Experimental assessment of rheological behavior and environmental impact of low-carbon cementitious paste with fly ash and GGBS

The present study investigates the potential of widely used supplementary cementitious materials (SCMs) such as fly ash (FA) and ground granulated blast furnace slag (GGBS) to improve the rheological and environmental performance of low-carbon cementitious pastes. Three binders consisting of 100% OPC, 25% FA, and 70% GGBS were tested at water-to-binder ratios of 0.4 and 0.45. The dynamic shear rheometer was employed to analyze shear-thickening behavior of various cementitious suspensions. Subsequently, the environmental life cycle assessment (LCA) was conducted within a “cradle-to-gate” framework, evaluating six environmental impact categories and proposing a novel approach to converting these impacts into a single environmental cost (USD). The results revealed that OPC suspensions exhibit the earliest and most pronounced shear-thickening onset, while 70% GGBS suspensions reduce global warming potential but increase acidification impact. In contrast, 25% FA suspensions minimize acidification impact. Moreover, the rheological behavior is significantly influenced by solid volume fraction (SVF) and particle morphology; 70% GGBS pastes demonstrate the highest yield stress (140 Pa) and plastic viscosity (1.61 Pa. s) at a w/b ratio of 0.4, attributed to their angular particle shape. The environmental cost of suspensions (100% OPC) is estimated at $13.92/m3, with OPC being the primary contributor. The findings highlight the potential of SCMs to enhance performance and reduce environmental impacts, supporting greater use of FA and GGBS for sustainable, low-carbon infrastructure development. Future research should focus on optimizing the combined use and dosage of FA and GGBS in low-carbon cementitious pastes to achieve a more effective balance among rheological performance, environmental sustainability, and economic viability. Equally important is the need to extend the assessment framework beyond the present scope by incorporating long-term performance and durability assessment, broader system boundaries, and more rigorous environmental cost evaluation should be incorporated to enable the development of robust and sustainable cementitious systems.Implications: India has set an ambitious goal of achieving carbon neutrality by 2070. In the coming years, a substantial increase in building construction is anticipated to accommodate the country’s growing population. However, this expansion threatens to hinder progress toward national sustainable development goals (SDGs) and commitments to the Paris Climate Agreement. Indian thermal power plants and steel plants produce substantial amounts of fly ash and slag, which are solid waste byproducts. To mitigate the environmental impact and reduce cement consumption, it is essential to utilize these materials in construction. By incorporating fly ash and slag as cement replacement materials, we can significantly decrease the carbon footprint of the construction industry, contributing to both sustainability and resource efficiency. The paper uniquely integrates the rheological properties of cementitious suspensions with a comprehensive environmental assessment, offering a dual perspective on performance and sustainability. A novel methodology has been proposed to consolidate environmental impacts into a single environmental cost, expressed in US dollars, providing a practical decision-making tool.