Evaluation of Low-quality Recycled Concrete Pavement Aggregates for Subgrade Soil Stabilization PDF Download
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Author: Masoumeh Tavakol
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Recycled concrete aggregate (RCA) is the byproduct of the demolition of concrete structures and pavements. An estimated 140 million tons of concrete waste is produced annually in the United States, most of which ends up in landfills. The use of RCA to replace quarried aggregates in paving projects is one way to utilize these materials and alleviate concerns regarding this increasing waste stream. RCA usage prevents waste concrete disposal into landfills, resulting in more sustainable use of mineral aggregate sources, and may further reduce costs associated with paving projects. However, the inferior physical properties of RCA, such as the presence of recycled mortar, complicate the incorporation of RCA into new concrete mixtures. State highway agencies such as the Kansas Department of Transportation are facing further issues with RCA from D-cracked pavements, raising the question if D-cracked aggregates should be used in paving operations. No known work has evaluated the effect of RCA from D-cracked pavements in subgrade soil stabilization. This study stabilized a low-plasticity clay in Kansas using RCA and three stabilizing materials (lime, Class C fly ash, and a combination of Portland cement and fly ash). Candidate mixtures with varying proportions of chemical stabilizers and D-cracked aggregates were evaluated using the standard Proctor, unconfined compressive strength, linear shrinkage, and California Bearing Ratio tests. Microstructure characteristics of selected mixtures were explored using scanning electron microscopy (SEM) and energy dispersive X-ray tests. Laboratory test results indicated that RCA, in conjunction with all cementitious materials except lime, improved clay strength, stiffness, and shrinkage properties. SEM results indicated that RCA caused a low void space and a dense arrangement of soil particles. RCA effectively improved evaluated mixture properties when an adequate soil-RCA bond was reached using chemical agents. The long-term performance of full-depth flexible pavements with stabilized mixtures as subgrade was assessed in the AASHTOWare Pavement ME Design (commonly known as MEPDG) software. The life-cycle cost of flexible pavements with stabilized mixtures was estimated for a 40-year design period. Economic analysis results indicated that RCA was cost effective only if it was used with a combination of fly ash and Portland cement.
Author: Masoumeh Tavakol
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Recycled concrete aggregate (RCA) is the byproduct of the demolition of concrete structures and pavements. An estimated 140 million tons of concrete waste is produced annually in the United States, most of which ends up in landfills. The use of RCA to replace quarried aggregates in paving projects is one way to utilize these materials and alleviate concerns regarding this increasing waste stream. RCA usage prevents waste concrete disposal into landfills, resulting in more sustainable use of mineral aggregate sources, and may further reduce costs associated with paving projects. However, the inferior physical properties of RCA, such as the presence of recycled mortar, complicate the incorporation of RCA into new concrete mixtures. State highway agencies such as the Kansas Department of Transportation are facing further issues with RCA from D-cracked pavements, raising the question if D-cracked aggregates should be used in paving operations. No known work has evaluated the effect of RCA from D-cracked pavements in subgrade soil stabilization. This study stabilized a low-plasticity clay in Kansas using RCA and three stabilizing materials (lime, Class C fly ash, and a combination of Portland cement and fly ash). Candidate mixtures with varying proportions of chemical stabilizers and D-cracked aggregates were evaluated using the standard Proctor, unconfined compressive strength, linear shrinkage, and California Bearing Ratio tests. Microstructure characteristics of selected mixtures were explored using scanning electron microscopy (SEM) and energy dispersive X-ray tests. Laboratory test results indicated that RCA, in conjunction with all cementitious materials except lime, improved clay strength, stiffness, and shrinkage properties. SEM results indicated that RCA caused a low void space and a dense arrangement of soil particles. RCA effectively improved evaluated mixture properties when an adequate soil-RCA bond was reached using chemical agents. The long-term performance of full-depth flexible pavements with stabilized mixtures as subgrade was assessed in the AASHTOWare Pavement ME Design (commonly known as MEPDG) software. The life-cycle cost of flexible pavements with stabilized mixtures was estimated for a 40-year design period. Economic analysis results indicated that RCA was cost effective only if it was used with a combination of fly ash and Portland cement.
Author:
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ISBN:
Category : Pavements, Concrete
Languages : en
Pages : 107
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Author: Daniel Gilbert Mjelde
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Category :
Languages : en
Pages :
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Author: Joakim G. Laguros
Publisher:
ISBN:
Category : Dinosaurs
Languages : en
Pages : 88
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This synthesis will be of interest to state department of transportation (DOT) construction, geotechnical, materials, and pavement system design engineers, engineering geologists, and research engineers, and others concerned with the constructibility of new pavements over existing subgrades. The synthesis describes current practice for the stabilization of existing subgrades to improve constructibility during interstate pavement reconstruction. It presents information regarding the methods available to evaluate and improve subgrade conditions for the purpose of meeting the constructibility requirements of a reconstruction project. This report of the Transportation Research Board presents data obtained from a review of the literature and a survey of the state DOTs. The synthesis reports on: subgrade evaluation methods including sampling, laboratory, and in-situ test methods, as well as assessment of existing drainage systems; constructibility factors such as existing and proposed pavement types, available equipment, and cost effectiveness of various subgrade stabilization techniques; methods of subgrade improvement including mechanical and chemical stabilization, use of recycled and waste materials, the use of geosynthetics in reinforcement and drainage applications; and construction methods with an emphasis on innovative approaches such as novel sequencing of construction traffic, use of lightweight equipment, and robotics. In addition, several case histories describing applicable pavement reconstruction projects are presented. Finally, suggestions to possibly improve the practice and the identification of research needs are also presented.
