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This interim report documents the field performance of nine concrete pavement projects that incorporate recycled concrete aggregate (RCA) in the construction of the pavement. Multiple sections were evaluated on many of the nine projects, due to perceived differences in performance levels or variations in pavement design (such as the use of virgin aggregate or the inclusion of dowel bars). All told, a total of 17 sections (of which 12 contain RCA) were subjected to an extensive field testing program, consisting of pavement condition surveys, drainage surveys, falling weight deflectometer (FWD) testing, coring, and serviceability assessments.
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.
ABSTRACT: Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Engineering CONCRETE CONTAINING RECYCLED CONCRETE AGGREGATE FOR USE IN CONCRETE PAVEMENT By Patrick Amoah Bekoe August 2009 Chair: Mang Tia Major: Civil Engineering Our study evaluated the feasibility of using concrete containing recycled concrete aggregate (RCA) in concrete pavement application. Concrete containing 0%, 25% and 50% of RCA were produced in the laboratory and their properties vital to the performance of concrete pavement evaluated. Result from the laboratory testing program indicates that the compressive strength and elastic modulus is reduced slightly as the percentage of RCA increases. The flexural strength, splitting tensile strength and coefficient of thermal expansion is about the same for concrete containing virgin aggregate and RCA. The free shrinkage increases slightly as the percentage of RCA increases. From the measured properties, a finite element analysis was performed to determine how the concretes containing the different amounts of RCA would perform if they were used in a typical concrete pavement in Florida. The analysis from the finite element model determined the maximum stresses under critical temperature and load conditions. The potential performance of the different pavements was evaluated based on the computed maximum stress to the flexural strength ratio. The maximum stress to flexural strength ratio in the pavement was found to be about the same as the percentage of RCA increases. This indicates that RCA can be used successfully in concrete pavement without affecting the performance.
Few studies have focused on the effect of recycled materials on the concrete slab load capacity. This study used virgin and recycled aggregates--fractionated reclaimed asphalt pavement (FRAP) and recycled concrete aggregate (RCA)--and by-product cementitious materials--ground granulated blast furnace slag and fly ash--to cast and test the load capacity of single- and two-lift concrete slabs. Five concrete mixtures were examined, which were virgin aggregate (the control) and four different replacements of coarse aggregate: 45% FRAP, 45% FRAP with macrofibers, 100% RCA, and a blend of 45% FRAP and 55% RCA.
The main objective of this research is to evaluate the feasibility of using high-volume recycled materials for concrete production in rigid pavement. The goal was to replace 50% of the solids with recycled materials and industrial by-products. The performance of concrete mixtures made with different fine and coarse recycled concrete aggregate (RCA) contents and binder types was investigated. Both single-layer rigid pavement and two-lift concrete pavement (2LCP) were considered. The optimized mixtures developed 91-d compressive strength results from 5,900 to 8,600 psi. Flexural strength was mostly higher than 600 psi at 28 d. The modulus of elasticity ranged from 4.7 to 6.7 ksi at 56 d. Using the optimized binder incorporating 35% Class C fly ash and 15% slag reduced the 150-d drying shrinkage to values less than 350 to 500 micro epsilon. However, an increase in fine RCA content from 15% to 40% resulted in increased shrinkage values (up to 650 micro epsilon). The optimized mixtures exhibited frost durability factor higher than 88%. De-icing salt scaling ratings were limited to 3 for all mixtures, except the mixture with 15% GP and 35% FA-C. All mixtures exhibited comparable coefficient of thermal expansion (CTE) values, ranging from 4.8 to 5.2 E-6 in/in/degrees F. Incorporation of RCA did not have a significant effect on CTE values. Based on the obtained data, it was concluded that concrete mixtures incorporating high volume recycled aggregate and SCMs can present viable choices for sustainable pavement construction. The following four mixtures exhibited satisfactory performance and can be used for construction of the single layer pavement: (1) MoDOT PCCP as the reference concrete; (2) concrete incorporating the optimized binder (15% slag and 35% Class C fly ash replacements), 0.40 w/cm, without any RCA; (3) concrete incorporating the optimized binder, 0.40 w/cm, and 30% coarse RCA (30C); concrete incorporating the optimized binder, 0.37 w/cm, and 50% coarse RCA (50C-37). The following three mixtures can be incorporated for construction of the top layer of the 2LCP systems: (1) MoDOT PCCP as reference; (2) concrete incorporating the optimized binder, 0.40 w/cm, without any RCA; (3) concrete incorporating the optimized binder, 0.40 w/cm, and 30% coarse RCA (30C). The following two mixtures can be employed for construction of the bottom layer of the 2LCP systems: (1) concrete incorporating the optimized binder, 0.37 w/cm, 50% coarse RCA, and 15% fine RCA (50C15F-37); (2) concrete incorporating the optimized binder, 0.37 w/cm, and 70% coarse RCA (70C-37).
Recycled Concrete: Technologies and Performance presents the latest technologies that can be applied to produce high and consistent quality recycled aggregate for use in structural concrete, and in alternative binders like Geopolymer and other types of concrete. The book discusses the lifecycle assessment of implementing sustainable construction technologies and evaluates the environmental impacts of recycled concrete in construction applications. It covers their use in the production of durable recycled concrete, their reduced environmental impact, quality improvement techniques, and more, making it valuable and relevant for civil and structural engineers, recycle industry managers, ready-mix and precast concrete producers and researchers. - Discusses alternative binding materials for recycled aggregate - Covers how to use concrete with recycled aggregates, along with the advantages and disadvantages - Provides guidance on using recycled concrete aggregates, designing mixtures and how to best produce RCAs
Addressing the interactions between the different design and construction variables and techniques this book illustrates best practices for constructing economical, long life concrete pavements. The book proceeds in much the same way as a pavement construction project. First, different alternatives for concrete pavement solutions are outlined. The desired performance and behaviour parameters are identified. Next, appropriate materials are outlined and the most suitable concrete proportions determined. The design can be completed, and then the necessary construction steps for translating the design into a durable facility are carried out. Although the focus reflects highways as the most common application, special features of airport, industrial, and light duty pavements are also addressed. Use is made of modeling and performance tools such as HIPERPAV and LTPP to illustrate behavior and performance, along with some case studies. As concrete pavements are more complex than they seem, and the costs of mistakes or of over-design can be high, this is a valuable book for engineers in both the public and private sectors.