Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
9 chapter one research roadmap The best method of increasing the beneficial use of byproducts in highway applications is to focus on local and regional uses, because byproduct use will be highly dependent on the near-source parameters such as local competition with natural materials suppliers, transportation costs, byproduct availability, product production facilities (e.g., concrete and HMA plants), quantities available for use, regional environmental condi- tions, and traffic volumes. The general concept for matching byproducts with applications for beneficial use with optimal application use was demonstrated in a research document by Petavratzi and Barton (2006). This concept addresses the collection of the information needed as noted in the pre- ceding gaps and barriers sections. Byproduct producers and byproduct users are to develop and assemble information prior to joint producerâuser collaboration on the most beneficial byproduct usages. Byproduct producer Byproduct generator information is needed to describe, as best possible, the specific type of a given category of byproduct used in previously constructed or to-be constructed projects. At a minimum, the location of the point source(s) of byproducts within the process generating the byproduct (e.g., bottom ash and pollution control system), the technology used to gen- erate the byproduct (e.g., precaliner kiln, wet cement kiln, and dry cement kiln), quantities of each type of byproduct, stockpiling practices, geographical location of byproduct sources, and current disposal costs (e.g., tipping fees and on-site landfill containment facilities), and identification of any environmental regulations that apply to the classification and reuse of the byproduct is necessary. Some industries have undertaken byproduct risk assessment testing programs that will likely contain chemical properties of the byproducts associated with environmental impacts. These data may be useful, if available, in the development of anticipated chemical variability of the byproducts by region of the country and process technology as well as material safety data sheets. Data for the mechanical and physical prop- erties of these sources are needed so that byproduct material specifications for highway applications can be developed. The current methods for byproduct disposal, stockpiling, and any post-processing of the byproducts need to be iden- tified. At this point, an assessment of individual plant post- processing or the establishment of regional recycling centers for byproduct usage should be considered. Byproduct user Agencies assemble material physical and chemical properties that are to be evaluated for each potential use of byproducts, which was described by Petavratzi and Barton (2006) as âfitness for useâ characteristics. Both agencies and contrac- tors are to identify any environmental regulations that apply to the classification and reuse of byproducts in a particular application. The Recycled Materials Resource Center website (RMRC 2010) provides a list of test methods used to assess a wide range of highway application products. This website includes general information on values primarily associated with testing historically used natural materials. These test methods need to be more closely evaluated so that nontraditional properties are accurately reflected in the test results (e.g., optimum drying times and temperatures). The fiscal tipping point for using a given type of byproduct in a specific application product is to be estimated. For exam- ple, a byproduct to be used as a portland cement substitute at a given percent by weight for a specific number of cubic yards of concrete required each year needs to be calculated then compared with the locally available supply so that the capital cost for an additional material storage silo can be estimated. The impact of requested production changes on agency and contractor sampling, testing, and training also would be con- sidered. Information on the cost and availability of currently used raw materials is to be collected so that the impact of sub- stituting or adding recycled materials can be assessed. Potential concerns with the cost of recycling could be estimated. matching Byproduct producer with Byproduct user A match between each type of byproduct and each specific highway application is essential. Agencies require guidance for identifying enhanced performance possibilities that can be obtained from using byproducts in their projects. It is impor- tant that the guidance consider the various types of byproducts that may be provided by the byproduct supplier. Currently,
10 the most well-defined type of byproduct is fly ash, which has specifications for Type C and Type F. However, each byproduct type yields application products with differences in the performance of individual applications. That is, the type of fly ash has different impacts on PCC versus stabilized base performance characteristics. Any regulations governing the byproducts must be addressed by both the byproduct pro- ducer and the user so that the most beneficial and economical paring can be achieved. Another example of the necessity for guidance when using a byproduct is the use of steel slag in HMA applications. Several agencies reported using steel slag in surface treatments to improve pavement friction, while one state used steel slag to construct an entire lift of HMA pavement with numerous construction problems and poor performance results. The states using the byproduct for a surface treatment noted excellent results, whereas the agency placing the full lift of steel slag HMA reported major problems with density achieved during construction, durability of the in-service pavement, and the cost of recycling. Specific specifications could be developed for byproduct properties as well as their use in specific appli- cations. Performance data of these applications need to be documented. Test methods require careful selection and review for byproduct material properties, mix designs, application char- acterization for performance (e.g., compressive strength), and construction QC/QA testing such as density measurements. Test methods for the byproduct material property testing need to be assessed for ruggedness. For example, ASTM E1169-07 Standard Practice for Conducting Ruggedness Tests can be used to identify any test method preparation or procedure factors that require adjustment when testing byproducts. It is likely that sample sizes, drying times, reagents, and the number of measurements needed per lot will require adjustment. The precision of the test methods form the basis for allowable material QC/QA specification limits, which may warrant adjustment when using recycled materials. Two components are to be considered when fully assess- ing the cost of using byproducts in highway applications: eco- nomical impact(s) and environmental impact(s). The financial life-cycle cost inputs require information on the cost of raw materials, application, production, transportation, placement, testing, expected life of the application product, and salvage values and costs associated with using the different types of byproducts. The performance and salvage values and costs will be the most difficult to collect and/or estimate. The environmental evaluation requires energy and emis- sions data for each type of byproduct, application usage, product placement, and potential recycling process. Informa- tion is needed for particulate emission, gaseous emissions, energy, and heat. The assessment of the environmental impacts depends on the characteristics of a particular geographical area that is to be defined for each analysis. A standard level of evaluation should be established for consistency in reported information. Education and training are to be addressed at this point. Both byproduct producers and users must engage in technology transfer; field and lab technicians are to introduce any required testing changes or additions. Public awareness programs are essential to improve environmental stewardship perceptions of agency practices and policies.
