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...
With a growing pipeline of major transport infrastructure projects transforming Victoria's road and rail networks, there is an increase in demand for the construction of underground tunnels using the shield tunneling method. Such tunnels need to be designed for fire resistance in order to preserve both structural integrity and serviceability in the event of a fire event. This paper describes the approach taken to design the concrete tunnel lining segments for Melbourne's Metro Tunnel Project for structural stability during a severe fire incident. Two types of fire testing programs were implemented, both of which used the RABT ZTV (rail) fire curve. The first involved the fire testing of 12 unloaded flat panels in order to determine whether a particular concrete mix design would be susceptible to spalling. Second, six prototype full scale tunnel lining segments were subjected to full scale structural fire testing, for the first time in Australia. The results indicated that full scale structurally loaded fire tests are essential as unloaded flat panels underestimate the degree of spalling. Addition of PP fibers are successful in mitigating spalling in addition to using pozzolans cements such as flyash and slag.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.