ASPHALT MIXTURE PRODUCTION

PMB MIX EXAMPLES

WARM MIX ASPHALT USING POLYMER MODIFIED BITUMEN (PMB)

Warm mix asphalt technologies allow for 20-55°C reduction in asphalt mix production and placement temperature, enabling reduction in asphalt mixture fume emissions and lower fuel consumption during asphalt mixture production. Often these technologies carry an additional benefit of improving the asphalt mixture compactability. [1]
Sometimes a question may arise regarding the compatibility of the warm mix technologies with SBS modified bitumen. The answer to this question is simple: Extensive field experience proves that SBS modified bitumen can be successfully used in conjunction with all 3 warm mix asphalt technology types:
Foaming processes
Wax (organic) additives
Surfactant additives Exemplary projects

FOAMING PROCESSES

Denmark [2]
Polymer modified SMA 11 mix paved by NCC in Denmark on motorway 321 at Ulladulla in September 2012. The temperature was lowered by 20°C as compared to conventional mix production temperature. The mix achieved the same volumetrics and adhesion as traditional asphalt. [2]

United States [3]

Several asphalt pavement test sections were paved at the National Center for Asphalt Technologies as a part of “Green Group” experiment aimed at evaluating different aspects of pavement sustainability. One of the sections, S6, included a 5.8cm thick asphalt base layer containing 25% RA and PG76-22 PMB (~3% SBS). The layer was paved with the foaming warm mix technology enabling the mix placement at 140°C.

ORGANIC (WAX) ADDITIVES

United States [5]
3” mill and overlay test sections were paved in June of 2008 in George, Washington on interstate highway 90. The average daily traffic on the highway was between 6448 and 7327 with 27% trucks. Both test sections consisted of 12.5mm mixture made with 20% RAP and PG76-28 binder. Such binder normally consists of approximately 4 wt. % SBS. One section was produced as hot mix with mix production and at paver auger temperatures of 166°C and 152°C respectively. The second section was produced as warm mix by utilizing 2 wt. % organic additive. The production and at paver auger temperatures were 143°C and 136°C respectively. Pavement densities were achieved successfully at both sections.

SURFACTANT ADDITIVES

United States [7]
Section S5 of the previously referenced NCAT’s “Green Group” experiment utilized a highly modified asphalt mix (7.5 wt. % SBS in bitumen) made with 35% RAP. The mix was used in base pavement layer. Surfactant warm mix additive was used to pave 6.9mm thick layer at 141°C. Poland [6]
Another example of using WMA surfactant technology concerns the application of mastic asphalt on a bridge deck. The mastic asphalt was made with PMB 34/55-80 utilizing the HiMA technology. The addition of surfactant additive ensured excellent pourability of the mix.