This project recommended changes to the cement specifications and test protocols contained in AASHTO Standard Specifications for Transportation Materials and Methods of Sampling and Testing (AASHTO M 85). These changes pertain to the amount of processing additions that can be incorporated in the cement and the tests required for evaluating acceptability of cements incorporating processing additions. The project also presented a recommended specification for evaluating processing additions that may be used in amounts exceeding those stipulated in the cement specification.
"Processing additions," such as granulated blast furnace slag, limestone, and fly ash, are interground with clinker in the manufacture of some portland cements to improve the efficiency of the manufacturing process. These additions also may improve product quality, reduce carbon dioxide emissions and energy requirements during the cement manufacturing process, and provide other economic and environmental benefits. However, there has been considerable debate recently about the effects of such additions on cement and concrete properties and on the performance and durability of the highway pavements and structures in which these materials are used. In addition, current cement specifications do not address, in a consistent manner, the use of such additions in cement manufacturing. Also, only limited research has dealt with the effects of incorporating inorganic processing additions, and there are no clear conclusions concerning the effects of using processing additions in the manufacturing process on the performance and durability of highway pavements and structures. Therefore, research is needed to assess these effects, to develop recommendations to help improve cement specifications and test protocols with regard to the use of such processing additions, and to develop guidance on the use of these cements in highway concrete.
Research included a review of the specifications and test methods currently used for evaluating portland cement and an investigation their suitability for evaluating cements incorporating processing additions. The investigation included an extensive laboratory testing program that covered the types and ranges of processing additions currently used or expected to be used in the future in the United States; considered the chemical, physical, and mineralogical characteristics of cement; and evaluated the properties of a large number of paste, mortar, and concrete specimens incorporating different types and amounts of processing additions. Based on analysis of test results, the research recommended changes to AASHTO M 85, Standard Specification for Portland Cement (included as Attachment A), that provides guidance on the testing and acceptance of portland cement incorporating maximum amounts of processing addition. The research also recommended a Standard Specification for Mineral Processing Additions for Use in the Manufacturing of Hydraulic Cements (included as Attachment B), to evaluate acceptability of processing additions when used in amounts exceeding those stipulated in the modified AASHTO M 85. NCHRP Report 607: Specifications and Protocols for Acceptance Tests on Processing Additions in Cement Manufacturing documents the work performed under this project; copies have been distributed to Program sponsors (i.e., state departments of transportation). Appendices A through F of NCHRP Report 609, which provide detailed information on material characterization, experiment design, and data analysis are available online here.