Recycled aggregate concrete sound barriers for urban freeways

An increased rate of construction and demolition (C&D) waste generation in the Melbourne metropolitan area has a two-way impact, viz., a rapidly disappearing available landfill space and depletion of natural resources. As a result, there is government and community pressure to reduce the volume of waste by recycling of the waste material and the reuse of its products. This paper focuses on the enhancement of concrete waste products to improve their use in the manufacture of new products. This approach has already resulted in the confirmation that Recycled Concrete Aggregate (RCAG) can be a suitable substitution for the coarse aggregate fraction in production of pre-mixed concrete. The current research focus is on understanding of two of the properties of RCAG and their impacts on strength, durability and the acoustic performance of new concrete. Firstly, the presence of any chemical impurities and their effect on microstructure development, and secondly, the porosity of the cement paste component of the aggregate and its effect on the acoustic performance of concrete, made from RCAG, are examined. The aim of the research is to develop structurally sound Recycled Aggregate Concrete (RAC) with a good sound absorbing characteristics, and to use it in the manufacture of sound barriers for urban freeways. Preliminary results clearly indicate that the porosity of RCAG is more than that of normal concrete aggregate and this has an advantageous impact on the sound absorption coefficient of RAC, and that the strength of such concrete is more than adequate for the intended application.