• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 162
  • 136
  • 38
  • 21
  • 20
  • 20
  • 12
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 464
  • 157
  • 114
  • 91
  • 86
  • 84
  • 71
  • 68
  • 66
  • 65
  • 57
  • 56
  • 55
  • 52
  • 50
  • 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.
31

Influence of Type and Replacement Level of Recycled Aggregates on Concrete Properties.

Yang, Keun-Hyeok, Chung, H-S., Ashour, Ashraf January 2008 (has links)
Yes / Test results of nine recycled aggregate concretes and a control concrete using only natural aggregates are reported. The recycled aggregates used were classified into three different types according to their measured specific gravity and water absorption, namely, RG I for recycled coarse aggregate having a specific gravity of 2.53 and water absorption of 1.9%; RG III for recycled coarse aggregate having a specific gravity of 2.4 and water absorption of 6.2%; and RS II for recycled fine aggregate having a specific gravity of 2.36 and water absorption of 5.4%. The replacement levels of both recycled coarse and fine aggregates were 30, 50, and 100% in separate mixtures. Slump loss and the amount of bleeding with time were recorded for fresh concrete. Compressive and tensile strengths, moduli of rupture and elasticity, and unrestrained shrinkage strain were also measured for hardened concrete. The properties of fresh and hardened concrete tested, together with a comprehensive database reported in the literature, were evaluated with respect to the relative water absorption of aggregates combining the quality and volume of recycled aggregates used. In addition, the properties of hardened concrete with different replacement levels and quality of recycled aggregates were compared with the design equations of ACI 318-05 and empirical equations proposed by Oluokun for natural aggregate concrete, whenever possible. Test results clearly showed that the properties of fresh and hardened concrete containing recycled aggregates were dependent on the relative water absorption of aggregates. In addition, the moduli of rupture and elasticity of recycled aggregate concrete were lower than the design equations specified in ACI 318-05, when the relative water absorption of aggregates is above 2.5% and 3.0%, respectively.
32

Concreto com agregados graúdos reciclados de concreto : influência da idade de reciclagem nas propriedades dos agregados e concretos reciclados. / Concrete with recycled concrete coarse aggregates : influence of age of recycling in the properties of recycled aggregates and concretes

Buttler, Alexandre Marques 12 May 2003 (has links)
Os resíduos de concreto apresentam grande potencial para serem reciclados quando comparados com outros resíduos, entretanto, o número de estudos realizados no Brasil é muito pequeno dificultando a utilização deste material em dosagens estruturais. Em virtude disso, desenvolveu-se um estudo teórico-experimental visando caracterizar algumas propriedades do agregado e do concreto reciclado; no estudo teórico exploraram-se aspectos relacionados à geração, deposição, processos para recuperação, britagem, casos práticos, pesquisas envolvendo reciclados de concreto e as recomendações normativas existentes. No desenvolvimento experimental, analisou-se a influência do período decorrido entre a moldagem e a reciclagem do concreto nas propriedades dos agregados e concretos. Os resultados indicam que resíduos reciclados logo após sua geração, contribuem positivamente para as propriedades mecânicas do concreto, devido à existência de grande quantidade de partículas não-hidratadas de cimento, tais concretos obtiveram resultados superiores para a resistência à compressão e tração quando comparados aos concretos com agregados naturais. / The concrete residues show a large potential to be recycled when compared with other residues; however, the number of studies in Brazil is very small hindering the use of this material in structural dosage. By virtue of that, it was developed a theoretical-experimental study to characterize some properties of aggregate and recycled concrete; in the theoretical study it was explored aspects related to the generation, deposition, processes for recovery, crushing, practical cases, researches involving recycled of concrete and the existent normative recommendations. In the experimental development, it was analyzed the influence of the period elapsed between the molding and the recycling of the concrete in the properties of the aggregates and concretes. The results indicate that residues recycled soon after generation, these contribute positively to the mechanical properties of the concrete due to the existence of large amount of nonhydrated cement particles, such concretes obtained results superiors for the compression strenght and tensile strenght when compared to the concretes with natural aggregates.
33

Concreto com agregados graúdos reciclados de concreto : influência da idade de reciclagem nas propriedades dos agregados e concretos reciclados. / Concrete with recycled concrete coarse aggregates : influence of age of recycling in the properties of recycled aggregates and concretes

