Statistical Analyses of Density Measured by Submerged Weight in Water and Saturated Surface Dry for Compacted Hot-Mix Asphalt(HMA) Specimens

There has been much attention given to the determination of the specific gravity(Gmb) of compacted hot-mix asphalt(HMA) specimens.Due to simple and convience,submerged weight in water method is allowed to use for I type mix in design,construction and quality control in China.In order to evaluate the efficacy of the method,a total of 38 compacted HMA specimens are tested by using two test methods:(1) saturated surface dry(SSD);(2) submerged weight in water(SWW).Each specimen is tested two times in each of the two methods.The specimens represented field-sampled and lab-prepared mixtures,three nominal maximum aggregate sizes,and a variety of aggregates typically used in China.Test results indicate that statistically significant differences exist between mean Gmb values generated by the two testing methods.In general,the SWW method yielded the greater Gmb values than SSD.Significant differences in the variability of test results are not observed between test methods.The average Gmb of SWW is 0.028 89 g/cm~3 greater than that of SSD,which results to the more the error of air void 1.1%.The more the mixture absorbs water,the error of air void has greater differences computed by the two methods.It is suggested that the impact of test results on existing volumetric property specifications should be considered and that the SSW method should not be used in the design of proportion of (mixtures.)