Performance and environmental life cycle assessment of ternary blended geopolymer concrete for pavements on military airbases

Abstract

The performance of reinforced concrete pavements in military airbases subjected to regular oil spillage and subsequent flame exposure from turbo engine or exhaust deteriorate rapidly over time making cement concrete a substandard material for the designated purpose. Geopolymers offer better mechanical performance and resistance to aggressive environments under these circumstances. The present study evaluates the mechanical and durability performance of various geopolymer concretes designed from fly ash, blast furnace slag and metakaolin activated by sodium hydroxide and sodium silicate solutions. Two curing regimes, ambient room curing and 70⁰ C curing for 24hrs have been adopted to verify the influence of curing temperature on the concrete properties. To mimic the airbase apron conditions, the samples have been submerged in aviation oils and subsequently exposed to flame to check their mechanical strength and dimensional stability. Though samples made from combination of fly ash, slag and metakaolin in the ratio of 20 %, 50 % and 30 % by weight respectively, displayed better mechanical performance, resistance to acid and aviation oils test, it offered poor workability with minimal setting making it difficult for field applications. Geopolymer mix with fly ash, slag and metakaolin in 40 %, 30 % and 30 % by weight have displayed acceptable durability performance and superior mechanical strength with good workability making it an ideal design mix for airbase applications. The study also evaluates the environmental life cycle assessment (cradle to gate) of the geopolymer concrete and compares them with a 35 MPa cement concrete. All geopolymer concrete mixes on average displayed 60 % less global warming potential in comparison with cement concrete. Geopolymer mixes containing metakaolin, displayed higher mineral resource depletion compared to their cement concrete counterpart.