In this paper the effects of the addition of a paraffin phase change material on the strength and printability of 3D printed concrete are studied. Phase change materials are latent heat storing materials, which garner and release large amounts of energy as they change phase. The addition of phase change materials to concrete produces a composite material with maximised latent and sensible heat storage capacity. Used in buildings, this composite material has the ability to minimise unwanted heat transfer across the building envelope. An existing mix design (RBA-3DPC), in which 64% of the natural aggregate in a 3D printable concrete (3DPC) had been replaced with recycled brick aggregate, is adjusted by adding phase change material to the pores of the recycled brick aggregate by vacuum impregnation, creating PCM-3DPC. Rheological characterisation tests are performed on reference mix designs (3DPC and RBA-3DPC) and the PCM-3DPC mix design, and used in a buildability model to validate the number of printable layers. Mechanical characterisation tests including cube strength tests, direct tensile tests and uniaxial compressive tests are performed on cast and printed specimens of the mix designs. There is no existing research on the effects of the combined addition of recycled brick aggregate and phase change material in 3D printed concrete. It is concluded that the PCM-3DPC has the highest number of printable layers predicted by the model and realised by a cylindrical column print and overall, PCM-3DPC has greater strength compared to RBA-3DPC, and lower strength compared to 3DPC. The PCM-3DPC exceeds the RBA-3DPC interlayer tensile strength by 6%, intralayer compressive strength by 43% and interlayer compressive strength by 9%, and subceeds the 3DPC interlayer tensile strength by 15% and interlayer compressive strength by 13%.

Due to the substantial contribution of the construction industry to greenhouse gas emissions, there exists a pressing need for the development and adoption of sustainable alternatives. In this context, hempcrete has emerged as a promising alternative in the pursuit of sustainable construction practices. This paper presents a comprehensive review of the existing research landscape surrounding hempcrete as a sustainable building material. The review explores the primary materials utilised in hempcrete, followed by an analysis of the opportunities and limitations associated with the material. Furthermore, the paper investigates diverse construction techniques and practical applications, binders, mix designs, as well as the properties of hempcrete spanning from fresh-state characteristics to the mechanical, durability, thermal, and acoustic properties of the material. Moreover, the environmental sustainability as well as the cost of hempcrete construction are investigated. Upon analysis of the research presented in this review paper, it becomes apparent that hempcrete demonstrates noteworthy potential as a sustainable solution in the construction sector, emphasising its role in reducing the environmental impacts brought about by the construction industry. This review paper presents the findings of the current research landscape of hempcrete and provides insights for future research endeavours aimed at optimising the performance of hempcrete.