Many benefits are attributed to the use of styrene-butadiene rubber (SBR) latex in asphalt concrete pavements. These include decreased temperature susceptibility, increased rut resistance, and increased resistance to stripping. Potential benefits of SBR latex in hot mix asphalt mixtures were evaluated, and the results of the first 1 V2 years of a 5-year study are reported. Six existing test sites were identified and selected for evaluation. The test sites were located throughout Alabama, and each contained a control mixture and SBR latex modified mixture. Condition surveys were performed at each site to compare performance parameters such as rutting, transverse cracking, raveling, and bleeding. The Alabama Highway Department's pavement management data base provided additional data. The data base was investigated to compare performance of pavements with the department's 416 (control) and 417 (SBR latex modified) surface mixes. The parameters analyzed included mean (rut depth/sqrt ESAL), present serviceability index, friction number, condition rating, and transverse cracking. On the basis of preliminary results, no significant long term benefits can be attributed to the use of SBR latex in dense graded asphalt mixtures. However, further testing is required to verify the results.

Synthetic latexes have been used in asphalt pavements for a number of years. Evidence indicates that the use of synthetic latexes in surface treatments improves chip retention and results in improved performance. Synthetic latex has also been used with success on open-graded friction course projects to improve the adhesion of the asphalt cement to aggregate and reduce raveling. More recently, synthetic latex has been used in hot mix applications, and the reports to date indicate mixed performance. Sometimes the latex improves the performance of the mixture and sometimes it does not. Thus, it is not clear whether the increased cost of this additive is justifiable.