Pumice based blended cement concretes exposed to marine environment: Effects of mix composition and curing conditions Khandaker M. Anwar Hossain * Department of Civil Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario, Canada M5B 2K3 Received 9 June 2006; received in revised form 20 May 2007; accepted 24 May 2007 Available online 15 June 2007 Abstract Results of an investigation on concrete specimens made with different plain (ASTM Type I, II, and V) and blended cements incor- porating different percentages of finely ground pumice up to 30% (as cement replacement) exposed to marine environment for a period of 1 year are presented. Different combinations of mixing water and initial curing conditions simulating cast-in-situ and precast conditions of concreting in marine environment are studied. Blending of Type I and Type II cements with pumice (between 10% and 20%) has shown better resistance against seawater attack than Type V cement with low C 3 A. The performance of pumice based concrete mixtures is assessed based on the strength reduction criteria and is supported by data from rapid chloride permeability, porosity and differential scanning calorimetry tests. It is recommended that Type I cement with pumice content between 10% and 20% would be a better choice in marine environment. Results also show that the use of precasting instead of casting-in-situ could considerably mitigate the deleterious effect of marine environment on concrete specimens. Ó 2007 Published by Elsevier Ltd. Keywords: Blended pumice cement concrete; Marine environment; Compressive strength; Permeability; Porosity 1. Introduction The search for alternative binders or cement replace- ment materials has been continued for the last several decades. Research has been carried out on the use of volca- nic ash, pumice, fly ash (FA), blast furnace slag, rice husk ash, silica fume etc. as cement replacement material [1–6]. Volcanic ash, pumice and FA are pozzolanic materials, because of their reaction with lime (calcium hydroxide) lib- erated during the hydration of cement. Amorphous silica present in the pozzolanic materials combines with lime and forms cementitious materials. These materials can improve the durability of concrete and can also reduce the rate of liberation of heat due to hydration, which is beneficial for mass concrete. Comprehensive research has been conducted over the last few years on the use of volcanic ash and pumice in cement and concrete production [1,7–9]. The meaningful use of such volcanic materials can transform them into nat- ural resources and can provide low cost cement and con- crete. Research suggested the manufacture of blended cements incorporating up to 20% volcanic ash and pumice as replacements of Portland cement [1]. It is essential that the concretes made with volcanic ash and pumice based blended cements should preserve their durability throughout the intended service life of struc- tures. Until recently little research had been conducted on the degradation of such concretes subjected to aggres- sive marine environment [2,10–13]. The concomitant presence of sulfate and chloride ions in marine environments causes deterioration of reinforced concrete structures and reinforcement corrosion. The effect of the conjoint presence of chlorides and sulfates on the sulfate resistance of hydrated Portland cements is inconclu- sive and highly debated [14,15]. The sulfate ions react with the hydration products of cement, namely C 3 A and Ca(OH) 2 , to produce expansive and/or softening types of 0958-9465/$ - see front matter Ó 2007 Published by Elsevier Ltd. doi:10.1016/j.cemconcomp.2007.05.013 * Tel.: +1 (416) 979 5000x7867; fax: +1 416 979 5122. E-mail address: ahossain@ryerson.ca www.elsevier.com/locate/cemconcomp Available online at www.sciencedirect.com Cement & Concrete Composites 30 (2008) 97–105