Test And Research Of Recycled Aggregate Concrete From Road Pavement

1 .Background and ObjectivesSince from the beginning of 21 century, construction industry has come into a high speed developing stage with the acceleration of worldwide urbanization, and the cost to deal with construction waste became more and more high which lead to more and more social and environmental problems. According to some relevant data, construction waste made only from construction process has reach 40,000,000 ton annually 40 percent of which is waste concrete, so the annual production of waste concrete in china account to about 13,600,000 ton. Furthermore, there is a trend to produce much more in the future. Presently, method dealing with construction waste mainly is to transport and place it to environs or bury it underground. But there is a new method crushing, washing and grading these waste concrete blocks, then blending them according to certain proportion into aggregate of new concrete so called Recycled Aggregate (RA). This new concrete made of Recycled Aggregate wholly or partly is called Recycled Aggregate Concrete (RAC). The method of RAC can reuse limited natural resources and resolve environmental problems by reusing a mass of waste concrete, which is one of the main ways to develop green concrete and realize ecotypic construction production.The main research targets of this thesis are presented as follows: theoretical and experimental studies of RAC mix design; experimental contrast and mechanism properties analysis to natural and recycled concretes' liquidity, compressive strength, elastic modulus, frost resistance, penetration resistance and so on; investigation about technical and economical contrast around Chengdu area.2.Theoretical ApproachThe study of the thesis is based on theory of Concrete material science and microcosmic mechanism analysis. Two kinds of RAC with C25 and C30 strength grades widely used in road construction were studied in this thesis. We collected these waste concrete blocks from pavement of rebuilding 1st circle road in Chengdu, and some high-powered Slushing agent is considered to be use. The basicperformances of RA, such as strength, hardness, consistence, sieving, apparent density and so on, all are strictly according to the standards of Test Methods of Aggregate for Highway Engineering (JTJ058-2000). Then C25 and C30 RAC is produced according to performances of RA and the basic performances of RAC, such as slump, concreting period, compressive strength, compressive elastic modulus, breaking strength, frost resistance, penetration resistance and so on, all are strictly according to the standards of Testing Methods of Concrete for Highway Engineering (JTJ053-94). Besides, technical and economical contrast with practical application of RAC is studied and discussed. Finally, the conclusions and suggestions are presented.3.Innovation and LimitationThis thesis strives to make creations and developments on the following respects: (1) in the context of large-scale urbanization and road rebuilding in China, the RAC made from road pavement concrete is studied theoretically and experimentally, in the case of absence of related studies;(2) experimental analysis according to present codes has some referenced value to improve the application of RAC in practice and room for further studies;(3) technical and economical contrast with RAC can be used as reference for further studies.But there are still some aspects of the study to be improved because of availability of data and capability of the writer. For example, the little number of the RA resources samples leads to worse adaptation of analysis results; the circles of freezing and thawing are not enough to show the rules; the microcosmic mechanism analysis need to be improved and adjusted.In addition, many other issues are valuable for further research. For example, because both the sources and performances of RA are very different, how to treat them differently and how to establish a set of evaluation index system for RA grading and quality controlling; how to improve the freezing and thawing resistance of RAC, etc.