four main areas: aggregate properties testing, development of concrete mixture proportions, concrete fresh and hardened properties testing, and beam-end bond testing. Four coarse aggregate sources were investigated including one virgin or natural aggregate (NA) source, and three RCA sources. Two RCA sources were derived from the crushing of decommissioned building and pavement structures (RCA-1 and RCA-2) while the third source was derived from the crushing of returned ready-mix concrete (RCA-3). A variety of typical and non-typical aggregate tests were performed to provide a basis for correlation with fresh and hardened concrete properties results. A total of 24 concrete mixtures were developed and divided into three separate categories, 1) control, 2) direct replacement, and 3) strength-based mixtures. The control mixtures were proportioned to achieve compressive strengths of 30, 40, 50 and 60MPa with slump values between 75 and 125 mm and served as a basis for comparison with the RCA concrete mixtures. The direct replacement mixtures were developed to investigate the effect that fully replacing (i.e., 100% replacement by volume) virgin coarse aggregate with RCA has on the fresh and hardened properties of the resulting concrete. The strength-based mixtures were developed to investigate the influence of aggregate properties on reinforcement bond in concrete having the same compressive strength. In addition, two separate experimental phases were carried out which had varying compressive strength ranges, different RCA sources, and different suppliers of the same type GU cement. Concrete properties such as slump, compressive strength, splitting tensile strength, modulus of elasticity, Poisson’s ratio, linear coefficient of thermal expansion (LCTE), modulus of rupture and fracture energy were all measured. In total, 48 beam-end specimens were tested that incorporated three bonded lengths (125, 375, and 450 mm) and four concrete compressive strengths (30, 40, 50 and 60 MPa). Based on the results of the aggregate testing it was found that concrete incorporating pre-soaked (i.e., fully saturated) RCA as a 100% replacement for natural aggregate had slump values between 22% and 75%, compressive strengths between 81% and 137%, splitting tensile strengths between 78% and 109%, modulus of elasticity values between 81% and 98%, LCTE values in the same range, flexural strengths between 85% and 136%, and fracture energies between 68% and 118%, of the equivalent control (natural aggregate) concrete mixture. Overall, reductions in bond strength between natural aggregate and RCA concrete ranged between 3 and 21%. The strength of coarse aggregate as quantified by the aggregate crushing value (ACV) was found to be the most significant aggregate property for influencing bond strength. A regression model (based on the beam-end specimens test results) was developed to extrapolate the experimental development lengths as a function of f’c1/4 and ACV. The model, while not intended for use as a design equation, predicted that the required development lengths for the RCA concrete tested as part of this research study were up to 9% longer as compared to the natural aggregate concrete. A detailed flowchart of the various inter-relationships between aggregate properties, concrete properties and reinforced concrete bond properties was compiled based on the results of this research. A comprehensive guideline for use of RCA in concrete was developed based on the findings of this research. It includes a systematic decision tree approach for assessing whether a particular RCA source can be categorized into one of three performance classes. The range of allowable applications of a concrete which incorporates the RCA source as replacement of natural coarse aggregate will depend on the RCA performance class.
54

Analysing the critical design parameters for reuse

Ibbotson, Scott, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW January 2006 (has links)
Reuse of components as opposed to material recovery, recycling or disposal has been identified as one of the most efficient EOL strategies for products. The concept behind reuse is that some components and subassemblies have a design life that exceeds the life of the product itself. In order for reuse to be successfully implemented as an EOL strategy, a designer needs to incorporate into a product a philosophy of Design for Reuse (DfRe) at the early design stage. Reliable methods to assess the remaining life of used components based on a products usage life are also required. Furthermore, current industry practices and literature advocate that there is no methodology to decide which parameters need to be redesigned so as to change the life of a selected component to a desired level. The objective of this research is to develop a methodology to assess the reuse potential of product groups based on component failure mechanisms and their associated critical lifetime prediction design parameters. Utilising these clustered groups mathematical models were then developed to establish the useful life of the components for each clustered group. Finally, a means of equating useful life to design life was established and the relationship between, the failure mechanisms, critical lifetime prediction design parameters and design life were represented in graphical format. In order to achieve the proposed objective, Cluster analysis, in particular Group Technology (GT) and Hierarchical clustering were employed to group components with similar failure mechanisms. Following this, multiple linear regression was used to establish mathematical models based on condition monitoring data for each of the clustered groups and their related critical lifetime prediction design parameters. A sensitivity analysis was conducted using the mathematical models, in order to produce graphical relations between the useful life and design parameters of a product. The validity of the suggested methodology was tested on electric motors and a gearbox as both these components have demonstrated great reuse potential. The results demonstrate that the methodology can assist designers in estimating the design life and associated design parameters with great accuracy, and subsequently aiding in a stratagem for reuse.
55

Analysing the critical design parameters for reuse

Ibbotson, Scott, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW January 2006 (has links)
Reuse of components as opposed to material recovery, recycling or disposal has been identified as one of the most efficient EOL strategies for products. The concept behind reuse is that some components and subassemblies have a design life that exceeds the life of the product itself. In order for reuse to be successfully implemented as an EOL strategy, a designer needs to incorporate into a product a philosophy of Design for Reuse (DfRe) at the early design stage. Reliable methods to assess the remaining life of used components based on a products usage life are also required. Furthermore, current industry practices and literature advocate that there is no methodology to decide which parameters need to be redesigned so as to change the life of a selected component to a desired level. The objective of this research is to develop a methodology to assess the reuse potential of product groups based on component failure mechanisms and their associated critical lifetime prediction design parameters. Utilising these clustered groups mathematical models were then developed to establish the useful life of the components for each clustered group. Finally, a means of equating useful life to design life was established and the relationship between, the failure mechanisms, critical lifetime prediction design parameters and design life were represented in graphical format. In order to achieve the proposed objective, Cluster analysis, in particular Group Technology (GT) and Hierarchical clustering were employed to group components with similar failure mechanisms. Following this, multiple linear regression was used to establish mathematical models based on condition monitoring data for each of the clustered groups and their related critical lifetime prediction design parameters. A sensitivity analysis was conducted using the mathematical models, in order to produce graphical relations between the useful life and design parameters of a product. The validity of the suggested methodology was tested on electric motors and a gearbox as both these components have demonstrated great reuse potential. The results demonstrate that the methodology can assist designers in estimating the design life and associated design parameters with great accuracy, and subsequently aiding in a stratagem for reuse.
56

Creep Characteristics and Shear Strength of Recycled Asphalt Blends

January 2011 (has links)
abstract: The trend towards using recycled materials on new construction projects is growing as the cost for construction materials are ever increasing and the awareness of the responsibility we have to be good stewards of our environment is heightened. While recycled asphalt is sometimes used in pavements, its use as structural fill has been hindered by concern that it is susceptible to large long-term deformations (creep), preventing its use for a great many geotechnical applications. While asphalt/soil blends are often proposed as an alternative to 100% recycled asphalt fill, little data is available characterizing the geotechnical properties of recycled asphalt soil blends. In this dissertation, the geotechnical properties for five different recycled asphalt soil blends are characterized. Data includes the particle size distribution, plasticity index, creep, and shear strength for each blend. Blends with 0%, 25%, 50%, 75% and 100% recycled asphalt were tested. As the recycled asphalt material used for testing had particles sizes up to 1.5 inches, a large 18 inch diameter direct shear apparatus was used to determine the shear strength and creep characteristics of the material. The results of the testing program confirm that the creep potential of recycled asphalt is a geotechnical concern when the material is subjected to loads greater than 1500 pounds per square foot (psf). In addition, the test results demonstrate that the amount of soil blended with the recycled asphalt can greatly influence the creep and shear strength behavior of the composite material. Furthermore, there appears to be an optimal blend ratio where the composite material had better properties than either the recycled asphalt or virgin soil alone with respect to shear strength. / Dissertation/Thesis / M.S. Civil Engineering 2011
57

Caracterização do linter reciclado de algodão: alternativa sustentável para à produção de celulose / Characterization of linter recycled cotton: sustainable alternative for the pulp and paper production

