Recycled aggregate concrete acoustic barrier

This document reports on a research project aimed at developing a concrete acoustic barrier made from Recycled Aggregate (RA) Concrete. The research project was undertaken in response to the needs expressed by the Victorian concrete recycling industry. The industry, the scientific community conducting research into relevant disciplines, and the community at large, represented by Victorian government agencies, are of the opinion that there is a need to devise a higher value utilisation application for selected concrete recycling products. This document outlines the rationale and objectives of the research project which involves the examination of Recycled Concrete (RC) Aggregate, the design and examination of RA Concrete, and finally the development of an acoustic barrier made from RA Concrete. The literature review presented in this report examines aspects of concrete recycling and concrete technology pertaining to traditional and alternative constituent materials for concrete production. Firstly, the importance and influence of fine and coarse aggregate on basic properties of concrete is introduced. Secondly, an account on the use of alternative materials in concrete technology, especially of coarse recycled aggregates and supplementary cementitious materials (SCM) is described. Thirdly, some of the physical and mechanical properties and how the use of RC Aggregate and SCM changes these properties are discussed. Fourthly, a number of commonly used techniques and neutron scattering techniques to investigate aggregate and concrete properties are introduced and discussed. Fifthly, the porosity of aggregate and concrete including durability are specifically discussed and testing methods are reasoned. The literature review also discusses the use of no-fines concrete; its physical, mechanical and acoustic properties. Finally it presents an account of the use of concrete in transportation traffic noise attenuation devices. This document continues with an outline of a methodology that was adopted in this research project. It outlines experimental work aimed at examining the properties of RC Aggregate which amongst other properties includes porosity, particle size distribution, water absorption, shape and density. It continues examining RA Concrete properties and includes, among other properties, compressive strength, porosity and durability as well as sound absorption of acoustic barrier. The methodology introduces standard and purposely modified test procedures used in the examination of aggregates, concrete and acoustic barrier. An account of various research techniques is presented, spanning from simple visual observations to more sophisticated neutron scattering techniques. The summary of test procedures follows a description of test specimen composition and their sizes, and a suite of tested specimens. It also introduces statistical methods used to analyse test results. After a detailed description of the aggregate, concrete and RA Concrete acoustic barrier, the document outlines a summary of data generated through the experimental program of this research project. The data on fine aggregate, on selected 14/10mm coarse RC Aggregate, on concrete made from natural and recycled aggregate and on acoustic barrier are presented and discussed. Test results of various physical, mechanical and acoustic properties of aggregate, concrete and barrier are reported, analysed and discussed. The data from observations, visual assessment and scientific experimentation of specific properties are then crossed analysed in a search for relationships between properties of fine and coarse aggregates and properties of concrete made from such aggregates. A cross analysis of data on 'less-fines' RA Concrete and on the acoustic performance of barrier is examined, and the relationship between the volume of interconnected voids in a porous part of 'less-fines' concrete, and the sound absorption of acoustic barrier is discussed and reported. The document then presents a synthesis of the literature review results, project aims adopted within the experimental program and test results in the three main areas of this research project. These areas include recycled concrete aggregate, recycled aggregate concrete and acoustic barrier made from RA Concrete. Finally, conclusions reached through the course of this investigation are summarised and recommendations are proposed in relation to the RA Concrete acoustic barrier. The main conclusion is that selected RC Aggregate can be used in the production of concrete of a compressive strength of 25MPa, if the moisture content and water absorption in the aggregate are closely monitored, and the foreign material content is kept below 1.5%. The author concludes that acoustic barrier made from selected RC Aggregate has unique sound absorption characteristics that can easily be tunable by a selection of appropriate aggregate and by specific concrete mix designs. Recommendations for further research are also proposed.