Abstract
Understanding the relationship between the intrinsic characteristics of materials (such as rheological properties and structural build-up) and printability and controlling intrinsic characteristics of materials through additives to achieve excellent printability is vital in digital concrete additive manufacturing. This paper aims at studying the effects of material’s structural build-up on the interlayer bond strength of 3DPC with different time gaps. Structural build-up can indirectly affect the interlayer bond strength by affecting the surface moisture of concrete. Based on the structural build-up of 3DPC, a new parameter, maximum operational time (MOT), is proposed, which can be considered as the limit of time gap to ensure high interlayer bond strength. Slump-retaining polycarboxylate superplasticizer (TS) slightly slows down the physical flocculation rate, but increases the maximum operational time of the cement paste. Nano clay significantly increases the sort-term structural build-up rate and has the function of internal curing and water retaining. Composite with nano-clay and TS can reduce the loss of surface moisture of 3D printed layers, prevent the formation of interface weak layer, and increase the interlayer bond strength between printed layers. This contribution can provide new insight into the design of 3D-printed ink with good extrudability, outstanding buildability, and excellent interlayer bond strength.
Highlights
In recent years, extrusion-based 3D printed cement mortars (3DPC) have attracted extensive attention and research, due to their many benefits to concrete construction, such as eliminating formwork, saving labor costs, reducing wastes and possessing high design-freedom [1,2]
In the process of 3D printing, high structural build-up rate is an important guarantee for multi-layer accumulation [9]
Yield stress and viscosity are two important parameters to characterize the rheological properties of fresh cement paste, which play a significant role in describe the workability of 3DPC and self compacting concrete (SCC) [30]
Summary
Extrusion-based 3D printed cement mortars (3DPC) have attracted extensive attention and research, due to their many benefits to concrete construction, such as eliminating formwork, saving labor costs, reducing wastes and possessing high design-freedom [1,2]. In the case of layer-by-layer printing in 3DPC, optimizing the kinetics of structural build-up is essential to ensure successful printing. Structural build-up is a kinetic process, in which the “strength” of fresh cement paste increases gradually with resting time due to the physical flocculation and chemical hydration reaction. Structural build-up rate has a great influence to the buildability. In the process of 3D printing, high structural build-up rate is an important guarantee for multi-layer accumulation [9]. Excessively high kinetics of structural build-up is not appropriate for the pumping and injection of concrete
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
