Guidelines for Improving the Performance of TxDOT Item 334, Hot-Mix, Cold-Laid Asphalt Concrete Paving Mixtures (1717-S)

TxDOT maintenance personnel have noted problems with a commonly used, stockpiled maintenance mix known as Item 334, Hot-Mix Cold-Laid Asphalt Concrete Paving Mixture (HMCL). It is generally used by maintenance personnel as a blade-on/level-up material and not as a pothole repair material (except when necessary). Performance problems include stripping in the stockpile, a tendency towards instability in hot weather, and a lack of winter workability. The objective of this research project was to identify a series of simple but meaningful laboratory tests and acceptance criteria for HMCL patching materials which will ensure reasonable stockpile life and field performance. The complete results of this research project are presented in research report 1717-1. This report provides a summary of those results and recommendations for implementation.|A literature review was conducted to identify published information on patching materials with a particular emphasis on test procedures developed for maintenance mixtures. A survey was performed of maintenance personnel in all TxDOT district offices to identify problems. Several different HMCL mixtures were designed and evaluated in the laboratory. These mixtures were designed using two types of aggregates (crushed gravel and crushed limestone) and three types of binders (AES-3005, MC-800, and MC-800 with diesel) for a total of six different mixtures. Laboratory tests indicated that mixtures designed at 92 percent density had stabilities and strengths as high or higher than those designed at 95 percent density. Field mixtures were evaluated in the laboratory as a function of stockpile age. The rolling sieve cohesion test was found to be a simple test that adequately measures the cohesiveness of the HMCL materials.