Abstract
The estimation of elastic modulus for road bases is the primary objective of this research which is implemented a significant role in transmitting the vertical loading to the pavement foundation layers. In this study, the effect of weathering conditions on the stiffness of base course is investigated and implied the durability test by subjecting the prepared samples to a different numbers of wet-dry cycles (0,2, 4, 6, 8 and 10). A conventional base materials of local natural gravel aggregate and treated base materials with recycled concrete aggregate RCA at different percentages (0%, 25%, 50% 75% and 100%) is adopted in this research.
 The elastic characteristics are estimated in terms of elastic modulus. Elastic modulus are estimated by passing the ultrasonic pulse velocity through the untreated and treated base materials laboratory specimens. This test can be used to study the elastic modulus properties of base materials. A multiple linear regression analysis is used for prediction the elastic modulus using the SPSS (software ver.21). Elastic Modulus (kPa) is the dependent variable whereas the independent variable are; No. of wet- dry cycle and Percent (%) of RCA stabilizer. The obtained results for elastic modulus (Es) of granular base material layer showed increasing in elastic modulus with percentage of RCA%., results revealed that the (Es) values reached a maximum value of (6927kPa) for 100%.
 For the OMC’s values increases due to the percentage increment of RCA in granular base material mixture, this increment in water contents is refer to high absorption capacity of the paste clinging to the RCA. On other side the dry density decrease gradually with adding percentage of (RCA) in granular base material mixture.
Highlights
The behaviour and performance of pavements against distresses rutting has significantly influence by the design standard and construction of the granular base layer
The values of optimum moisture content (OMC) and MDD for untreated and Recycled concrete aggregate (RCA) treated granular base samples were depicted in Table (6) and Figure (2) illustrated the relation of water content with maximum dry density for untreated granular base material
Based upon the obtained results for elastic modulus (Es) of granular base material layer, it can be revealed that the (Es) values is reached (6927kPa) higher value for 100% RCA
Summary
The behaviour and performance of pavements against distresses rutting has significantly influence by the design standard (including the estimation of resilient elastic modulus) and construction of the granular base layer. Achieving the long-life of pavements is depending on the control of granular base layer construction quality (Titi, et al 2018). The elastic modulus of granular pavement layers is considered as the most important parameters in pavement design procedures. Various studies have been achieved over the years with respect to engineering properties of granular base materials and the effect of (wet-dry cycles) on such properties. These preceding studies concentrated on mechanical strength properties and how such these properties are affected by weathering impact (Biswal, et al 2018)
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