Effects of mix composition and water–cement ratio on the sulfate resistance of blended cements.pdfVIP

/locate/cemconcomp Cement Concrete Composites 29 (2007) 159–167Effects of mix composition and water–cement ratio on the sulfate resistance of blended cements M. Sahmaran *, O. Kasap, K. Duru, I.O. Yaman Department of Civil Engineering, Middle East Technical University, 06531 Ankara, Turkey Received 26 January 2006; received in revised form 22 November 2006; accepted 23 November 2006 Available online 8 January 2007Abstract This paper presents an experimental investigation on the sulfate resistance of blended cements containing various amounts of natural pozzolan and/or Class-F fly ash. The performance of blended cements was monitored by exposing the prepared mortar specimens to a 5% Na2SO4 solution for 78 weeks. For comparison, an ordinary Portland cement (produced with the same clinker as blended cements) and a sulfate resistant Portland cement (produced from a different clinker) were also used. In addition to the cement chemistry, water– cement (w/c) ratio of mortars was another parameter selected that will presumably affect the performance of mortars. The experimental results of expansion measurements showed that the effect of w/c ratio was more pronounced for the low sulfate resistant cements with higher C3A amounts, while the blended cements were less affected by an increase in the w/c ratio.  2006 Elsevier Ltd. All rights reserved. Keywords: Blended cement; Sulfate attack; Fly ash; Natural pozzolan1. Introduction External sulfate attack which was first identified in 1908 by the United States Bureau of Reclamations [1] is one of the durability problems associated with concrete. Since its identification it has been the subject of numerous studies and still not totally understood [2]. The extent to which concrete is affected by sulfates depends on several factors including its permeability, water to cement (w/c) ratio, type of cement, exposure conditions and the environment [3]. Assuming the same environmental conditions, two factors will tend to control the res