Warm Mix Asphalt - Aapaq.org

Example Field JobsA few examples of WMA field jobsthat had been carried out by using the additivesdescribed above are presented here.A field test was carried out in Francefor a rolling surface. 500 tons of BBSG 0/10 mix,(beton bitumineux semi-grenu) were producedfor a two lane road on an industrial area.The asphalt mix formula used contained10% of recycled asphalt pavement (RAP)and 5.4% of bitumen with a penetration gradeof 35/50 [1/1 Ommj . Only 3kg of additive per tonof bitumen was used (about 160g of additiveper ton of asphalt mix). The asphalt mixwas produced at a temperatureof about 135°( and was placedand compacted, after a hauling time of 40min,at a temperature of 125°( in the same wayas a standard HMA. Density measurementstaken during the pavement operation(40 measurements taken bygamma densimetry) showed that an averagedensity of 2.367t1m 3 was achieved.This value is well between the requireddensity limits for this kind of pavement(2.406t1m 3 > density > 2.312 tlm 3 ).Roughness measurements also showeda correct value. This job was in factcarried out next to a previous WMA test jobwhere a similar BBSG asphalt mix formula,without the recycled asphalt pavement.After two years of use, the previous sections,a WMA and comparison HMA,are in perfect conditions.A road construction job of 3,600 tonswas for a heavy traffic two lane roadof an asphalt mixture denominatedEME in France (enrobe a module eleve)was produced at lower temperatureswith the used of the before mentionedliquid chemical additives.This asphalt mixture formula is usedas a base layer capable of withstandingheavy traffic. The EME is characterized due tothe lower penetration grade of its bitumen,10/20 [1/10mmj. For this joba 10cm thickness layer was paved.The chemical additive was addedduring the bitumen-storing tank fillingat 0.4 wt%. The asphalt mixturewas produced at a temperature of 130°( ,where regularly is done at 170°(,The laying down and compaction operationstook place at temperatures below 130 0 (without any problems. Density measurements(approximately 25 measurement per laneshowed that an average valueof void percentage of 4.3% was obtained,with a 100% of measurements below 8%.The required maximum average void percentagewas 6%, with 95% of the measurementsbelow 8%. Laboratory studies also showedthat the Duriez test for this formula(water damage resistance test),at the warm mix asphalt conditions usedin the field job, gives a ratiobetween the conditioned and dry specimensof 0.78 (where a value higher than 0.7 is required).A 8km section of rolling surface for a Frenchhighway was also carried out at warm asphaltconditions by using the discussed chemical additives.In this case, an asphalt mix formula coinedBBTM (beton bitumineux tres mince)was used. This kind of surface is placedfor heavy traffic on a very thin layer,about 2 to 3cm in thickness.The BBTM contains a polymer-modifiedbitumen (PM B). The mix was producedat 130 0 ( and placed at 120°(,while compaction took placeat about 11 OO( (given the small thicknessof the layer, cooling kinetics are faster).This kind of mix is usually doneat a temperature of about 170 0 ((because of the polymer modified bitumen).No problems were encounteredduring the production of paving. Laboratorystudies done before starting the jobdemonstrated that the asphalt mix carriedat the lower temperatures complied withthe requirements (void % and rutting) .A Duriez test showed a ratioof the conditioned sample to dry sample of 0.92.Photos 1 and 2 show the job during paving. »>Photos 1 and 2Paving of a highway section in France using warm mix asphaltsproduced with chemical additiveseuropeanroads review 1 B • Spring 2011 • RGRA IIIIiD