New hot-mix cold-laid mix design method with a superpave gyratory compactor

Abstract

This study introduces a novel method for designing Hot-Mix Cold-Laid (HMCL) asphalt mixes, which are essential for pavement maintenance. In Texas, the current practice for HMCL mix designs adheres to the traditional Hveem method, employing a Texas Gyratory Compactor (TGC) in line with the Texas Department of Transportation (TxDOT) specifications. However, this research advocates for the use of a Superpave Gyratory Compactor (SGC), a more advanced and modern alternative. The SGC, widely used for Hot-Mix Asphalt (HMA) mix designs, provides more adjustable parameters and the ability to control compaction densities. Five types of industrial-based HMCL mixes were examined, each type having three levels of binder content. These fifteen laboratory-mixed HMCL mixes were used to mold SGC specimens at four compaction levels. This established the design gyration for SGC lab-molded densities within 94.0 ± 1.5 %. The investigation revealed that the existing specification might include mix designs with low compactability and weak correlations with field performance, due to their insensitivity to binder contents. The proposed method uses Cantabro mass loss test, IDEAL cracking test, and rutting test to characterize mix resistance to raveling, cracking, and rutting. The binder contents significantly affected these test results, leading to the exclusion of mixes with low compactability during testing. Thus, the new HMCL design method using an SGC enhances the current method.