Sensitivity of ASTM D7000 Sweep Test to Emulsion Application Rate and Aggregate Gradation

Abstract

Presented in this paper are the effects of emulsion application rate and aggregate gradation on the performance of chip seal samples prepared and tested according to the ASTM D7000 Standard Test Method for Sweep Test of Bituminous Emulsion Surface Treatment Samples (sweep test). Aggregate loss of the samples was used as a performance indicator for chip seals. Limestone and granite aggregates were tested, and each aggregate type was tested with two gradations. Tests were carried out with three emulsion types: CRS-2, HFRS-2L, and HFRS-2. Each emulsion was tested at three application rates. Samples were tested at two different curing times, 2 h and 6 h. Statistical analysis of the chip loss results revealed that the current sweep test was not sensitive to emulsion application rate in the range tested. Results showed that gradation was a statistically significant factor. Coarse-graded aggregates resulted in high aggregate loss compared with fine-graded aggregates. From the overall results of the study, it is concluded that the current sweep test protocol is not suitable for use as a chip seal design tool because of its insensitivity to emulsion application rate. The test, however, is very sensitive to the combination of emulsion type, aggregate mineralogy, and gradation. It is recommended that the procedure be changed to use aggregate gradations representative of field aggregate. It is also recommended that the sweep test, with minor modifications, be used for evaluating compatibility between emulsions and aggregates and for estimating curing times required.