Economic growth and rapid urbanization have resulted in the increase in demand for infrastructure development. To meet this ever increasing demand, conventional construction materials such as concrete are used, which requires an energy intensive process that in turn impacts the environment adversely. Ordinary Portland Cement, being the dominant binder in the industry, contributes around 8% of worldwide annual carbon emissions, and this is expected to reach around 20% by 2050. Population growth has resulted in the significant increase in agro-industrial waste generation during recent years. Inadequate waste management raises a number of environmental concerns. With the growing economy and rising living standards, global raw material consumption is expected to double by 2060. The reutilization of waste materials will aid in their management, while conserving the available resources. Alkali-activated materials (AAM) have recently been introduced as an eco-friendly alternative to conventional binders with fewer environmental impacts. AAM reduce the need for Ordinary Portland Cement (OPC) by substituting it with supplementary cementitious materials (SCM), and therefore, reducing the amount of subsequent carbon emissions. Alkali activation is a complex chemical process between the precursors (alumino-silicate materials) and their dissolution in the activators. Different materials react to alkali activators in different ways depending on their properties. The current study aims to provide a critical review of potential agro-industrial wastes on the fresh and hardened properties of alkali-activated concrete (AAC). To understand the design and development of AAC, influencing the parameters such as the molarity of NaOH, alkali activators, and the ratio of the activators have been discussed in detail. The curing regime and its effect on the behavior of alkali-activated concrete are mentioned. The different admixtures used to regulate the properties of AAC are highlighted. AAC exhibited optimized embodied energy, operational energy, life cycle cost, CO₂ emission, and raw material consumption rates than the conventional concrete did. However, these results varied based on the precursors used in them. This paper focuses on the design and development of AAC, and it should be viewed as an important contribution towards the adoption of AAC in practical applications. The study presents the potential of AAM as a net zero binder in the making of sustainable concrete with enhanced properties.

The construction industry has experienced phenomenal growth because of technological advancements in the past couple of decades. Prefabrication constitutes a sizeable share of this industry and is being adopted all over the world. The method of casting construction elements in a controlled environment and assembling them on-site has revolutionised the industry. Research on various aspects of the technology is ongoing around the world, and an impressive number of articles have been published. However, the prefab technology, materials used, and terminology have varied across locations, which may have hindered the method’s wider acceptability. By evaluating technical articles published between 1991 and 2022, this report analyses the present body of knowledge regarding prefab technology, its evolution, sustainability, and stakeholder views. This technology effectively contributes around 40% in time saving, 27% in cost reduction, 30% in reduced carbon emissions, and 84% in on-site wastage reduction. It also increases quality, gives a dependable alternative for meeting mass construction targets, is energy efficient, and provides environmentally conscious options. This paper contributes to the body of knowledge by providing a snapshot of the prefab industry spanning three decades, detailing a wide range of factors affecting the industry.

Under the India “Housing for all” scheme, 20 million urban houses have to be constructed by 2022, which requires the rate of construction to be around 8000 houses/day. Previous results by the team show that present design methods for affordable buildings and structures in India need improvement. The challenges are the disposal of solid waste generated from agro-industrial activities and the energy peak demand in extremely hot and cold seasons. The development of bio-based urban infrastructure which can adapt to the climatic conditions has been proposed. Inclusion of sustainable materials such as agro-industrial by-products and insulation materials has resulted in effective environmental sustainability and climate change adaptability. Precast components are highlighted as a suitable solution for this purpose as well as to fulfil the need of mass housing. India has a lesser record in implementing this prefab technology when compared to a global view. For the first time, a novel and sustainable prefab housing solution is tested for scale-up using industrial waste of co-fired blended ash (CBA) and the results are presented here. A model house of real scale measuring 3 × 3 × 3 m³ was considered as a base case and is compared with 17 other combinations of model house with varying alignment of prefab panels. Comparison was made with commercially available fly ash brick and CBA brick with a conventional roof slab. A simulation study was conducted regarding cost and energy analysis for all the 18 cases. Various brick and panel compositions with CBA for housing were tried and the superior composition was selected. Similarly, 18 model houses of real scale were simulated, with different combinations of walls made of bricks or panels and different building orientations, to check the impact on energy peak cooling and cost. Results show that peak cooling load can be reduced by six times with bio-based prefab panels. Prefab construction can be considered for mass housing ranging above 100 housing units, each consisting of an area of 25 m².

