Use of excavated rock material from TBM tunnelling for concrete proportioning
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This thesis studies the possibilities to utilize excavated rock material from tunnel boring machines (TBM) for concrete proportioning. Available alluvial sand deposits are becoming scarce on a global scale and crushed rock are normally the replacement. Tunnel boring machines (TBM) grinds the rock when excavating and produces a granular material which has potential as concrete aggregates. Utilizing this material has proven to be a viable alternative to the natural sand, additionally influencing the environmental and economic interests. A list of earlier TBM projects where spoil has been utilized into concrete aggregate are listed. Particle size distributions (PSD) from earlier TBM projects are investigated with focus on the filler content. Impurities in concrete aggregate and chemical reactions such as Alkali-silica reaction, mica and sulphur are obstacles in terms of utilization. High filler content in TBM spoil (10-20%) can be utilized with the knowledge of its effect on concrete and using a newly developed micro proportioning principle. Introductory an overview of TBMs and the boring process are presented and the parameters influencing the PSD are described. Concrete aggregate requirements and proportioning with Alkali reactive aggregates. Different material processing methods are presented, including potential crushing, screening and classification machinery for processing of spoil. Field research has been done at TBM projects Follo line and Ulriken in 2016/2017. Collected spoil was investigated in terms of utilization into concrete aggregates. The choice of sieve mechanism in (wet or dry) <0.125 mm fraction impacts the accuracy. Further experiments include the TBM filler composition and behavior in a cement paste to evaluate rheology.