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One area for sustainable engineering is the efficient use of recycled aggregates obtained from construction and demolition and also as by-products derived from industrial waste that optimises economic and environmental benefits. For the past five decades, studies on the effect of coarse recycled aggregates (RCA) on properties of concrete have been going on, and in fact, none of them reported that good quality coarse RCA, from the mechanical point of view, is unsustainable for structural use. However, according to the limits stated in BS EN 8500 part 2 (2006), at least 87% of the coarse RCA shall be obtained by crushing old hardened concrete debris. As it was impossible to obtain such good quality aggregates from existing plants, coarse recycled aggregate (RA*) containing 60% of coarse RCA, 10% asphalt, 10% brick, 15% unbound aggregate, and 5% fines and other materials was used in this study. The main aim of this study was to determine and compare the structural properties of natural aggregate concrete (NAC) and recycled aggregate concrete (RAC) of equal compressive strength by using different percentage of course RA* and to investigate the suitability of coarse RA* for use in steel-reinforced concrete elements. The study was carried out in three phases. Phase 1 involved the characterisation of the aggregates through a testing regime which include physical and mechanical assessments to study their possible application in concrete production. It was found that the aggregates were suitable to produce normal concrete. For the Phase 2, the effect of the coarse RA* content (up to 100%) on the main properties of concrete was investigated. The results showed that there was a gradual decrease in slump (up to 24%), compressive strength (up to 21%), flexural strength (up to 10%) and modulus of elasticity (up to 30%) as the percentage of coarse RA* increased up to 100%. Thereafter, NA concrete and RA concrete with the same slump and compressive strength made with 100% Portland cement (PC) only and also with a combination of 70% PC and 30% pulverised fuel ash (PFA), were produced. Flexural strength, modulus of elasticity, drying shrinkage, and creep were determined and compared. The compressive strength of RA concretes was increased by lowering the w/c ratio through reducing the free water content. For the Phase 3, pull-out test was carried out using 16mm and 20mm reformed bars embedded in concrete cylinders made with equal strength NA and RA concretes to investigate the bonding strength. It was discovered that the coarse RA* content had no significant effect on the values of pull-out force. Then, for studying flexural properties (cracking load, ultimate load, deflection, strain in rebar, strain in concrete, and pattern of cracks) of steel-reinforced recycled concrete (RRC) beams, two types of beam sections (under-reinforced and over-reinforced) were made with equal strength NA and RA concretes and tested. It was discovered that the difference in ultimate load values was negligible. Although higher deflections were observed for RA beams, the deflections were still within acceptable limits. Overall, it was concluded that, the flexural behaviour of steel-RRC beams made with equal strength concrete is not considerably affected by the presence of coarse RA*, as well as PFA, and the differences were minor with no practical significance. However, due to effect of coarse RA* on the shrinkage and creep strains, their use in structural elements prone to such deformations may require some special considerations.
The quality and testing of materials used in construction are covered by reference to the appropriate ASTM standard specifications. Welding of reinforcement is covered by reference to the appropriate AWS standard. Uses of the Code include adoption by reference in general building codes, and earlier editions have been widely used in this manner. The Code is written in a format that allows such reference without change to its language. Therefore, background details or suggestions for carrying out the requirements or intent of the Code portion cannot be included. The Commentary is provided for this purpose. Some of the considerations of the committee in developing the Code portion are discussed within the Commentary, with emphasis given to the explanation of new or revised provisions. Much of the research data referenced in preparing the Code is cited for the user desiring to study individual questions in greater detail. Other documents that provide suggestions for carrying out the requirements of the Code are also cited.
This book is the result of a Special Issue published in Applied Sciences, entitled “New Trends in Recycled Aggregate Concrete". It identifies emerging research areas within the field of recycled aggregate concrete and contributes to the increased use of this eco-efficient material. Its contents are organised in the following sections: Upscaling the use of recycled aggregate concrete in structural design; Large scale applications of recycled aggregate concrete; Long-term behaviour of recycled aggregate concrete; Performance of recycled aggregate concrete in very aggressive environments; Reliability of recycled aggregate concrete structures; Life cycle assessment of recycled aggregate concrete; New applications of recycled aggregate concrete.
