Recycling of geopolymer concrete

• The properties of recycled geopolymer aggregates (RGAs) are studied.
• The properties of geopolymer concretes made with RGA are studied.
• Recycling is an effective strategy for dealing with geopolymer concrete debris.

Due to its considerably lower embodied carbon and making use of industrial by-products including fly ash and ground granulated blast-furnace slag, geopolymer concrete (GPC) is considered as a sustainable alternative to Portland cement (OPC) concrete. However, prior to granting GPC a green label and encouraging its widespread use, a number of other important possible impacts associated with this new material throughout its life cycle need to be further investigated. One of the important aspects of sustainability which has received little attention with regards to GPC is the end-of-life impact. While end-of-life strategies such as recycling and reuse have been widely investigated for conventional concrete, the applicability of such strategies to GPC has not been investigated. This paper presents the results of an experimental study conducted to investigate the recyclability of GPC. Basic properties of recycled geopolymer aggregates (RGAs) including water absorption, density and Los Angeles abrasion loss as well as the effects of size of RGA on these properties were investigated. In addition, the effects of the different replacement ratios of coarse RGA for coarse natural aggregates on the properties of the new recycled aggregate geopolymer concrete (RAG) including compressive strength, flexural strength and modulus of elasticity were investigated. The RGA and RAG properties were compared with those of recycled OPC concrete aggregate (RCA) and recycled aggregate OPC concrete (RAC) produced under relatively similar conditions.