Kumabe, Fabricio Junki Blanco [UNESP] 05 September 2016 (has links)
Submitted by FABRÍCIO JUNKI BLANCO KUMABE null (fabricio.kumabe@hotmail.com) on 2016-11-04T13:03:14Z No. of bitstreams: 1 Fabricio Kumabe_com ficha.pdf: 1115598 bytes, checksum: 196f145bae6a5843904962434297ec02 (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO null (luizaromanetto@hotmail.com) on 2016-11-10T13:36:20Z (GMT) No. of bitstreams: 1 kumare_fjb_me_bot.pdf: 1105585 bytes, checksum: a9695cfcf41b73428ec6772af141364a (MD5) / Made available in DSpace on 2016-11-10T13:36:20Z (GMT). No. of bitstreams: 1 kumare_fjb_me_bot.pdf: 1105585 bytes, checksum: a9695cfcf41b73428ec6772af141364a (MD5) Previous issue date: 2016-09-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho teve como objetivo determinar as propriedades físicas, químicas e anatômicas do linter residual de algodão (linter reciclado Blue 40, Blue 30, e Alvejado 30), oriundo da indústria têxtil. Para à caracterização foram coletadas três amostras, onde se analisou teor de umidade, densidade aparente, teor de holocelulose, extrativos totais, lignina, número kappa e solubilidade em NaOH 1 e 5%, em água quente e água fria, teor de cinzas, e determinação das dimensões das fibras e relações entre as dimensões de fibras, todas as análises procederam de acordo com as normas da TAPPI. Na avaliação física da: umidade, as médias dos tratamentos não apresentaram diferença significativa. Para densidade aparente houve diferença estatística entre os tratamentos Blue 30 e Blue 40. Já a avaliação do teor holocelulose os tratamentos foram diferentes, Blue 40 apresentou a maior média. Para avaliação do teor de extrativos foram encontrados valores de 6,40%, 5,02% e 3,05% para os tratamentos Blue 30, 40 e Alvejado 30, no qual o Blue 30 é estatisticamente diferente do Alvejado 30 e o Blue 40 semelhante a ambos, respectivamente. O teor de lignina do Blue 40 apresentou a menor média, seguido do tratamento Blue 30 e Alvejado. A porcentagem de cinzas no Blue 40 foi superior comparado aos outros tratamentos. Na avaliação da solubilidade em NaOH 1%, os tratamentos Blue 30 e Alvejado 30 apresentaram médias iguais, já o tratamento Blue 40 apresentou resultado inferior. A solubilidade em NaOH 5% os tratamentos Blue 30 e Blue 40 apresentaram médias iguais, diferentes do Alvejado 30. Os valores de solubilidade em água fria foram iguais para o Blue 40 e Alvejado 30 e superiores ao Blue 30. Os valores de solubilidade em água quente foram iguais para Blue 30 e Alvejado 30 e superiores ao Blue 40 (1,84%). Sendo assim conclui-se que a Blue 40 apresentou melhores características química, física e anatômica para produção de celulose. / This study aimed to determine the physical, chemical and anatomical residual cotton linters (linters Recycled Blue 40, Blue 30, and Targeted 30) from the textile industry. For the characterization Three samples were collected, which were analyzed moisture content, bulk density, holocellulose content, extractives, lignin, kappa number and solubility in NaOH 1 and 5% in hot water and cold water, ash content, and determination of fiber dimensions and relationships between the fiber dimensions, all analyzes conducted according to the standards of TAPPI. In the physical evaluation of: humidity, the treatment means no significant difference. For apparent density was no statistical difference between treatments Blue 30 and Blue 40. Since the assessment of the content holocelulose treatments were different, Blue 40 had the highest average. To evaluate the extractives content were found values of 6.40%, 5.02% and 3.05% for treatments Blue 30, 40 and Targeted 30, wherein Blue 30 is statistically different from Targeted 30, and Blue 40 similarly to both, respectively. The lignin content of the Blue 40 had the lowest average, followed by the treatment Blue 30 and Targeted. The percentage of ash in Blue 40 was higher compared to other treatments. In assessing the solubility of NaOH 1%, treatments Blue 30 and 30 Targeted had equal means, since the treatment Blue 40 showed lower results. The solubility in NaOH 5% and the Blue 30 Blue 40 treatments showed equal means, different Targeted 30. The solubility values were equal in cold water for Targeted Blue 40 and 30 and the upper Blue 30. The water-solubility figures hot were equal to 30 and Blue Targeted 30 and above the Blue 40 (1.84%). Therefore, it is concluded that Blue 40 showed better chemical characteristics, physical and anatomical for pulp production.
58