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.
Concrete is the most used man-made material in the world since its invention. The widespread use of this material has led to continuous developments such as ultra-high strength concrete and self-compacting concrete. Recycled Aggregate in Concrete: Use of Industrial, Construction and Demolition Waste focuses on the recent development which the use of various types of recycled waste materials as aggregate in the production of various types of concrete. By drawing together information and data from various fields and sources, Recycled Aggregate in Concrete: Use of Industrial, Construction and Demolition Waste provides full coverage of this subject. Divided into two parts, a compilation of varied literature data related to the use of various types of industrial waste as aggregates in concrete is followed by a discussion of the use of construction and demolition waste as aggregate in concrete. The properties of the aggregates and their effect on various concrete properties are presented, and the quantitative procedure to estimate the properties of concrete containing construction and demolition waste as aggregates is explained. Current codes and practices developed in various countries to use construction and demolition waste as aggregates in concrete and issues related to the sustainability of cement and concrete production are also discussed. The comprehensive information presented in Recycled Aggregate in Concrete: Use of Industrial, Construction and Demolition Waste will be helpful to graduate students, researchers and concrete technologists. The collected data will also be an essential reference for practicing engineers who face problems concerning the use of these materials in concrete production.
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.
Sustainable Construction Materials: Recycled Aggregate focuses on the massive systematic need that is necessary to encourage the uptake of recycled and secondary materials (RSM) in the construction industry. This book is the fifth and the last of the series on sustainable construction materials and like the previous four, it is also different to the norm. Its uniqueness lies in using the newly developed, Analytical Systemisation Method, in building the data-matrix sourced from 1413 publications, contributed by 2213 authors from 965 institutions in 67 countries, from 1977 to 2018, on the subject of recycled aggregate as a construction material, and systematically analysing, evaluating and modelling this information for use of the material as an aggregate concrete and mortar, geotechnics and road pavement applications. Environmental issues, case studies and standards are also discussed. The work establishes what is already known and can be used to further progress the use of sustainable construction materials. It can also help to avoid repetitive research and save valuable resources. The book is structured in an incisive and easy to digest manner and is particularly suited for researchers, academics, design engineers, specifiers, contractors, and government bodies dealing with construction works. - Provides an exhaustive and comprehensively organized list of globally-based published literature spanning 5000 references - Offers an analysis, evaluation, repackaging and modeling of existing knowledge that encourages more responsible use of waste materials - Provides a wealth of knowledge for use in many sectors relating to the construction profession, including academia, research, practice and adoption of RSM
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.
The building explosion during the years 1945-1960 will inevitably lead to increased demolition in the next decades since the lifetime distribution of structures no longer fulfills its functional social requirements in an acceptable way. In the building period mentioned there was a great increase in reinforced and prestressed concrete construction. Consequently there is now more and more concrete to be demolished. Increasingly severe demands will be made upon demolition technology, including the demand for human- and environment-friendly techniques. On the other hand, the possibility of disposing of debris by dumping is steadily diminishing, especially close to major cities and generally in countries with a high population density. At the same time in such countries and in such urban areas a shortage of aggregates for making concrete will develop as a result of restrictions on aggregate working because of its effect on the environment and because of the unavailability of aggregate deposits due to urban development. From the foregoing it follows that recycling and re-use of environment- and human-friendly demolished and fragmented building rubble should be considered. The translation of this general problem into terms of materials science is possible by forming clear ideas of adhesion and cohesion: the whole process of demolition, fragmentation, and recycling or re-use of concrete is to break the bonding forces between atoms and molecules and to form new bonds across the interfaces of various particles of either the same nature or a different nature.