Strength and resilient modulus characteristics of emulsion-stabilised demolition wastes in pavement structures

The use of bitumen emulsion has commonly been limited to pavement surface treatments or stabilising virgin aggregates. There is a lack of experimental evidence about the resilient modulus responses of bitumen emulsion-stabilised recycled demolition wastes in pavement applications. The aim of this study is to evaluate the effect of bitumen emulsion on the tensile strength and resilient modulus responses of recycled crushed concrete aggregate and crushed brick for pavement base/subbase course applications. A type of slow-set anionic bitumen emulsion was used at different contents of 0, 1, 2, and 3 % by dry weight of aggregates to prepare compacted specimens. The specimens were dried back to 70 and 90 % of the compaction moisture content to simulate the field conditions. Specimens were next investigated through a comprehensive testing program, including indirect tensile strength, indirect tensile modulus, and repeated triaxial loading tests. Results showed that the tensile strength of the mixtures generally increased as the emulsion content increased. The inclusion of 2 % and 3 % bitumen emulsion to RCC and CB provided the highest indirect tensile resilient modulus (ITMr) at 359 and 310 MPa, respectively, for those samples cured for 3 h. The highest ITMr results were obtained from samples cured for 3 days at 40 °C in a dry state with the inclusion of 2 % emulsion. For CB and RCC specimens, the results were 2808 and 3361 MPa, respectively. However, specimens of CB and RCC with 3 % emulsion that were cured for 3 days at 40 °C and then soaked in water at 25 °C exhibited the highest ITMr at 1981 and 2900 MPa, respectively. The resilient modulus in the majority of the specimens peaked at 2 % emulsion content, which was recommended as the optimum emulsion content. Results also indicated an enhanced resistance to moisture damage in demolition wastes through emulsion stabilisation. This study proposes, validates and promotes the sustainable approach of emulsion stabilisation of recycled aggregates used in the construction of pavement structures.