Enhancing 3D Printed Concrete Through Waste Fly Ash (2025-06)¶

The significance of replacing sand with waste fly ash (WFA) in the mix design of concrete for 3D printing applications extends beyond just one or two attributes; it encompasses environmental, economic, and structural considerations. WFA, recognized for its pozzolanic properties, actively participates in the chemical reactions during cement hydration. This interaction leads to the formation of additional cementitious materials, which contribute positively to the concrete’s durability and compressive strength. WFA reduces the dependence on naturally occurring sand, conserves natural resources, and mitigates ecological disturbances caused by sand extraction. The inclusion of WFA in concrete can reduce permeability and increase the solidified material’s long-term strength. WFA imparts enhanced qualities to printed concrete, such as reduced permeability and improved long-term strength, which are critical for the structure’s durability and lifespan. As 3D printing rapidly constructs structures layer by layer, early-age strength is particularly crucial to ensuring that the structure can support itself during the printing process. This is where admixtures come into play, moderating factors like setting time and aiding in achieving the desired rheological properties that ensure the printability of concrete. Admixtures serve to fine-tune the mix design, offering control over the setting time, which, if delayed, can hinder the printing process’s speed and efficiency. They also enhance the bonding between layers and improve overall workability, which is essential for achieving the dimensional accuracy and fidelity required by complex 3D-printed designs. The measurement of the early-age compressive strength of concrete offers a window into the material’s initial phase of solidification and the rate at which it gains strength. This property is a critical indicator of the concrete’s ability to reach a state of rigidity capable of withstanding loads, which is particularly vital in the context of 3D-printed structures where the printing process is continuous and rapid. The integrity of each successive layer depends on the sturdy foundation provided by the preceding segment. Higher early-age strength ensures that the construction process can proceed promptly without the risk of structural failure or deformity. The 28-day strength is regarded as the benchmark for assessing the excellence and maximum load-carrying capability of the concrete. In the context of 3D printing, it is crucial to verify that the layered structure will satisfy the necessary service requirements and structural standards, which frequently depend on the 28-day strength values.