Pobierz pełny numer 1/2010 S&E - Structure and Environment - Kielce

MAREK IWAŃSKIGRZEGORZ MAZUREKKielce University of TechnologyAl. Tysiąclecia Państwa Polskiego 725-314 Kielce, Polande-mail: iwanski@tu.kielce.ple-mail: mazurek@tu.kielce.plA b s t r a c tTHE IMPACT OF AGING ON WATER AND FROSTRESISTANCE OF ASPHALT CONCRETEWITH LOW – TEMPERATURE BITUMENThe application of low – viscosity (low – temperature) bitumen in asphalt concrete results in an improvement of its mechanicalproperties (Marshall stability and deformation, static creep modulus and indirect tensile strength). The tests conducted withthe procedures LTOA (long term aging) and STOA (short term aging) according to SHRP methodology prove that use oflow – temperature bitumen results in slowing down the aging process of asphalt concrete. The dynamics of this process isslower than in case of traditional bitumen. The measurements of water and frost resistance (according to AASHTO T283)of asphalt concrete and of its resistance to low – temperature cracking (according to PANK 4303) have showed that the useof low – temperature bitumen results in higher resistance to weathering than that of the road bitumen 35/50 as a binder.The paper was presented at the International Conference on Maintenance and Rehabilitation of Pavements andTechnological Control in Torino, Italy.Keywords: asphalt concrete, low viscosity bitumen, asphalt weather resistance, LTOA, STOA, AASHTO T283, PANK 43031. IntroductionAsphalt pavements are subject to various defects.They are the results of the combined impact oftraffic and weather factors. This impact causes theconstant changes in stress, deformations, temperatureand humidity. Bitumen and asphalt concrete arethermoplastic materials. Temperature causes changesin their consistency. High temperature leads to lowerviscosity, cohesion and adhesion. When temperaturefalls the binder and asphalt concrete become stiffer.The materials become breakable and prone to crackingas a result of contraction in low temperatures. Theefficiency of mixes produced in „hot” technologydepends on many factors. Some of them are: theinteraction between durability of the mixes due tothe effects of traffic and weather resistance (waterand frost). The mixes made from best materials andmodern technology will not perform well if they aresubject to water and frost. Therefore the water andfrost resistance tests are important factors in design ofthe composition of an asphalt concrete.Asphalt concrete should also meet other functionalitycriteria, such as: fatigue crack, thermal crack, hydraulicconductivity and workability during disintegrationand compaction processes. To obtain asphalt concretewhich is resistant to the formation of ruts the amountof bitumen needs to be reduced. But then the numberof created voids is higher and the energy consumptionincreases. Maintaining this relation reduces, however,the resistance of the mix to cracking and reduces waterand frost resistance. The lack of durability to water andfrost is caused by two factors: an excessive numberof voids and the insufficient amount of the plasticmass. The aging process needs to be considered too.Regardless of the kind of mix it has an impact in theproduction and operation processes. Limiting the agingprocess requires the reduction in the void fraction andthicker coating. Therefore the compromise between themineralogical composition and the amount of bitumenshould be found.One of the ways of solving these problems is theuse of low – viscosity bitumen. Other componentswhich lower viscosity in higher temperatures havebeen added. They are aliphatic hydrocarbons of longchains. Bitumen of this kind has higher softeningpoint and lower viscosity at 25 o C [4].24