A Study of the Residual Strength of Reactive Powder-Based Geopolymer Concrete under Elevated Temperatures

Thathsarani Kannangara,Maurice Guerrieri,Paul Joseph,Sam Fragomeni

doi:10.3390/app112411834

Abstract

This paper reports on studies relating to the unstressed residual compressive strengths of geopolymer pastes that are heated up to 800 °C, behavior of reactive powder concrete before and after exposure to elevated temperatures and thermal behavior of novel reactive powder geopolymer-based concretes. For this purpose, 10 geopolymer pastes and three reactive powder concrete mixtures were tested for residual strengths. Gladstone fly ash was used as the primary binder for both geopolymer pastes and reactive powder geopolymer concretes. In addition, four novel reactive powder geopolymer concrete mixes were prepared with zero cement utilization. While reactive powder concretes achieved the highest seven-day compressive strengths of approximately 140 MPa, very poor thermal behavior was observed, with explosive spalling occurring at a temperature of ca. 360 °C. The reactive powder geopolymer concretes, on the other hand, displayed relatively high thermal properties with no thermal cracking at 400 °C, or visible signs of spalling and very mild cracking in one case at 800 °C. In terms of the strength of reactive powder geopolymer concrete, a maximum compressive strength of approximately 76 MPa and residual strengths of approximately 61 MPa and 51 MPa at 400 °C and 800 °C, respectively, were observed.

Highlights

Owing to the increasing number of high fire risk infrastructures built around the world, including concrete tunnels, petrochemical plants, nuclear reactors, and oil refineries, concrete structures with a relatively high strength capacity and superior fire resistance are in high demand
It is relevant to note here that the various empirical parameters, such as density, workability, compressive strengths and mass losses, obtained were averaged over triplicate measurements as the spread of values were quite acceptable given the nature of specific measurements in question
This research was focused on investigating the performance of a novel material called reactive powder geopolymer concrete (RPGC)

Summary

Introduction

Owing to the increasing number of high fire risk infrastructures built around the world, including concrete tunnels, petrochemical plants, nuclear reactors, and oil refineries, concrete structures with a relatively high strength capacity and superior fire resistance are in high demand. 1990s by a French Corporation [1] They are currently used as an ultra-high performance concrete, where compressive strengths in the range of 150–800 MPa, tensile strengths between 6–13 MPa, flexural strengths in the range of 30–60 MPa and fracture energy in the range of 1200–40,000 J/m2 can be achieved [1,2,3,4]. Typical dry ingredients of RPC include cement, as the binding material, together with silica fumes, an ultra-fine spherical shaped material, having an average diameter of about 0.15 μm and aggregate fillers, such as silica flour and fine sand/quartz particles, typically less than 600 μm in size [3,6]. The w/c ratio of RPC is reported to be between 0.1–0.25, whereas conventional concretes consist of a w/c ratio between 0.35–0.7 [6]

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Results

Conclusion