PSI - Issue 64

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2024) 000 – 000

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 64 (2024) 1184–1191

SMAR 2024 – 7th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures