SUMMARYThe high temperature performance up to 800 • C of combined fly ash (FA) and slag geopolymers at the ratio of 100, 65/35, 50/50, 35/65 and 100% (wt-%) is presented in this paper. Geopolymers are alternative novel binders to conventional Portland cement and are generally believed to provide superior fire resistant properties due to their ceramic-like characteristics. This paper presents new data on the behavior of geopolymers made with combined FA/slag mentioned previously, which were mixed with alkaline materials with molecular silicate modulus (Ms = SiO 2 /Na 2 O) of 0, 0.5, 1.0, 1.5 and 2.0 with sodium (Na) dosages of 4 and 8 (wt-%). Altogether 60 mixes were made yielding compressive strengths between 3 and 83 MPa. Behavior of the material to high temperatures was investigated by exposing the specimens to 800 • C and testing for compressive strengths. It was found that as the initial strength increases, the residual strength exponentially decreased. The compressive stress versus strain relationships showed that the ductility of the specimens decreased as the initial strength increased. The ability of the materials with high ductility (i.e. less brittleness) to accommodate thermal incompatibilities arising from uneven temperatures arising during heating is concluded to be the major factor contributing to the reduced strength losses. Geopolymer has recently emerged as a novel engineering binder material with the potential to form an element of an environmentally sustainable construction product [1,2]. Geopolymers are often compared with the conventional Portland cement since the applications of geopolymers are targeted to replace the conventional Portland cement. Geopolymer is a term used to describe inorganic polymers based on alumino-silicates [3] and can be produced by synthesizing pozzolanic * Correspondence to: Maurice Guerrieri, Department of Civil Engineering, Monash University, Clayton 3800, Australia. 164M. GUERRIERI AND J. G. SANJAYAN compounds or alumino-silicate source materials with highly alkaline solutions [4]. Owing to their ceramic-like properties, geopolymers are believed to possess good fire resistance [5,6]. Geopolymers are also referred in the literature as alkali-activated fly ash (FA) or inorganic polymers [7]. The production of geopolymers has been shown to release 80 to 90% less green house gas emissions than the conventional Portland cement [2]. Each ton of conventional Portland cement production is responsible for the release of 0.7 to 1.0 tons of CO 2 into the atmosphere [8].Ground-granulated blast furnace slag (Slag) and FA, byproducts of iron manufacturing and coal burning electrical power plant industries, respectively, have been used widely either integrated or pre-blended with ordinary Portland cement (OPC) to produce blended cement binders. Slag and FA-blended cements are characterized by their low heat of hydration and high chemical durability and can enhance the physical and mechanical properties of concretes and even provide higher early strength than OPC concretes [9,1...

SUMMARYThis paper reports the effect of elevated temperature exposures, up to 1200 • C, on the residual compressive strengths of alkali-activated slag concrete (AASC) activated by sodium silicate and hydrated lime; such temperatures can occur in a fire. The strength performance of AASC in the temperature range of 400-800 • C was similar to ordinary Portland cement concrete and blended slag cement concrete, despite the finding that the AASC did not contain Ca(OH) 2 , which contributes to the strength deterioration at elevated temperatures for Ordinary Portland Cement and blended slag cement concretes. Dilatometry studies showed that the alkali-activated slag (AAS) paste had significantly higher thermal shrinkage than the other pastes while the basalt aggregate gradually expanded. This led to a higher thermal incompatibility between the AAS paste and aggregate compared with the other concretes. This is likely to be the governing factor behind the strength loss of AASC at elevated temperatures.

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