Abstract
Recycled materials from construction and demolition waste, such as recycled concrete aggregate, recycled brick aggregate, or recycled asphalt coming from the milling of road/motorway surfaces, are the key for a sustainable production of concrete. This paper reviews in particular the use of recycled asphalt pavement (RAP) aggregates in the production of concrete for structural uses. An overview is initially presented to describe the different areas of use of RAP, its definition and the limitations imposed by codes and standards. Relatively to the experimental data provided by the literature, a comparison with the Italian minimum requirements is also provided. Lastly, the influence of RAP on the characteristics of concrete such as compressive strength, flexural strength, Young’s Modulus and a study of durability are presented to define the possible applications of RAP in structural concrete in relation to the current allowable percentage of substitution.
Highlights
Properties like crushing, impact and abrasion resistance do not usually exceed the limits imposed by the standards expected for the use of recycled aggregates when compared to virgin aggregates, especially if they are used for concrete pavement applications [33]
In [5], other parameters, such as the initial rate of absorption and capillary absorption coefficient, were studied and the results demonstrate that these parameters decrease with the increase in recycled asphalt pavement (RAP) aggregate content: both the initial rate of absorption and capillary absorption decreased by 50% for a mix containing 75% of RAP in relation with a mix with only virgin aggregates
Beyond the mechanical limitations that include the decrease of parameters such as compressive strength, flexural strength, splitting tensile strength and modulus of elasticity as the percentage of replacement of RAP
Summary
The new approach in the engineering field is focused on sustainability by aiming at new solutions able to reduce the greenhouses emissions in the environment; the civil engineering cannot be excluded and it has to contribute to the 2050 decarbonization challenge. If on one side, the concrete production is connected to a high energy consumption, on the other side demolition of concrete structures causes large amounts of waste. In the last few years, researchers [3,4,5] have investigated the possible use of reclaimed asphalt pavement in structural concrete by studying its influence on hardened concrete properties, such as compressive strength, flexural strength, elastic modulus and splitting tensile strength. This paper aims to give an overview of the current applications of RAP aggregates in the construction sector, focusing on their use in structural concrete. Considering the real exploitation of this recycled material, the analysis of the current standards and regulations for the characterization of RAP aggregates and the possible barriers on their use in concrete is presented. The influence of RAP on concrete performance is analysed to investigate the current state of the art and to point out future research directions
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