Increased Use of Fly Ash in Hydraulic Cement Concrete (HCC) for Pavement Layers and Transportation Structures (original) (raw)
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High-volume Fly Ash Concrete for Pavements Findings: Volume 1
2021
High-volume fly ash concrete (HVFAC) has improved durability and sustainability properties at a lower cost than conventional concrete, but its early-age properties like strength gain, setting time, and air entrainment can present challenges for application to concrete pavements. This research report helps with the implementation of HVFAC for pavement applications by providing guidelines for HVFAC mix design, testing protocols, and new tools for better quality control of HVFAC properties. Calorimeter tests were performed to evaluate the effects of fly ash sources, cement–fly ash interactions, chemical admixtures, and limestone replacement on the setting times and hydration reaction of HVFAC. To better target the initial air-entraining agent dosage for HVFAC, a calibration curve between air-entraining dosage for achieving 6% air content and fly ash foam index test has been developed. Further, a digital foam index test was developed to make this test more consistent across different la...
Best Practices Guide for High-Volume Fly Ash Concretes : Assuring Properties and Performance
2013
A best practices guide is developed from a synthesis of recent research on high-volume fly ash (HVFA) concrete mixtures. These best practices can be applied by the concrete construction industry to achieve desired properties and to ensure the (high) performance of HVFA concrete mixtures in practice. As such, the report considers all aspects of HVFA concrete production, from the characterization of the starting materials, through mixture proportioning and curing options to achieve desired properties, to the in-place early-age and long-term performance of the concrete in its fresh and hardened states. Both mechanical and transport properties are considered in detail. Perspective is established based on a brief review of current practices being employed nationally. Each topical section is concluded with a practice-based set of recommendations for the design and construction community. The report is intended to serve as a valuable resource to these communities, providing both a research summary and a guide to practical steps that can be taken to achieve the optimum performance of these sustainable concrete mixtures.
Development and Evaluation of High-Volume Fly Ash (HVFA) Concrete Mixes
Concrete is the world’s most consumed man-made material. Unfortunately, the production of portland cement, the active ingredient in concrete, generates a significant amount of carbon dioxide. For each pound of cement produced, approximately one pound of carbon dioxide is released into the atmosphere. With cement production reaching nearly 6 billion tons per year worldwide, the sustainability of concrete is a very real concern. Since the 1930’s, fly ash – a pozzolanic material – has been used as a partial replacement of portland cement in concrete to improve the material’s strength and durability, while also limiting the amount of early heat generation. From an environmental perspective, replacing cement with fly ash reduces concrete’s overall carbon footprint and diverts an industrial by-product from the solid waste stream (currently, about 40 percent of fly ash is reclaimed for beneficial reuse and 60 percent is disposed of in landfills). Traditional specifications limit the amount...
Effects of Mixing and Transportation on Characteristics of Cementitious Systems Containing Fly Ash
According to the Portland Cement Association (PCA) (2000) over 50% of ready-mixed concrete currently contains fly ash. The use of fly ash is likely to increase because (1) the construction industry is attempting to become more sustainable; (2) fly ash can improve concrete performance; and (3) replacing cement with fly ash can reduce material costs. Fly ash-concrete systems are now becoming very common in our infrastructure systems. Many concrete specifications place limits on the mixing and transportation of concrete systems. In fact, 48 of 50 State Highway Agencies (SHAs) place time limits on concrete placements and 30 of 50 SHAs place limits on the number of truck mixer drum revolutions. Few studies have been performed to assess whether these limits are applicable to concrete systems containing fly ash. This paper presents the assessment of the influence of mixing time and number of revolutions on the characteristics of cementitious systems containing fly ash. The characterization methods evaluated in this study include the dissolution rate of hydroxyl ion, setting time, flowability, and compressive strength Results indicate that replacing cement with fly ash can reduce the negative effects on flowability and compressive strength resulting from increased mixing times and number of mixer revolutions. The limits of mixing time and number of revolutions of ready-mixed concrete from most SHAs are likely not applicable for cementitious systems containing fly ash and consideration should be given to modify these specifications.