Utilização de resíduos de concreto em concreto auto-adensável /

Branco, Roberto Pagliosa. January 2012 (has links)
Orientador: Antonio Anderson da Silva Segantini / Coorientador: Marco Antonio Morais Alcantara / Banca: José Luiz Pinheiro Melges / Banca: Cesar Fabiano Fioriti / Resumo: O principal objetivo desse trabalho é buscar uma solução que viabilize melhorar as características do concreto auto-adensável (CAA) e que também possibilite o reaproveitamento dos resíduos gerados pela indústria da construção civil. O trabalho consiste em produzir CAA com adição de material fino constituído por resíduos de concreto em substituição ao agregado miúdo, objetivando obter uma mistura auto- adensável sem segregação, cujo resultado seja benéfico para as propriedades físicas e mecânicas do concreto. Para tanto, foram realizados ensaios visando a avaliar as propriedades do concreto no estado fresco, segundo o método proposto por Tutikian (2004), a fim de otimizar a sua resistência no estado endurecido com o menor custo possível. E ainda, examinar diferentes faixas granulométricas procurando uma correlação que propicie condições adequadas de trabalhabilidade e de resistência mecânica. Os ensaios ocorreram no Laboratório de Engenharia Civil da UNESP e no Laboratório CESP de Engenharia Civil em Ilha Solteira-SP. Os concretos confeccionados com resíduo mostraram-se viáveis por apresentarem resultados próximos ao do concreto usado como referência, fazendo com que os resíduos sejam uma ótima opção como material reciclável / Abstract: The main objective of this paper is to search for a solution that makes possible to improve the characteristics of the self-compacting concrete(SCC) and also allows the reuse of the waste generated by the construction industry civil. The work is to produce SCC with the addition of fine material consisting of concrete waste to replace the fine aggregate in order to obtain a compacting mixture without self- segregation; the result is beneficial for physical and mechanical properties of concrete. To this end, tests were carried out in order to evaluate the properties of fresh concrete, according to the method proposed by Tutikian (2004), in order to optimize its resistance in the hardened condition with the lowest possible cost. And also examining different granulometric compositions in order to look for a correlation that provides appropriated working conditions and mechanical strength. The trials took place at the Laboratory of Civil Engineering of UNESP and at CESP Laboratory of Civil Engineering of Ilha Solteira-SP. The concrete made from waste appear to be viable because presents results close to the concrete used as a reference, so that residues shall be a great choice as recyclable material / Mestre
59

Use of recycled broken bricks as Partial Replacement Coarse Aggregate for the Manufacturing of Sustainable Concrete

Pinchi, S., Pinchi, S., Ramírez, J., Rodríguez, J., Eyzaguirre, C. 28 February 2020 (has links)
The bricks are one of the primary materials required for construction of homes that no used completely when executes all the walls due, the excess purchase, the cutting to be settle, the breaking for their transfer and its fixed dimensions; this situation requires monitoring on work site the order, cleanliness and accidents. A common practice is these bricks and/or waste are included in the clearing construction before being deposited or eliminated in dumps or sanitary landfills, with their early clogging and shortening them to ther design lifespan. An important alternative to reduce this waste, is to recycle them and reuse them as a concrete component material, due to their high absorption percentage that allows them to keep the water inside of them and then use it in the cement hydration process as internal curing of the concrete. In the present investigation, the effect of crushed clay brick as a replacement for coarse aggregate in concrete processing is studied. The results indicate that with 21 % replacement brick, the plastic contraction decreases, and the compressive strength and flexural strength increase.
60

Control of fissures generated by the retraction in rigid pavements, applying synthetic fibers of recycled polypropylene.

Torres, V., Torres, V., Chirinos, K., Cuervo, C. 28 February 2020 (has links)
The retraction affects the setting process and the useful life of the concrete with the appearance of fissures; in last year's studies and methods have been generated to mitigate and control it with the use of different products and applications. The development of road infrastructure with the use of concrete as a rolling folder, requires methods to guarantee the durability and reduce the effects of the efforts incorporated by the use, climatic conditions, support base and restrictions of movement of the structure. To evaluate the effects of recycled synthetic polypropylene fibers in plastic retraction tests (ASTM C 1579), 3 mix designs were prepared with different ratios 58 gr., 116 gr., and 176 gr. of recycled and virgin synthetic fibers; the most significant and positive result to reduce fissures without affecting the resistance of concrete by bending and compression, was 0.50 mm without addition fibers, 0.10 mm and 0.15 mm with 176 gr. of virgin and recycled synthetic fibers. Finally, it can be concluded that adding a ratio of 4 kg per m3 allows good workability, in addition, the costs of the fibers are not representative compared to the high costs for future repairs.

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