LEAB-PA, A Half Warm Porous Asphalt Can Increase the Lifetime

Abstract

BAM Wegen constructed the first LEAB (in Dutch: Laag Energie AsfaltBeton; in English: Low Energy Asphalt Concrete) test sections in 2003 Compared to conventional hot produced asphalt mixes, the production temperature of LEAB reduced significantly using foamed bitumen. At first the LEAB concept was applied for asphalt concrete bind and base mixtures (AC bind and AC base mixtures). More recently also test sections with Porous Asphalt (PA) have been built with foamed bitumen. The mixture is called LEAB-PA. The slow lane average lifetime of PA16 in the Netherlands is approximately 11 to 12 years. The fast lane average lifetime is 16 years. The predominant damage of PA is ravelling, which is mainly caused by the ageing of the mortar in the PA mix by oxidation and UV light. The lower production temperature of the LEAB-PA procedure reduce the short term ageing of the mortar in the PA mix. Loss of mortar flexibility in the PA mix by ageing of the bitumen is the predominant factor for ravelling. It is expected that LEAB-PA will have a higher resistance to ravelling and a longer life span in comparison with hot produced PA mixes. Since 2010 different test sections with LEAB-PA are constructed combined with a section of conventional hot produced PA with the same mix composition as a reference. The shear moduli (mastercurve) of the mortar of the LEAB-PA and the conventional PA are monitored periodically using DSR tests. Also the penetration and softening point Ring & Ball of the bitumen are monitored. Additionally indirect tensile strength tests and CPX measurements for noise reduction have been executed. After 3 years of monitoring it is concluded that the difference in ageing between LEAB-PA and conventional PA is still significant. Lower production temperatures reduce short term ageing. Therefore we expect it will increase the lifetime of PA.