Evaluation of Aspha-Min® Zeolite for Use in Warm Mix Asphalt

Several new processes have been developed to reduce the mixing and compaction temperatures of hot mix asphalt without sacrificing the quality of the resulting pavement. One of these processes utilizes the Aspha-min® zeolite, a crystalline hydrated aluminum silicate. A laboratory study was conducted to determine the applicability of Aspha-min® to typical paving operations and environmental conditions commonly found in the United States, including the performance of the mixes in quick traffic turn-over situations and high temperature conditions. Aspha-min® was shown to improve the compactability of mixtures in both the SGC and vibratory compactor. Statistics indicated an average reduction in air voids of 0.65%. Improved compaction was noted at temperatures as low as 190°F. he addition of zeolite does not affect the resilient modulus of an asphalt mix. The addition of zeolite does not increase the rutting potential of an asphalt mix as measured by the Asphalt Pavement Analyzer. The rutting potential did increase with decreasing mixing and compaction temperatures, which may be related to the decreased aging of the binder. There was no evidence of differing strength gain with time for the mixes containing zeolite as compared to the control mixes. There is no indication that HMA containing Aspha-min® requires a cure period prior to opening to traffic. The lower compaction temperature used when producing warm asphalt with Aspha-min® may increase the potential for moisture damage as indicated by tensile strength ratio (TSR) and Hamburg tests. However, the addition of hydrated lime mitigated this effect. A demonstration project was constructed using Aspha-min® zeolite in Orlando, Florida. The warm mix production and compaction temperatures were 35°F less than those used for the control (approximately 300 °F compaction temperature). The laboratory test results on the field mix coincide with the laboratory study. Cores taken one year after placement indicated no increased evidence of moisture damage as compared to the control mix. Overall, Aspha-min® zeolite appears to be a viable tool for reducing mixing and compaction temperatures that can be readily added to hot mix asphalt. Reductions in mixing and compaction temperatures are expected to reduce fuel costs and emissions.