Mix Design, Modelling and Analysis of Low Carbon Concrete
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Concrete is the most used building material. Mainly Portland cement is used for binding the aggregate. Manufacturing of cement is energy intensive and carbon-dioxide producing process. About 8% of worlds carbon-dioxide is produced by cement industry. Alternative binders, like fly ash and iron slag waste, have been investigated for decades, but only during the last decade the Alcali- Activated Materials (AAM) raised some hopes for more energy saving and ecological concrete production. The chemical durability of the AAM concrete has been investigated quite intensively, but hardly nothing is known of the strength and fatigue behaviour of it. The carbonation behaviour of electric arc furnace (EAF) slag and assessed both EAF and basic oxygen furnace (BOF) slags as supplementary cementitious materials (SCMs) have been investigated. Aqueous carbonation of EAF slag proved more effective than slurry carbonation. EAF slag showed delayed alite hydration but enhanced aluminate reactions, leading to higher strength compared to the Portland cement–limestone reference. Compression tests and notched three point bending flexural tensile tests have been performed. The specimens were loaded to different damage levels. Strains were measured using DIC and post-mortem damage pattern characterized by XCT. Algorithms were developed to post-process XCT images to separate air bubbles from cracks. Mesoscale simulations of concrete have been carried out using Abaqus finite element software consisting of aggregates, voids, AAM cement matrix and ITZ as cohesive elements. Rankine tension cutoff model is applied to the cement matrix and the aggregates, with different material parameters. The finite element model is generated from the XCT images and is therefore an exact geometrical representation of the tested specimen. Tensorial continuum damage model has been further developed and analysed.