CARBONATION CHARACTERISTICS OF IN- SITU PORTLAND CEMENT AND FLY ASH CONCRETES IN AUSTRALIA, ENGLAND AND THE UNITED STATES

Abstract

During 1984 and 1986, a series of studies was carried out by the University of Sydney, the National Building Technology Centre and Monier Resources concerning the long-term durability of fly ash and ordinary Portland cement (OPC) concretes in civil engineering and building structures* This paper considers some of the data generated from those studies relating to carbonation of concretes. Measurements of carbonation were obtained from site concretes and correlation analyses between carbonation and other mix design variables of the concretes were carried out. Structures considered in Australia were Keepit Dam and the Outfall Canal at Munmorah Power Station. In England, the structures considered were three Strainer and Isolater Towers at Tilbury Power Station, Clatworthy Dam and two road bridges crossing the M56 Motorway in North-West England. Structures considered in the United States were Hartwell Dam, the Atlanta Steam Generating Plant and the core of the Citizens and Southern Bank Tower Building. All structures were wholly or partly constructed using fly ash concretes. In some cases, similar concretes constructed with and without fly ash were studied. Amongst other factors, the structures were chosen because of their long service histories. Most of the structures have been in service for over 18 years. Relationships between concrete carbonation and water: cement ratio, water:cementitious ratio, cement content, cementitious content and the age of the concretes were investigated. Multiple-regression techniques were used to examine the relationships and conclusions were drawn based on these data. Some comparisons between results of these and other reported studies were also carried out.