Automatic construction systems have become the focus of the construction industry and research projects worldwide. Numerous technologies involving 3D printing (3DP) of concrete elements have been developed, and their application in construction projects has been growing. The 3DP in concrete construction is increasing due to its freedom in geometry, rapidness, formwork-less printing, low waste generation, eco-friendliness, cost-saving nature, and safety. Development of 3DP is not only limited to the earth but also gaining attention for building habitats in space. This study aims to present the technical, socio-economical, and environmental aspects related to 3DP of concrete structures for a systematic summation of the technology, guidelines, applications, challenges, and prospects of future research and market in the construction industry. This comprehensive review shows that challenges involved in 3D concrete printing should be analyzed further by researchers to enhance mechanical performance, durability, and sustainability and establish appropriate standard guidelines for printing structures.

Every year, the world is producing around 100 million tons of waste glass (WG), the majority of them are going to landfills that create massive environmental problems. One approach to solve this problem is to transform waste glass into construction materials. Glass is recyclable; however, the melting temperature of the glass is highly dependent on its colour that requires sorting before recycling. To overcome this challenge, many researchers and end-users are using broken glass in concrete either as a binder or aggregates. While significant investigations have done in this area, however, the outcomes of these studies are scattered, and difficult to reach a firm conclusion about the effectiveness of WG in concrete. In this study, the roles of WG and its impact on microstructural and durability properties for both cement and geopolymer concrete are critically reviewed. This review reveals that the amorphous silica in WG effectively participate to the hydration and geopolymerization process and improve concrete microstructural properties. This behaviour of WG help to produce durable concrete against shrinkage, chemical attack, freeze-thaw action, electrical and thermal insulation properties. The optimum replacement volume of binders or natural aggregates and particle size of WG need to be selected carefully to minimise the possible alkali-silica reaction. This review discusses a wide range of parameters for durability properties and challenges associated with WG concrete, which provides necessary guidelines for best practice with future research directions.