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Using recycled aggregate from construction and demolition (C&D) wastes as a construction material is a potential method for solving the disposal of C&D wastes, which can reduce the exploitation of natural aggregate. In this study, extensive laboratory tests were carried out to investigate the reliability of the C&D wastes used as road base material. Meanwhile, the gradation design and the dominant aggregate size range were considered, and a physical disposal method was proposed to enhance the structural performance of the recycled material by replacing the skeleton of the recycled aggregate (RA) with high-quality limestone. The test results showed that (1) given the high absorbency and fragility of C&D wastes, its RA was not enough to provide the strength and stability required by the base; (2) the compaction characteristics of the RA are quite different from that of the limestone aggregate, but the final compaction effect is basically the same; (3) the replacement treatment proposed in this study is an effective approach to improve the performance of the recycled granular base because the breakage rate decreased by at least 28.2% and the mechanical properties increased by approximately 50% compared with that of the untreated specimen; and (4) when the limestone content reached 75%, the California bearing ratio and the resilient modulus of the graded B specimen exceeded 120% and 200 MPa, respectively, satisfying the pavement requirement in medium traffic. [ABSTRACT FROM AUTHOR]

• The use of Solution Road RomixSoilfix in granular base material is evaluated. • Deformation performance of SRX-GBM in different stress states is analyzed. • Field application and evaluation of SRX-GBM are performed in highway. Granular base material (GBM) is widely used as a base course in flexible pavement, since it has good performances to disperse stress and resist deformation. However, due to the increasing cost of pavement construction resulted by the low stiffness of GBM, the application of flexible pavement was rarely reported in Chinese expressways. This paper aimed to investigate the effect of Solution Road RomixSoilfix (SRX) on deformation performance of GBM and to evaluate the feasibility of SRX modified GBM (SRX-GBM) as a flexible base in expressway structure. A series of experimental tests were performed to analyze the influence of SRX content on curing process, stability and deformation performance of SRX-GBM. Subsequently, a flexible pavement was constructed using the SRX-GBM base course at the field sections on Tengchong to Longchuan Expressway in Southwest China. Results show that the use of SRX improves the California bearing ratio (CBR) of GBM, which raises from 145% to 417%. The dry shrinkage resistance and water stability of SRX-GBM are obviously better than cement-stabilized macadam. The results of triaxial tests demonstrate that the resilient behavior of SRX-GBM is dependent on the stress characteristics and curing times. The existing stress-related model is available for evaluating the changes of stress contribution to the Mr with the increase of SRX content. Since the base course has a high residual moisture content in a humid climate, the CBR of 250% was proposed by field CBR and deflection tests as a criterion for controlling curing time. [ABSTRACT FROM AUTHOR]