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Author: Majella Anson-Cartwright Publisher: ISBN: 9780494764121 Category : Languages : en Pages : 574
Book Description
By optimizing the packing of the combined aggregate gradations, the cement paste content needed to make concrete can be reduced, improving sustainability, cost, performance, durability, and workability. Optimization can be achieved using theoretical and empirical techniques, or waste concrete material as an intermediate size fraction. However, the potential for improvement is currently limited by prescriptive grading specifications that require meeting individual requirements for fine and coarse aggregates.From this study, using various optimization techniques, it was found that by inclusion of an intermediate sized aggregate material, a reduction in cement paste up to 16% is possible for 35 MPa and 50 MPa mix designs typically used in Ontario bridge decks. The aggregate materials used were a natural sand, and two crushed limestones of 19.0 mm and 6.7 mm maximum size. From these findings, recommendations are made for improving the current Ontario Provincial Standard Specification (OPSS) 1002 used for concrete aggregates.
Author: Majella Anson-Cartwright Publisher: ISBN: 9780494764121 Category : Languages : en Pages : 574
Book Description
By optimizing the packing of the combined aggregate gradations, the cement paste content needed to make concrete can be reduced, improving sustainability, cost, performance, durability, and workability. Optimization can be achieved using theoretical and empirical techniques, or waste concrete material as an intermediate size fraction. However, the potential for improvement is currently limited by prescriptive grading specifications that require meeting individual requirements for fine and coarse aggregates.From this study, using various optimization techniques, it was found that by inclusion of an intermediate sized aggregate material, a reduction in cement paste up to 16% is possible for 35 MPa and 50 MPa mix designs typically used in Ontario bridge decks. The aggregate materials used were a natural sand, and two crushed limestones of 19.0 mm and 6.7 mm maximum size. From these findings, recommendations are made for improving the current Ontario Provincial Standard Specification (OPSS) 1002 used for concrete aggregates.
Author: Miras Mamirov Publisher: ISBN: Category : Pavements, Concrete Languages : en Pages : 109
Book Description
The main objective of this study was to evaluate the effect of aggregate particle packing optimization and cement reduction on Nebraska slip-form pavement concrete performance. A literature review was conducted to examine different aggregate optimization tools, quality control tests, and historical data of Nebraska Department of Transportation (NDOT) mixtures. It was found that the Modified Toufar Model has good potential in optimizing particle packing and predicting packing degrees. The combined void content test was found to be useful to experimentally justify optimized aggregate gradations. Two specific pavement concrete workability tests, i.e., the Box Test and the VKelly Test, were used to evaluate the effect of cement reduction and optimized aggregate gradation on pavement concrete workability. The Box Test ranking was modified to provide a more detailed and objective evaluation. Analysis of different aggregate combinations has shown that experimental packing from the combined void content test has a high correlation with estimated packing from the Modified Toufar Model. Results showed that when the optimized aggregate gradation is used, cement content can be effectively reduced by up to 1.0 sack (94 lb/yd3) without compromising the fresh properties, mechanical properties, and permeability. Based on the results of free and restrained shrinkage, it was justified that shrinkage and cracking potential can be reduced in optimized concrete mixtures. Freeze/thaw resistance can be slightly improved with optimized mixtures. A mix design improvement procedure considering both theoretical and experimental packing and the minimum excess paste-to-aggregate ratio can be used to design concrete with an optimum cement content.The main objective of this study was to evaluate the effect of aggregate particle packing optimization and cement reduction on Nebraska slip-form pavement concrete performance. A literature review was conducted to examine different aggregate optimization tools, quality control tests, and historical data of Nebraska Department of Transportation (NDOT) mixtures. It was found that the Modified Toufar Model has good potential in optimizing particle packing and predicting packing degrees. The combined void content test was found to be useful to experimentally justify optimized aggregate gradations. Two