Volcanic ash and pumice as cement additives: pozzolanic, alkali-silica reaction and autoclave expansion characteristics Khandaker M. Anwar Hossain * Department of Civil Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario, Canada M5B 2K3 Received 2 February 2004; accepted 20 September 2004 Abstract This study reports the results of investigation to assess the suitability of volcanic ash (VA) and pumice (VP) powder to be used as cement additives. Pozzolanic activity of VA and VP was tested according to the Italian standard and found to be acceptable. The strength activity index with Portland cement and the effectiveness of VA and VP admixture in controlling alkali-silica reaction and autoclave expansion were tested according to ASTM standards. Mortar cubes were specially prepared as per ASTM standards for these studies using different mixes with varying percentages of VA and VP (0–40%) as cement replacement. The results are then compared with ASTM requirements to assess the suitability of VA or VP as cement additives. D 2004 Elsevier Ltd. All rights reserved. Keywords: Volcanic ash; Volcanic pumice; Pozzolan; Alkali-silica reaction; Autoclave expansion; Cement additive 1. Introduction The search for alternative binders or cement replace- ment materials has continued in the last three decades and from the economical, technological and ecological points of view, cement replacement materials play an undisputed role in the construction industry. Comprehensive research has been carried out in the past on the use of fly ash (FA), pulverized-fuel ash (PFA), blast furnace slag (BFS), rice husk ash, silica fume (SF), etc., as cement replacement materials [1–6]. Small amounts of inert fillers have always been acceptable as cement replacement. If the fillers have pozzolanic properties, they impart not only technical advantages to the resulting concrete but also enable larger quantities of cement replacement to be achieved. PFA and FA are pozzolanic materials, because of their reaction with lime that is liberated during the hydration of cement. Amorphous silica present in the pozzolanic materials combines with lime (Calcium hydroxide) and forms cementitious materials. These materials can also improve the durability of concrete and the rate of gain in strength and can also reduce the rate of liberation of heat that is beneficial for mass concrete. Over recent decades Portland cements containing fly ash and silica fume have gained increasing acceptance whilst Portland cement containing natural pozzolans like rice husk ash and burnt oil shale are common in regions where these materials are available. Replacement levels of Portland cement in blended cement containing blast furnace slag vary considerably, and contents of well over 50% by mass are common in some regions. Fly ash typically replaces 10– 30% of the Portland cement although levels of 50–60% have been advocated [6]. When silica fume is added, it commonly comprises 5–10% of the binder. ASTM Stand- ards [7,8,9] exist for the use of natural pozzolans, fly ash, and silica fume and blast furnace slag in concrete. Volcanic activities are common in various parts of the world and due to frequent volcanic eruption, volcanic debris such as: volcanic ash and pumice are found abundantly. The 1994 volcanic eruption that occurred in the East New Britain province of Papua New Guinea was the second most destructive one in history, which completely devastated the 0008-8846/$ - see front matter D 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.cemconres.2004.09.025 * Tel.: +1 416 979 5000x7867; fax: +1 416 979 5122. E-mail addresses: dr _ k _ m _ hossain@hotmail.com, ahossain@ryerson.ca. Cement and Concrete Research 35 (2005) 1141– 1144