Eleftherios Anastasiou

Cost-effective mixtures for concrete pavements

In concrete pavement construction large quantities of industrial by-products could be absorbed for the benefit of economy and sustainability, especially when large infrastructure projects are in progress. In Greece, a great amount of high calcium fly ash (12 million tons per year) and steel slag (2.5 million tons per year) is produced. The current utilization rate of the above by-products is relatively low. Before their utilization, the local industrial by-products should be tested and used properly to achieve optimum concrete mixtures for pavements. In this paper, local steel slag is used as aggregate in combination with a cement-fly ash binding system for the production of concrete mixtures whose strength ranges from 20 to 70 MPa. Apart from compressive strength, flexural tensile strength, elastic modulus of elasticity, fracture toughness, fatigue strength, and resistance to abrasion have been measured in a series of concrete compositions. Based on the results, it seems feasible to design and apply low-cost concrete mixtures for pavements, since they may contain a considerable amount of by-product for which the main cost is their transportation. The technical benefits related to their use in concrete are also presented.

Feasibility Study and Criteria for EAF Slag Utilization in Concrete Products

The use of industrial byproducts in concrete applications is a scientific area of great interest over the past several years, and steel slags are acknowledged as having great potential for such use; however, the utilization rates are relatively low. The main barriers identified for this occurrence are failure to quantify benefits in terms of quality of the final product, environmental benefits, as well as cost reduction. The present research attempts to quantify these aspects for five different concrete applications examined as case studies. Laboratory-produced alternative concrete mixtures with steel slags are compared with ordinary reference concrete mixtures for their performance regarding mechanical characteristics and durability, environmental benefits using life cycle assessment, and cost estimation. The results show that there is great potential for the use of steel slag in concrete, but the benefits need to be determined for each specific use, since the values observed vary greatly depending on the application. Industrial pavement and heavyweight concretes seem to be the most favorable applications for steel slag, while the shotcrete and repair mortars examined benefited less from the use of slag.

An Investigation of the Behavior of Raw Calcareous Fly Ash in Mortar Mixtures

The behavior of unprocessed calcareous fly ash in cement mortar mixtures is often questionable and unpredictable and that is one of the difficulties in confining these fly ashes within the limits of standards. This work aims at correlating the material characteristics with its behavior in mortar mixtures. An effort is made to understand how three of the reactive constituents; lime (CaO), silica (SiO2), and sulfates (SO3), affect strength and volume stability. Two raw calcareous fly ashes of different composition emanating from the Ptolemaida area, Greece, were systematically tested to define their profile as cementitious agents that could be incorporated in a cement mixture by replacing part of the cement. Apart from chemical analysis, a mineralogical analysis of their phases was carried out by x-ray diffraction and SEM microscopy. Fineness was measured by sieving and laser particle size analysis to identify the most prevalent grain size. In order to measure soundness and water demand of the pastes, the corresponding EN and ASTM standards were followed. A number of specimens were also prepared in order to determine the pozzolanicity index of the fly ashes. Furthermore, mortar mixtures with either calcareous fly ashes as the only binder or in combination with cement (50/50) were prepared both with and without superplasticizers (SPL) in order to monitor strength development. The early deformation of these mortars, stored at low relative humidity (,65%) and a temperature of 20 uC, was also measured. Evaluating all the results, some remarks are made about the performance of the existing standards. It is also obvious that the water/binder ratio is an important parameter which can be modified by using SPL and in this way it is possible to improve significantly strength and volume stability of cement-fly ash mortar mixtures. f 2010 The University of Kentucky Center for Applied Energy Research and the American Coal Ash Association All rights reserved. A R T I C L E I N F O Article history: Received 25 September 2009; Received in revised form 30 December 2009; Accepted 15 January 2010