EVALUATION OF THE 4-CYCLE MAGNESIUM SULFATE SOUNDNESS TEST. FINAL REPORT

This report presents an evaluation of the 4-cycle magnesium sulfate soundness test to control quality of coarse aggregates for use in hot mix asphaltic concrete and seal coats. A total of 41 aggregates were tested for the purpose of this study in the laboratory and the behavior of eight of the aggregates was evaluated in the field by examining roadway performance. The soundness test was found to be the best method for predicting performance among specific gravity, absorption, aggregate durability index, freeze-thaw, Los Angeles abrasion, and a modified Texas wet ball mill (called Texas degradation) tests. Specific recommendations have been suggested to improve the soundness procedure. Also specification limits for hot mix and seal coat projects have been included. The repeatability of the soundness test was approximately equal to that of durability index and lower than the repeatability of Texas degradation. Statistical analysis showed high correlation between soundness and other tests at soundness losses less than 20 percent, and low correlation at higher values. Texas degradation showed the best correlation with the soundness test. The model that describes their relationship has R-squared equals 0.72.