Rapid construction with an energy-efficient approach is a major challenge in the present construction industry. Cement, a carbon-intensive material, is mainly used in the construction industry and hence increases the sector’s carbon footprint on the environment. The current review focuses on the study of 3D concrete printing (3DCP), in which cement is partially replaced with industrial byproducts such as ground granulated blast furnace slag (GGBS), fly ash, and silica fume. Walling material is primarily targeted in 3DCP. There is a need to include energy efficiency to achieve a thermally comfortable environment. The life cycle assessment (LCA) of concrete is studied to discover the potential conflicts affecting the environment. The sand-to-binder ratio is pivotal in determining the performance of concrete. The content of the supplements is decided based on this factor. The rheological, physical, and mechanical properties of 3DCP are studied further and analysed. GGBS demonstrates better performance in the compressive and flexure strength of concrete. The usage of fly ash and silica fume has reduced the thermal conductivity of the material, whereas GGBS has increased it. An LCA study shows that 3DCP can be made sustainable with the use of these supplementary cementitious materials.

The construction world has changed day by day and is becoming more digitalized by introducing new technologies. Three-dimensional concrete printing (3DCP) is one such technology that has automated building process along with several benefits such as reduced material waste, reduced human hazard, and time savings. Traditionally, this technique utilizes cement to construct numerous structures, resulting in a significant carbon footprint and negative environmental impact. There is a need to find alternate solutions to reduce cement consumption. Alkali activation technology has replaced cement completely. The scope of development of alkali-activated 3D printable concrete utilizing agro-industrial byproducts is presented in this study. A review of the fresh and hardened properties of alkali-activated 3D printable concrete was the primary objective. The change in properties of 3D concrete mixes with the variation of additives that influence the ultimate strength parameters is presented. This study explores the curing conditions and in-depth behavior of uses of 3DCP in the construction industry. The environmental benefits over conventional concreting technology are presented. As per previous studies, the optimum mix composition per cubic meter concrete is 600–700 kg/m³ of binder content, 450 kg/m³ of alkali activator solution, and 600–800 kg/m³ of fine aggregate content. This study contributes to the making of 3D printable alkali-activated concrete.

India is in need of rapid construction technology with sustainability and environmentally friendly aspects. Prefabrication is a well-known technique that lowers carbon emissions and reduces environmental impacts. Life cycle assessment (LCA) evaluates these impacts of developed product/process. A new-age construction product was designed from a locally available agro-industrial waste called co-fired ash (CFA). Expanded polystyrene beads, fly ash, and crushed sand were also used in designing lightweight (LW) sustainable prefabricated panels. The effect of incorporating sustainable alternates into the mix designs is to be studied. An experimental small-scale model house was erected and LCA for the same was carried out with cradle-to-site approach. Based on the inventory, the environmental impact was assessed for four different indicators: acidification potential (AP), eutrophication potential (EP), global warming potential (GWP), and ozone depletion potential (ODP) were evaluated. Carbon emissions of the respective CFA-based concrete and LW prefabricated mix were found to be 0.162 kgCO₂e/kg and 0.268 kgCO₂e/kg, respectively. The impact of energy required during production, transport, and indirect emissions were found to contribute 3%, 3%, and 94%, respectively, to the proposed prefabricated system. Comprehensively, the phase involving mixing of LW mix contributed majorly towards all the impact indicators followed by mould preparation and material transport. The presented data helps the academia to quantify and recognise the possibilities to enhance their products’ performance.