Abstract
The performance and durability of the asphalt pavement structure mainly depend on the strength of the bonding between the layers. Such a bond is achieved through the use of an adhesive material (tack coat) to bond the asphalt layers. The main objective of this study is to evaluate the effect of moisture in conjunction with repeated traffic loads on the strength of the bonding between asphalt layers using two types of tack coats with different application rates. Using the nominal maximum size of aggregate (NMAS), the layers were graded (25/19) and (19/9.5) mm. The slabs of multilayer asphalt concrete were prepared using a roller compactor using two types of tack coats to bond between layers, namely rapid curing cut back asphalt (RC-70) and cationic medium setting emulsion (CMS), with different application rates. Six extruded cores with a diameter of 116 mm each form the prepared slab has been obtained. Core specimens were subjected to moisture damage according to the American Association of State Highway and Transportation Officials (AASHTO), after which repeated bond shear stresses and monotonic tests are practiced. It is concluded that permanent deformation increased with moisture-induction under repeated load for both interfaces and tack coat types. The (CMS) as a tack coat had less permanent deformation values than RC-70 for both interface types and all application rates. In contrast, the interface bond strength (IBS) value was higher than that for (RC-70) in both interface types after moisture conditions. The trend of the results illustrates that (IBS) decreased with moisture conditions under repeated load, as compared to samples under repeated load only.
Highlights
تقييم تاثير ضرر الرطوبة تحت تاثير الحمل المتكرر على قوة ربط السطح البيني متعدد الطبقات للخرسانة الاسفلتية
Its effect appears in the case of water entering quickly into the pavement structure because of the weak bond, causing the pavement to fail within a few years of construction (Sha, 1999). (Al-Qadi et al, 2008) reported that the influence of moisture is reflected upon the strength of bonding between rigid and flexible pavements
It was found that the bonding strength decreased by 43% for the standard samples, whereas for the striping–sensitive binder mix, the bonding strength decreased by 67% after exposure to moisture. (Ghabchi et al, 2017) observed that moisture conditioning reduced the interface shear strength values when no tack coat has been applied
Summary
تقييم تاثير ضرر الرطوبة تحت تاثير الحمل المتكرر على قوة ربط السطح البيني متعدد الطبقات للخرسانة الاسفلتية. Emulsion and asphalt binders are used to bond the layers and to provide an integrated pavement structure that works as a single layer resistant to traffic loads and weather conditions, aiming to prevent premature failure (Mohammad et al., 2002). The weak bonding between the two layers of the hot mix asphalt (HMA) causes many problems, fatigue cracking, top-down cracking, slippage, and delamination Such bonding results in a real tension on the bottom of the surface layer, where the stress concentration accelerates fatigue cracking and eventually leads to the failure of pavement structure (Mohammad et al, 2002; West et al, 2005).. The present investigation aims to assess the influence of moisture under repeated load and the use of two types of tack coat on the permanent micro-strain and interface bond shear strength of multilayer asphalt concrete. The materials used in this study were estimated conferring to the ASTM standard specification and compared with the requirements of the (SCRB, R/9 2003)
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