Alexandre Marques Buttler 12 May 2003 (has links)
Os resíduos de concreto apresentam grande potencial para serem reciclados quando comparados com outros resíduos, entretanto, o número de estudos realizados no Brasil é muito pequeno dificultando a utilização deste material em dosagens estruturais. Em virtude disso, desenvolveu-se um estudo teórico-experimental visando caracterizar algumas propriedades do agregado e do concreto reciclado; no estudo teórico exploraram-se aspectos relacionados à geração, deposição, processos para recuperação, britagem, casos práticos, pesquisas envolvendo reciclados de concreto e as recomendações normativas existentes. No desenvolvimento experimental, analisou-se a influência do período decorrido entre a moldagem e a reciclagem do concreto nas propriedades dos agregados e concretos. Os resultados indicam que resíduos reciclados logo após sua geração, contribuem positivamente para as propriedades mecânicas do concreto, devido à existência de grande quantidade de partículas não-hidratadas de cimento, tais concretos obtiveram resultados superiores para a resistência à compressão e tração quando comparados aos concretos com agregados naturais. / The concrete residues show a large potential to be recycled when compared with other residues; however, the number of studies in Brazil is very small hindering the use of this material in structural dosage. By virtue of that, it was developed a theoretical-experimental study to characterize some properties of aggregate and recycled concrete; in the theoretical study it was explored aspects related to the generation, deposition, processes for recovery, crushing, practical cases, researches involving recycled of concrete and the existent normative recommendations. In the experimental development, it was analyzed the influence of the period elapsed between the molding and the recycling of the concrete in the properties of the aggregates and concretes. The results indicate that residues recycled soon after generation, these contribute positively to the mechanical properties of the concrete due to the existence of large amount of nonhydrated cement particles, such concretes obtained results superiors for the compression strenght and tensile strenght when compared to the concretes with natural aggregates.
34

Consumer preferences for graphic, structural, and information elements on recycled paper-based package : Gender, age, and education differences

Čabajová, Andrea, Košík, Jakub January 2022 (has links)
Objective: Nowadays, the increasing pressure pushes companies to behave more environmentally friendly. Indeed, packaging made from recycled fibres can represent an essential advantage for firms in the packaging industry if it is designed in a way that appeals to consumers. The purpose of this thesis is to examine the graphic, structural and informative packaging elements and their effect on consumers’ preferences. Methodology/approach: Purposefully modified packaging designs were sent to the respondents via an online questionnaire using convenience sampling. The research analyses Slovak consumers due to their below-average environmental performance index (EPI) within the Europe. Out of 529 questionnaires collected, 483 responses were further examined and analysed by the chi-square test in SPSS. Findings: Our findings suggest that typography, colour contrast, pattern, image, shape and recyclability claims influence the preference of Slovak consumers. On the other hand, consumers did not prefer a particular layout and certificate. Furthermore, gender and age played a substantial role in the chosen recycled paper-based package, while education did not affect consumers preference in Slovakia. Practical implications: This work provides more in-depth knowledge of specific consumer preferences of packaging elements across different demographic groups, representing a valuable framework for companies’ marketing strategies. Moreover, it can serve as an inspiration for graphic designers for more innovative sustainable packaging solutions. Originality/value: Drawing upon previous research, it is evident that specific solutions for recycled paper-based packaging are lacking. This research provides new knowledge about consumer preferences for individual packaging elements. Thus, it is not only a contribution to the businesses but also a contribution to more sustainable consumption in accordance with Agenda 2030 policies.
35

Experimental investigations on the structural behaviour of reinforced geopolymer beams produced from recycled construction materials

Akduman, S., Kocaer, O., Aldemir, A., Sahmaran, M., Yildirim, Gurkan, Almahmood, Hanady A.A., Ashour, Ashraf 25 October 2022 (has links)
Yes / Concrete requires a vast amount of aggregate and cement production. Although there are some efforts in the literature to reduce the amount of Portland cement in the concrete mixture to lessen the greenhouse gas release, a limited number of studies were conducted to investigate the possibility of using this geopolymer mixtures to serve as a structural component. Therefore, this study firstly aimed to produce geopolymer concrete from construction and demolition waste-based precursors, including masonry units (red clay brick, roof tile, hollow brick, etc.) and glass. In addition, recycled aggregates produced from the concrete waste portion of the CDW were used to obtain 100% recycled construction material on the scale of the binder and aggregate phase. Then, this study investigated the possible use of this proposed geopolymer concrete to produce structural components that perform similar to conventional concrete. Therefore, the structural properties of reinforced geopolymer concrete beams produced from the recycled construction demolition wastes were evaluated in this study by conducting laboratory experiments. To this end, bending tests were performed on reinforced conventional concrete beam specimens and reinforced geopolymer concrete beam specimens. The test observations clearly showed that construction demolition waste could be recycled to produce new constructional components, considering its advantage of promoted sustainability. / The authors gratefully acknowledge the European Union’s Horizon 2020 Research and Innovation Programme’s financial assistance under Grant Agreement No: 869336 and Acronym: ICEBERG and the financial assistance of the Scientific and Technical Research Council (TUBITAK) of Turkey and the British Council under Grant no:218M102. This work was also supported by Newton Prize 2020.
36

