Characterization of Recycled Concrete Aggregates (RCA) from an Old Foundation Structure for Road Pavement Works PDF Download

Author: Moses Akentuna
Publisher:
ISBN:
Category :
Languages : en
Pages : 208

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Book Description
The use of recycled concrete aggregates in Portland cement concrete and granular road base or sub-base works has increased steadily all over the world in order to conserve the limited natural aggregate deposits. The recycling of the demolished concrete aggregate for the use in concrete or granular pavement works will not only help to protect the environment but also an economical benefit to the user. The main drawback for the bulk utilization of demolished or recycled aggregate is its characterization and proper quality control during its production. The overall objective of this research was to characterize recycled concrete aggregates (RCA) obtained from a demolished foundation structure and to determine its suitability for Portland Cement Concrete (PCC) works and use as a granular road base or sub-base material. Tests were carried out on RCA samples to determine whether it meets the specification for concrete aggregate material or a granular road base and sub-base materials. Several concrete mixes consisting of 10, 20, 30, 40, 60, and 80 % replacement of natural coarse aggregates (NCA) with RCA were prepared and tested for compressive strength after curing periods of 7, 14, and 28 days. The compressive strength of concrete made with various percentages of RCA decreased with increasing RCA content but it increased with curing period for all concrete mixes. The durability parameters of the natural aggregates and RCA samples were investigated by using sulfate soundness, rapid freeze-thaw and micro-deval tests to ascertain their chemical and abrasive resistance. The California Bearing Ratio (CBR) of RCA base was also compared with that of a natural road base material to determine its suitability for road base or sub-base works. In this study, the flakiness and elongation indices of the RCA were found to be better than that of conventional natural aggregates. The RCA base material had lower maximum dry density, higher optimum moisture content, and low California Bearing Ratio (CBR) value compared to the natural crushed rock base (NCRB) material but was found to be a relatively good road base material.

Author: M. Chakradhara Rao
Publisher: Springer
ISBN: 9811066868
Category : Technology & Engineering
Languages : en
Pages : 349

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Book Description
This book focuses on the utilisation of construction waste material as coarse aggregate in making concrete. It discusses in detail the behaviour of recycled aggregate under impact load along with other structural applications, and explains the various quality-improvement techniques for recycled aggregate and recycled aggregate concrete (RAC). The first chapter describes the importance of recycling construction and demolition waste and the status quo of global construction and demolition waste recycling. The second chapter examines the recycled aggregate production methodology. Subsequent chapters address the physical and mechanical characteristics and different research findings, as well as the engineering properties of recycled aggregate concrete. Further, the interrelationships among the mechanical properties of recycled aggregate concrete are discussed. The book also explores long-term properties like shrinkage and creep, durability properties, and microstructural characterisation. It will serve as a valuable resource for researchers and professionals alike.

Author: Marco Pepe
Publisher: Springer
ISBN: 3319264737
Category : Technology & Engineering
Languages : en
Pages : 178

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Book Description
This book reports on the physical and mechanical characterization of Recycled Aggregate Concrete (RAC), produced through a partial-to-total replacement of ordinary aggregates with what have been dubbed Recycled Concrete Aggregates (RCAs). It proposes a theoretical framework for understanding the relationships between RCAs and RCA, and for predicting the resulting behavior of RAC. The book demonstrates that in the case of RAC two additional parameters have to be taken into account than with ordinary aggregates, due to the composite nature and higher porosity of RCAs. By extending Abrams’ Law for Recycled Aggregate Concrete, it represents a first step in the formulation of a general model for predicting the properties of RAC. The theoretical approach presented here addresses an important gap in the literature and is expected to stimulate new research on the use of this more sustainable form of concrete in structural applications.

