Optimization approach for calcined clay and slag based geopolymer mortar – an experimental investigation for 3DCP

Abstract

After water, concrete is the most used substance on the planet. Approximately three tonnes of concrete is produced per person annually (Gagg, 2014). Traditionally, large amounts of Ordinary Portland Cement (OPC) are needed for the production of concrete. The production of OPC is very energy intensive and therefore a major generator of carbon dioxide, which is considered to be a potent greenhouse gas. High CO2-emissions are caused by calcination of limestone and combustion of fossil fuel during an energy intensive production process.
To reduce the CO2-emissions caused by the concrete manufacturing, there is a growing interest in alternative and low CO2-binders. A great example of alternative binders are alkali-activated materials (AAMs), often referred to as geopolymers. Alkali-activated materials are inorganic polymers acting as the binder agent in concrete, often containing by-products from the industry such as fly ash and blast furnace slag (Davidovits, 1989). Unlike OPC, AAMs are synthesized by activation of an aluminosilicate source (fly ash, slag, metakaolin) with alkaline activators. AAMs have attracted a lot of attention in the industry because of its superior mechanical properties, excellent resistance to sulphate attack, low creep and low drying shrinkage compared to OPC.
Besides sustainability, the total amount of costs is also a relevant factor for the construction industry. 3D-printing of concrete removes the need for formwork and enables the industry to create complex shapes as well as optimization of material use. It also provides an opportunity for an automated building process with a minimal amount of labour and material wastage. Combining the use of alkali-activated materials (AAMs) in an innovative and automated 3D-printing process may therefore offer many advantages for the construction industry...