Feasible supplementary cementitious materials for sustainable and advanced 3D concrete printing

Abstract Three-dimensional concrete printing (3DCP) is emerging as a sustainable technology because of automation and material efficiency. However, high Portland cement content compromises its environmental impact. Although using supplementary cementitious materials (SCMs) is a promising pathway to improve the environmental sustainability of printable mixtures, their technical and environmental viability is still a challenge. A systematic literature review was performed to understand the feasibility of standard and alternative SCMs as partial Portland cement replacements in 3DCP by considering technical feasibility, legal barriers, fresh state behaviour, and hardened performance. Standard SCMs have well-established standards and treatment processes, but their local availability and supply issues limit their use. Although SCMs from alternative sources, such as waste and by-products, can enhance resource efficiency and sustainability, their feasibility is limited by physical and chemical properties, which impact fresh and hardened performance. Thus, ground granulated blast furnace slag, fly ash, limestone powder, ornamental stone waste, and waste glass powder improve flowability, pumpability, and extrudability, while silica fume, calcined clay, metakaolin, burnt oil shale, construction and demolition waste powders, waste brick powder, and municipal solid waste are generally responsible for increasing the buildability and shape retention. Hence, ternary binders with Portland cement and two SCMs are commonly used to optimise fresh properties and achieve the desirable printability and hardened performance. The literature review indicates that combining SCMs with complementary rheological effects allows for achieving a balance between flowability and shape retention during the printing process. However, future life cycle assessments of printable mixtures with sensitivity analyses, including transport distance, treatment, and valorisation strategies, are required to boost the incorporation of alternative SCMs in printable mixtures.