specific pavement concrete workability tests, i.e., the Box Test and the VKelly Test, were used to evaluate the effect of cement reduction and optimized aggregate gradation on pavement concrete workability. The Box Test ranking was modified to provide a more detailed and objective evaluation. Considering one of the goals of the study was to maximize the use of local materials, locally available cementitious materials and aggregates from East and West Nebraska were selected. Analysis of different aggregate combinations has shown that experimental packing from the combined void content test has a high correlation with estimated packing from the Modified Toufar Model. Results also demonstrated that the current aggregate combination is not the optimum gradation and can be improved. The experimental program included in this study consisted of three Phases. Phase 1 focused on obtaining promising aggregate blends by maintaining the standard cement content (564 lb/yd3, 335 kg/m3). Fresh concrete properties were the main criteria to select promising blends. Phase 2 included an evaluation of performance of pavement concrete with cement content reduced by 0.5 sack (47 lb/yd3, 28 kg/m3) steps for other reference and optimized aggregate blends. Results justified that when optimum gradation is used, cement could be reduced up to 94 lb/yd3 (56 kg/m3). Phase 3 is the performance evaluation phase, which included evaluating the reference mix and selected promising mixes for setting time, modulus of elasticity, free shrinkage, restrained shrinkage, and freeze/thaw resistance. Mixtures with reduced cement and optimized aggregate gradation have shown improved freeze/thaw resistance and lower shrinkage rate. Finally, a mix design improvement procedure incorporating theoretical and experimental particle packing and using excess paste-to-aggregates ratio as the control parameter was proposed. To sum up, the study has justified that the Modified Toufar Model and the combined void content test can be useful tools in aggregate gradation optimization. In order to evaluate workability of pavement concrete more accurately, the Box Test ranking was modified based on image analysis of surface and edge quality. It was also proved that mixtures with reduced cement content and optimized aggregate gradation perform better in terms of freeze/thaw resistance and shrinkage.
Author: Imad L. Al-Qadi Publisher: CRC Press ISBN: 1351659219 Category : Technology & Engineering Languages : en Pages : 298
Book Description
An increasing number of agencies, academic institutes, and governmental and industrial bodies are embracing the principles of sustainability in managing their activities and conducting business. Pavement Life-Cycle Assessment contains contributions to the Pavement Life-Cycle Assessment Symposium 2017 (Champaign, IL, USA, 12-13 April 2017) and discusses the current status of as well as future developments for LCA implementation in project- and network-level applications. The papers cover a wide variety of topics: - Recent developments for the regional inventory databases for materials, construction, and maintenance and rehabilitation life-cycle stages and critical challenges - Review of methodological choices and impact on LCA results - Use of LCA in decision making for project selection - Implementation of case studies and lessons learned: agency perspectives - Integration of LCA into pavement management systems (PMS) - Project-level LCA implementation case studies - Network-level LCA applications and critical challenges - Use-phase rolling resistance models and field validation - Uncertainty assessment in all life-cycle stages - Role of PCR and EPDs in the implementation of LCA Pavement Life-Cycle Assessment will be of interest to academics, professionals, and policymakers involved or interested in Highway and Airport Pavements.
Author: United States. Federal Highway Administration Publisher: ISBN: Category : Aggregates (Building materials) Languages : en Pages : 4
Book Description
Historically, aggregate gradation has been controlled by specifications that call out envelopes for individual fractions, typically the coarse aggregate and the fine aggregate. The shortcoming of this approach is that the gradation of the overall system is not addressed. While it is sensible to stockpile coarse and fine fractions separately to prevent segregation, it is the combined system that is critical in the final mixture.
Author: Majella Anson-Cartwright
Author: Majella Anson-Cartwright
Author: Miras Mamirov
Author: FIB – International Federation for Structural Concrete
Author: Majella Anson-Cartwright
Author: Imad L. Al-Qadi
Author: Subhasis Pradhan
Author: David Newton Richardson
Author: Ezgi Yurdakul
Author: United States. Federal Highway Administration
Author: ACI Committee 302