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1 C H A P T E R 1 Background Accurate measurements of the specific gravity and absorp- tion of coarse and fine aggregates are essential to the devel- opment of satisfactory mix designs and production of both portland cement concrete (PCC) and hot mix asphalt (HMA). To determine the specific gravity and absorption of an aggregate blend used in HMA and PCC, the aggregate is separated into two distinct portionsâcoarse and fine aggregatesâbased on a particular grain size (i.e., 4.75 mm). The test methods for coarse and fine aggregate portions are different. Current standard test methods for determining the specific gravity and absorption capacity of coarse and fine aggregates are AASHTO T 85 (or ASTM C127) and AASHTO T 84 (or ASTM C128), respectively. Although these standard test methods can be conducted at a reasonable cost in concrete and asphalt laboratories, they have several shortcomings in terms of subjectivity of mea- surements, precision, and time requirements for condition- ing and testing. Therefore, there is a need to develop new methods or improve the current test methods for determining the specific gravity and absorption of aggregate for use in HMA and PCC mix design/proportioning and production. Project Objectives The overall objective of NCHRP Project 04-35 was to develop improved test methods for determining the specific gravity and absorption of coarse and fine aggregates for consideration by the AASHTO Subcommittee on Materials. Detailed objectives of this project were as follows: ⢠Develop the test methods with balanced improvements in their (1) accuracy, precision, and ruggedness; (2) ease of use; (3) time of conditioning and testing; (4) cost; and (5) ability to uniformly deal with a broad range of natural, crushed, recycled, and manufactured coarse and fine aggregates, compared with current standard meth- ods; and ⢠Address the ramifications of changes to the test meth- ods on HMA mix design and PCC proportioning, other aggregate characteristics, and technician training and qualification. Organization of the Project The project was divided into two phases. The first phase was to identify potential test methods and to plan a labora- tory program for screening and evaluating these methods. The second phase included laboratory programs for evalu- ating those potential test methods, ruggedness studies, and analyses of the impacts of implementation of recommended test methods on current specifications. This report summa- rizes the findings of the project. Introduction
