Fresh properties of 3D printed mortar with recycled powder. (22nd November 2021) - Hou, Shaodan
Highlights: 3DPM with RP is produced with good extrudability and buildability. RP reduces setting time, improves the strength and Young's modulus of fresh 3DPM. Addition of RP is positive to buildability but is negative to open time for 3DPM. Faster hydration process of RP contributes to the fresh properties of 3DPM. Abstract: In this study, recycled powder (RP) was used to partly replace cement to produce the sustainable 3D printed mortar (3DPM). The properties of fresh 3DPM with RP of different replacement ratio (10%, 20% and 30%) were studied by conventional tests and 3D printer. At first, the flowability, setting time, mechanical property and hydration heat of fresh 3DPM with RP were investigated. Then 3DPM with RP was extruded and built by 3D printer to study the extrudability and buildability. The results show that the incorporation of RP in 3DPM leads to higher flowability losing rate with time, shorter open time, shorter initial and final setting time as well as rapid growth of penetration resistance stress with time. The maximum stress and the Young's modulus of fresh 3DPM grow linearly with time at a lower replacement ratio, while there is a rapid growth when the replacement ratio is higher than 20%. Compared with 3DPM without RP, the maximum stress and Young's modulus of 3DPM with 30% RP are increased 226.5% and 252.2% at 180 min, respectively. The addition of RP enhances the heat evolution rate and hydration heat in 8 h after mixing with water. The well correlation of hydration heat and fresh properties is obtained, which indicates that RP can be used in 3DPM to enhance the early age mechanical properties and buildability. 3DPM with 10%-30% RP has good extrudability and buildability.