Advancing the Applicability of Recycled Municipal Solid Waste Incineration Bottom Ash as a Cement Substitute in Printable Concrete (2025-02)¶

The sustainability of 3D concrete printing (3DCP) is often compromised by the high cement content required to meet printability standards. This study investigates using recycled municipal solid waste incineration (MSWI) bottom ash as a partial cement substitute to develop concrete with the required rheological and hardening properties for 3DCP, thereby addressing this challenge. The effects of incorporating 10%, 20%, and 30% MSWI bottom ash on the fresh and hardened properties were examined. The shear stress, yield stresses, structuration rate, flowability, setting time, and open time were evaluated in the fresh state. At the hardened state, microstructural evolution and mechanical strengths were analyzed at various curing ages. The findings reveal that 10% and 20% MSWI bottom ash integration results in a denser microstructure, with the formation of hydration products filling the pores, compared to mixes without MSWI bottom ash. The static yield stress within the first 60 mins for R-0, R-10, R-20, and R-30 were 739.5 Pa, 2062 Pa, 1177.2 Pa, and 1036.5 Pa, respectively. Similarly, the dynamic yield stress values within the same resting time and replacement levels were 287.0 Pa, 311.2 Pa, 223.53 Pa, and 178.9 Pa, respectively. The structuration rates for R-0, R-10, R-20, and R-30 were 2.9 Pa/min, 6.6 Pa/min, 7.3 Pa/min, and 4.1 Pa/min, respectively. These results indicate that recycled MSWI bottom ash enhances static and dynamic yield stresses and structuration rates, with the optimal rheological performance observed at a 10% replacement level. The rheological evolution indicates a significant impact of time and MSWI bottom ash content on static yield stress. Notably, the material exhibits considerable strength gains between 45 and 60 mins after mixing. Concrete with 10% MSWI bottom ash shows a 12% increase in compressive strength at 1 day, with no significant changes at 28 and 90 days. These findings suggest MSWI bottom ash is a promising, sustainable alternative for reducing cement content in 3D concrete printing applications.