Quantifying the characteristics of fine aggregate using direct and indirect test methods
The characteristics of fine aggregates, such as shape, angularity, and surface texture, have been shown to influence the performance of concrete and asphalt mixtures and to play an important role in obtaining valuable properties of early age concrete such as workability, and compatibility. However, the measurement of fine aggregate characteristics is not easy. In the present study, 26 fine aggregates, covering a wide spectrum of mineralogy, were examined using direct and indirect test methods in order to evaluate the shape, angularity, and surface texture, as well as to analyze the gradation. The direct test methods, such as AIMS and Camsizer, which provide a digital image of the aggregates proved to be the best. However, the cost of such systems can limit the use of digital imagining systems in practice. The indirect test methods which provide an estimate of aggregate surface characteristics, such as uncompacted void test, mortar flow test, compressive strength test, and flakiness test gave variable results. The uncompacted void test (Method A) was shown to be the most accurate indirect test method. The Camsizer and the sieve analysis test produced identical gradation analysis results when an adequate sample was used. General correlations were developed between the direct and indirect test methods. The non-approved fine aggregates on the TxDOT’s list were analyzed and compared to those of the approved fine aggregates to see whether they could be successfully used. It was found that both LS-5 and LS-8 had good results—even better than the results of some of the approved fine aggregates. Thus, they could be successfully used.