Jean Jems: Simple Sewing Projects made by recycling old blue jeans

Tessman, Darcy 08 1900 (has links)
14 pp. / "Jean Jems" is a simple sewing project guide for 4-H youth. All projects utilized recycled blue jeans to allow youth to learn sewing skills on inexpensive fabric. Projects advance from very simple to more involved.
37

Strength and Modulus of Recycled Aggregate Concrete Subjected to Wetting and Drying Cycles

Unknown Date (has links)
The reuse of crushed aggregates for producing structural concrete is a major concern especially when it comes to its strength and durability. This study evaluated recycled aggregate concrete (RAC) for its strength and durability under simulated environmental degradation in the form of wetting-drying (W-D) cycles. The study consisted of two phases, each involving the determination of the compressive strength and modulus of elasticity using the conventional method and also a nondestructive ultrasonic pulse velocity method (Pundit Lab). Phase 1 involved 7-day curing followed by 30 W-D cycles, while Phase 2 included 28-day cured samples subjected to 15 W-D cycles. It was found that RAC specimens subjected to W-D cycles had minimal degradation in strength, making the use of RAC in construction very promising. Results from Pundit Lab compared reasonably well with conventional test results, showing promise as a nondestructive tool for the evaluation of RAC properties. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection
38

Effects of Repeated Wet-Dry Cycles on Compressive Strength of Fly-Ash Based Recycled Aggregate Geopolymer Concrete (RAGC)

Unknown Date (has links)
Geopolymer concrete (GC) is a sustainable construction material and a great alternative to regular concrete. GC is a zero-cement material made from a combination of aluminate, silicate and an activator to produce a binder-like substance. This investigation focused on the effects of wet and dry cycles on the strength and durability of fly ash-based recycled aggregate geopolymer concrete (RAGC). The wet-dry cycles were performed approximately according to ASTM D559 standards. RAGC specimens with nearly 70% recycled materials (recycled aggregate and fly ash) achieved a compressive strength of approximately 3600 psi, after 7 days of heat curing at 60ºC. Although the recycled aggregate is prone to high water absorption, the compressive strength decreased by only 4% after exposure to 21 wet-dry cycles, compared to control specimens that were not exposed to the same conditions. Accordingly, the RAGC material developed in this study can be considered as a promising environmentally friendly alternative to cement-based regular concrete. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection
39

Fractionation of recycled asphalt pavement materials: improvement of volumetric mix design driteria for High-RAP content surface mixtures

Shannon, Cory Patrick 01 July 2012 (has links)
The objective of this research is to examine the effects that different methods of RAP stockpile fractionation have on the volumetric mix design properties for high-RAP content surface mixes, with the goal of meeting all specified criteria for standard HMA mix designs. The processing of RAP materials results in the degradation of the aggregate structure of the original pavement. The increased presence of fine RAP materials in the stockpile can be attributed to the amount of crushing done on the RAP millings. Fractionation methods were designed to separate the stockpile at certain sizes to isolate the fine RAP materials which contained higher amounts of fine aggregate and negatively impacted the volumetric properties of the mix design. These isolated RAP materials were used in reduced proportions or completely eliminated, thereby decreasing the amount of fine aggregate material introduced to the mix. Mix designs were created using RAP materials included from each original stockpile and the two fractionated stockpiles created from each original stockpile at high-RAP contents of 30%, 40% and 50% by virgin binder replacement. Fractionation of RAP materials was effective in improving the volumetric properties of high-RAP content mixtures through reduction of fine aggregate material introduced by the RAP materials.
40

Determining What Factors Affect Peoples' Perceptions of the Use of Reclaimed Water as a Source for Potable Water: A Study within Hillsborough County, Florida

Alvarado Tricoche, Susana Rebecca 07 July 2014 (has links)
In response to water supply depletion challenges, countries such as Australia, the United States, and Namibia have implemented technologies that treat wastewater up to the standards permissible to use for irrigation, toilet flushing, and even drinking water. However, many of these countries have been unable to successfully implement some of their ambitious reclaimed water reuse projects due to negative public perceptions of recycling wastewater. The focus of this study was to understand which factors in risk perception theory are the most influential in shaping community perceptions of reclaimed water reuse as a future source of drinking water within Hillsborough County. The research design was comprised of a mixed methodology approach (quantitative and qualitative analyses). The methods for assessing how each of the five main factors played a role in shaping risk perception in each of the communities was comprised of three main analyses, including spatial, statistical (through multiple regression modelling in R), and personal interview data (an HOA leader, one key informant, and a focus group). Residents (n=417) from various neighborhoods were interviewed through surveys which will evaluate factors found in literature that have been shown to have the most effect in shaping risk perception theory.

Page generated in 0.0462 seconds