Author: Bora Cetin
Publisher:
ISBN:
Category : Aggregates (Building materials)
Languages : en
Pages : 154

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Book Description
The use of recycled materials promotes sustainability in roadway construction by reducing the consumption of energy and emission of greenhouse gases associated with mining and the production of virgin aggregate (VA). Recycled asphalt pavement (RAP) and recycled concrete aggregate (RCA) have comparable characteristics to VA that have been used in roadway base course applications. This study develops a database for RAP and RCA material characteristics, including gradation, compaction, resilient modulus (Mr), California bearing ratio (CBR), and saturated hydraulic conductivity (Ksat). In addition, this study summarizes construction specifications provided by several departments of transportation (DOTs) regarding the use of recycled aggregates in pavement systems. The effects of the presence of RAP and RCA in aggregate matrices on the engineering and index properties of aggregates are investigated and some trends are observed. For example, the study finds a higher RAP content reveals a higher summary Mr (SMr), and a higher RCA content causes an increase in optimum moisture content (OMC) and a decrease in maximum dry unit weight (MDU). In addition, a series of AASHTOWare Pavement Mechanistic-Empirical (ME) Design (PMED) analyses are conducted for three traffic volumes [low (1,000 AADTT), medium (7,500 AADTT), and high (25,000 AADTT)] with the material inputs collected for the database to determine whether different values of different characteristics of RCA and RAP can be used in flexible/rigid pavement designs. Results show that Mr has a higher effect on pavement distress predictions compared to gradation and saturated hydraulic conductivity (Ksat).

Author: Jianzhuang Xiao
Publisher: Springer
ISBN: 366253987X
Category : Technology & Engineering
Languages : en
Pages : 670

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Book Description
This book describes how, given the global challenge of a shortage of natural resources in the 21st century, the recycling of waste concrete is one of the most important means of implementing sustainable construction development strategies. Firstly, the book presents key findings on the micro- and meso-structure of recycled aggregate concrete (RAC), while the second part focuses on the mechanical properties of RAC: the strength, elastic modulus, Poisson’s ratio, stress-strain curve, etc. The third part of the book explores research on the durability of RAC: carbonization, chloride penetration, shrinkage and creep. It then presents key information on the mechanical behavior and seismic performance of RAC elements and structures: beams, columns, slabs, beam-column joints, and frames. Lastly, the book puts forward design guidelines for recycled aggregate concrete structures. Taken as a whole, the research results – based on a series of investigations the author has condu cted on the mechanical properties, durability and structural performance of recycled aggregate concrete (RAC) over the past 10 years – demonstrate that, with proper design and construction, it is safe and feasible to utilize RAC structures in civil engineering applications. The book will greatly benefit researchers, postgraduates, and engineers in civil engineering with an interest in this field.

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.

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: American Concrete Pavement Association
Publisher:
ISBN: 9780980025118
Category : Pavements, Concrete
Languages : en
Pages : 84

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Book Description
This publication provides numerous recommendations concerning RCA [recycled concrete aggregate] production and use (including both foundation applications and use in new concrete mixtures), as well as guide specifications to assist users in developing successful RCA construction projects.

Author: Ravindra K Dhir
Publisher: ICE Publishing
ISBN: 9780727764638
Category : Technology & Engineering
Languages : en
Pages : 0

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Book Description
The book is an ideal source of information on the subject and would be a suitable addition to any library as a resource for researchers seeking to develop an overview of the research on this topic.

Author: Pralendra Singh
Publisher:
ISBN:
Category : Aggregates (Building materials)
Languages : en
Pages : 0

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Book Description
The sources of natural or virgin coarse aggregates are diminishing in alarming rate and its production is quite expensive, uses a lot of energy, and is not environmental friendly. Hence, utilizing the recycled aggregates like reclaimed or recycled concrete aggregate (RCA) and recycled asphalt pavement (RAP) on road pavement will not only preserve the natural aggregates but also reduce the negative environmental impact. It also helps to conserve the waste landfill sites. The major downside for the use of the recycled aggregate is the quality control during its production. This research characterizes RCA samples obtained from a demolished old foundation and RAP samples from old parking lot and determines their suitability as road pavement materials. Virgin aggregates, recycled aggregates, and several blended mixtures with 20 to 80% replacement of natural coarse aggregate or virgin aggregate (NCA or VA) by weight with RCA and RAP were prepared and tested for resilient modulus (M r) and California Bearing Ratio (CBR) test. The durability of the virgin aggregate and recycled aggregate were also determined by micro-deval test. The resilient modulus value of 100% RCA and 100% VA was found to be very similar or higher but for 100% RAP the resilient modulus is higher than that of the 100%VA. The Resilient modulus of the RAP blended mixtures increases with the increase in the content of RAP percentage and for the RCA it was not consistent. The CBR values for the blended mixtures decreases with the increase in the percentage of the recycled aggregates. The micro-deval degradation test result for RCA was more than of VA due to presence adhere materials in RCA.