Concrete production accounts for approximately 8% of global carbon emissions, underscoring the critical need for innovative low-carbon alternatives to support sustainable construction. This review addresses the environmental impact of conventional concrete and its substantial carbon footprint, emphasizing the urgency for transformative technologies. The study examines emerging low-carbon concrete solutions, including the incorporation of supplementary cementitious materials (SCMs), alkali-activated and geopolymer concrete, carbon capture and utilization (CCU), and recycled aggregates, which collectively show potential to reduce emissions by up to 30–50%. The paper also explores advanced mix design strategies aimed at minimizing emissions while maintaining or enhancing structural performance, which could improve durability by 20–25% and decrease lifecycle costs by up to 15%. Challenges to large-scale implementation are critically analyzed, including regulatory obstacles, technical constraints, and market dynamics, with a particular focus on achieving widespread market acceptance within a decade. Future research directions, such as material innovations, enhanced carbon capture methods, and the integration of digital technologies like AI for predictive modelling, are highlighted as pivotal for global adoption. This review demonstrates that the adoption of low-carbon concrete technologies is essential to achieving international climate targets, such as limiting global warming to 1.5 °C while contributing to the construction sector’s sustainability. The findings provide a robust foundation for international research collaboration and policy development aimed at decarbonizing the construction industry.

The fundamentals of engineering and structural properties such as mechanical strength, durability, bond strength, and self-healing behaviour of a genetically-enriched microbe-incorporated construction material have been explored in the present study. The alkaliphilic Bacillus subtilis bacterium is able to survive inside the concrete/mortar matrices for an extended period due to its spore forming ability. The bioremediase-like gene of a thermophilic anaerobic bacterium BKH2 (GenBank accession no. KP231522) was thus transferred to the bacillus strain to develop a true self-healing biological agent. Incorporation of the transformed bacterial cells at different concentrations in the bio-concrete/mortar exhibited higher mechanical strengths and improved durability of the samples in comparison to the normal cement–sand mortar/concretes. Microstructural analyses confirmed the formation of a novel gehlenite (Ca₂Al₂SiO₇) phase besides calcite deposition inside the matrices of the transformed Bacillus subtilis-amended cementitious materials. The gradual development of nano rod-shaped gehlenite composite within the bio-mortar matrices was due to the biochemical activity of the bioremediase-like protein expressed within the incorporated bacterial cells. This development significantly increased the true self-healing property as well as enhanced the mechanical strength of the bio-concrete/mortar material which was sustained for a prolonged period. This study demonstrates a new approach towards the enhancement of structural properties and true self-healing activity by genetically-enriched spore-forming Bacillus sp. with advancement towards sustainable and green construction technology.

A silver–silica nano composite based geopolymer mortar has been developed by simple adsorption of silver in a suitable amount of a colloidal silica suspension for anti-bacterial property development. The silver nanoparticles (3–7 nm) were attached on the surface of 20–50 nm sized silica nanoparticles. The silver–silica nano-composite was characterized by Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and energy dispersive X-ray spectral analysis. Mechanical strength, durability and mechanistic anti-bacterial activity of the silver–silica nano composite modified geopolymer mortar (GM_Ag–Si) were investigated and compared to nano silica modified geopolymer mortar (GM_Si) and control cement mortar (CM). To accesses the anti-microbial efficacy of the samples, 99% mortality for Gram positive and Gram negative bacteria was calculated. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values were determined from batch cultures. The addition of 6% (w/w) of the silver–silica nano composite in the geopolymer mortar cured at ambient temperature shows substantial improvement in mechanical strength, durability and anti-bacterial property. Reactive Oxygen Species (ROS) generation and cell wall rupture as observed from fluorescence microscopy and Field Emission Scanning Electron Microscopy (FESEM) may be possible reasons behind the anti-bacterial efficacy of silver–silica nano composite modified geopolymer mortar.