Author: Christopher Charles Pankey
Publisher:
ISBN:
Category :
Languages : en
Pages : 134
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Author: Farhad Reza
Publisher:
ISBN:
Category : Aggregates (Building materials)
Languages : en
Pages : 195
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Book Description
The need to consider sustainability in design dictates that materials should be recycled and reused whenever possible. The Minnesota Department of Transportation (MnDOT) is quite progressive in allowing the use of recycled aggregates in new construction. While the use of recycled concrete aggregate (RCA) in the base course of new pavements is quite common in Minnesota and many other states, it is rarely used in the concrete pavement itself. In fact, Minnesota was one of the few states to build multiple trial projects and has one of the largest number of concrete pavements constructed using the RCA in the concrete itself. The performance of those pavements, most of which are still in service, has never been formally evaluated against similar conventional concrete pavements. This prompted the current research study. Additional objectives were to assess the current state of practice across the nation, conduct experimental investigations using RCA in concrete, assess the sustainability and in particular the economics of using RCA in concrete, and finally to provide some recommendations for guidelines on using RCA in concrete. It has been shown by the authors and other researchers that it is possible to create strong and durable concrete mixtures using RCA as coarse aggregate in volume replacement levels of natural coarse aggregate up to 100%.
Author:
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Category : Highway engineering
Languages : en
Pages : 281
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Book Description
Due to rising costs of good quality acceptable materials for remove/replace options and traditional subgrade stabilization materials, MDOT is in need to identify potential recycled materials to treat unacceptable subgrade soils. Use of recycled materials may not only provide less costly alternatives for subgrade stabilization, their use may also alleviate landfill disposal challenges. This research study is aimed at identifying short-term and long-term advantages and disadvantages associated with subgrade stabilization using recycled materials such as Cement Kiln Dust (CKD), Lime Kiln Dust (LKD), flyash, concrete fines and mixtures of LKD and FA. An extensive laboratory testing program was conducted to determine suitability of the above recycled stabilizers for subgrade stabilization for common problematic soils found in Michigan. The laboratory investigative program involved determining the basic soil properties, developing mix designs to select proper stabilizer percentage for each soil type, CBR testing to determine pavement design parameters, and laboratory freeze/thaw testing to determine durability of stabilized subgrade sections. A limited field investigation was performed to assess insitu performance of stabilized subgrades. Based on the findings of both investigations, stabilizers were selected for long-term subgrade stabilization for different soil types and their associated pavement design inputs were determined. A design matrix with cost considerations was also developed to aid the selection of subgrade treatment options.
Author: Allen L. Cooley
Publisher:
ISBN:
Category : Pavements
Languages : en
Pages : 106
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Book Description
Based upon the work conducted in this study, it was concluded the recycled portland cement concrete pavements are available as an option for the construction of gravel cushion and aggregate base course layers.
Author: Tyson David Rupnow
Publisher:
ISBN:
Category : Cement
Languages : en
Pages : 2
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Book Description
INTRODUCTION: Many entities currently use recycled asphalt pavement (RAP) and other aggregates as base materials, temporary haul roads, and, in the case of RAP, hot mix asphalt construction. Several states currently allow the use of RAP combined with cement for a stabilized base course under both asphalt and concrete pavements. Currently, there is disagreement on what properties are required and how to test the cement and fly ash treated RAP for both asphalt and concrete pavement structures. This project investigated cement and fly ash treated RAP and other materials to determine their suitability for base course construction. OBJECTIVE: The objective of this research was to determine feasibility of cement and fly ash treated RAP and other aggregates as a structural layer for both portland cement concrete and hot mix asphalt pavement systems.
Author: James Trevor Smith
Publisher:
ISBN:
Category :
Languages : en
Pages : 206
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Book Description
Virgin aggregate is being used faster than it is being made available creating a foreseeable shortage in the future. Despite this trend, the availability of demolished concrete for use as recycled concrete aggregate (RCA) is increasing. Using this waste concrete as RCA conserves virgin aggregate, reduces the impact on landfills, decreases energy consumption and can provide cost savings. However, there are still many unanswered questions on the beneficial use of RCA in concrete pavements. This research addresses the many technical and cost-effective concerns regarding the use of RCA in concrete pavements by identifying concrete mixture and proportioning designs suitable for jointed plain concrete pavements; constructing test sections using varying amounts of RCA; monitoring performance through testing, condition surveys and sensor data; modeling RCA pavement performance; and predicting life cycle costs. The research was carried out as a partnership between the Centre for Pavement and Transportation Technology (CPATT) at the University of Waterloo, the Cement Association of Canada, Dufferin Construction, and the Natural Sciences and Engineering Research Council of Canada.rgin aggregate increase as the sources becomes depleted. Multivariable sensitivity analysis showed that the LCCA results were sensitive to construction costs, discount rate, and maintenance and rehabilitation quantities.
