Statistical approach for design of a zero Portland cement concrete and evaluation of their decarbonisation potential

Portland cement (PC) constitutes only 12 to 15% of concrete but is responsible for approximately 90% of embodied carbon (EC). This is the reason why most concrete decarbonisation strategies consider the partial or full replacement of cement as the focal point. The supplementary cementitious materials (SCMs) are commonly used for the partial replacement of PC. Australian Technical Infrastructure Committee (ATIC) specifications compliant level of replacement of PC with SCMs in a binary or ternary blend may reduce EC of concrete by up to 59%. Zero Portland cement (ZPC) concrete, also known as PC-free concrete, is considered as a sustainable alternative to traditional concrete that minimizes or eliminates the use of PC reducing embodied carbon as well as the process emission. ZPC concrete uses alternative binders such as geopolymer (SCMs in conjunction with alkali activators), sulphur, lime calcinated clay (LC3) etc. instead of PC. These binders produce equivalent or better performing concrete with potentially lower EC. The geopolymer concrete (GC) is produced by activating SCMs with alkali activators and sulphur concrete (SC) is produced by mixing sulphur with pre-heated aggregates. This research paper evaluates the potential applications of geopolymer concrete and sulphur concrete in construction as low carbon concrete. This paper presents a statistical approach for the preliminary design of a fit for purpose (concrete complying with mechanical property and durability performance requirements) geopolymer concrete and sulphur concrete. This research paper also presents a new approach for evaluating various types of concretes designed for various service life and recyclability. A multi-dimensional performance-carbon indicator ‘Decarbonization Index (DI)’ has been developed which integrates embodied carbon, compressive strength, service life and recyclability potential of a concrete mix in place of EC being used currently. DI may be used as a simplified decision-making tool for selecting the lowest carbon fit for purpose concrete giving due consideration to its upcycling potential.