PRODUCTION OF CONCRETE CONTAINING FLY ASH FOR STRUCTURAL APPLICATIONS
Structural applications of concrete containing fly ash have been limited mainly to high strength concrete in the past. This trend is primarily due to the lack of information available to the resident engineer concerning curing conditions, setting times, strength characteristics and durability of normal strength fly ash concrete. This study addresses some of the major concerns of resident highway engineers on concrete containing fly ash for structural concrete in highway applications. This report summarizes the experimental observations and conclusions from a research program investigating the properties of both fresh and hardened structural concrete containing fly ash. Tests were performed to establish guidelines for the selection of materials and trial mix design procedures for producing quality concrete containing fly ash. The study investigated freeze-thaw resistance, flexural and compressive strength characteristics, mixing conditions and procedures and curing conditions such as temperature, humidity, curing methods and rate of strength gain. Types A and B fly ashes were used in this study as a replacement for 0, 15, 25, and 35% Type I portland cement by weight. In addition, Type IP cement containing 20% Type A fly ash was used. The results of this study show that concrete containing fly ash can be designed and proportioned to meet present Texas SDHPT specifications for structural applications. In addition, this study reveals that an optimum mix design for concrete containing fly ash is both technically and economically advantageous to the Texas SDHPT. This report provides the resident engineer with recommendations to ensure the production of quality concrete containing fly ash for structural applications.
Field investigation of high-volume fly ash pavement concrete
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: a b s t r a c t Field investigation of high-volume fly ash (HVFA) concrete in pavement construction was carried out. Test results performed on cores drilled from pavement after 270 days of concrete age showed that use of HVFA results in production of pavement concrete with improvements in: strength; moisture barrier qualities; and abrasive resistance characteristics. These improvements are brought about by the pozzolanic reaction of fly ash with the hydrates of cement that favorably changes the microstructure and interfacial transition zone in the resulting concrete. Use of high volume of fly ash in pavement concrete as partial replacement for cement is estimated to produce major energy and environmental gains and is a practice that is aimed at producing durable and sustainable concrete-based infrastructure. The use of HVFA concrete can significantly economize the construction of concrete pavements and improve the service life of transportation infrastructure.
2010 GSW Proceedings
This paper discusses the findings of research effort about the strength of light weight concrete designed with varying fly ash levels. The topic was assigned to an undergraduate student as part of the honor thesis program of Farleigh Dickinson University, Teaneck, NJ. Concrete mixes were prepared using three different types of light weight coarse aggregates; Expanded Polystyrene Aggregate (EPA), Vermiculite and Expanded Shale Aggregate (ESA). Fly ash was introduced to the mix designs at levels of 10, 20 and 30% of total cementitious material. Expanded shale aggregate fines were also used as a substitute for conventional sand. A compressive strength testing program was conducted to determine 3, 7 and 28-day strength of each mix design. Results showed great potential and consistency for the mix designs with expanded shale and vermiculite, reaching strength to unit weight ratios higher than the conventional concrete mix design.
Class F Fly Ash Assessment for Use in Concrete Pavements
2017
The Wisconsin Department of Transportation (WisDOT) currently specifies Class C fly ash for use as a partial replacement for portland cement in concrete pavements. Class F fly ash sources were eliminated from WisDOT specifications in the 1990's due to high values of loss on ignition (LOI) which led to difficulties in establishing and maintaining a proper entrained air void system in the concrete used in paving applications. A recent study that looked at the use of Class F fly ash demonstrated its potential usage in WisDOT specifications. However, WisDOT needs more evaluation with regard to durability testing. Specifically, research is needed to evaluate the feasibility of expanding current specifications to allow for use of Class F fly ash in concrete paving applications with southern Wisconsin aggregates. In order for Class F fly ash to be a viable alternative as a supplemental cementitious material, its use must produce mixes that meet current performance standards with respect to strength (including early strength) and durability, when compared with a commonly used Class C fly ash. The main objective of this study is to evaluate whether the locally available Class F fly ash from Elm Road Generating Station, operated by WE Energies and located in Oak Creek, Wisconsin, will provide satisfactory performance in concrete pavement, in comparison with a Class C fly ash from Columbia Energy Center currently in use. The study will also provide mix design guidance related to acceptable proportions of Class F fly ash that can be used in paving applications without negatively impacting performance. The performance evaluation of optimized concrete included workability (slump), air content, compressive strength, freezethaw and salt scaling resistance in accordance with the relevant AASHTO or ASTM standards. Finally, the reported research recommended the selection of fly ash for low-slump concrete with reduced cementitious material content intended for paving applications.