Execution of large-scale sustainable pavement with recycled materials. Assessment of mechanical behaviour and life cycle

Abstract

It is important to achieve full-scale applications of recycled materials such as pavement concretes, with recycled aggregates and sustainable cements. The objective of this research is the study and full-scale implementation of a concrete road made from recycled by-products. This concrete road must exhibit a compressive strength in excess of 30 MPa (HA-30). A total of 5 different types of sections were included: a control section with conventional concrete, another with the application of Eco-Hybrid additions to the cement, two sections with replacement of aggregates, one with recycled materials from the processing of Mixed Recycled Aggregates (MRA) and the other with MRA and Biomass Bottom Ash (BBA) - and finally, a section replacing both aggregates with MRA and BBA with the use of Eco-Hybrid additions. Characterisation studies of the different materials and the design of the experimental sections were carried out in the laboratory. Dosages and consistencies were controlled at the plant and the mechanical behaviour in the short and medium term was measured externally. For the technical study of concrete behaviour, in situ sensors were included, obtaining monitoring results through temperature sensors and dimensional changes. In addition to a study of behaviour and durability, a life cycle assessment was made to measure the environmental impact of conventional concrete and mixtures with recycled materials using environmental and monetary parameters. The cement that included alternative supplementary cementitious materials at 25 % of the total showed comparable strength to conventional cement. Aggregate substitution of 35 %-40 % resulted in a decrease in mechanical properties between 15 % and 25 %. The environmental impact was reduced between by 10–15 % in mixes in which Eco-Hybrid cement was used.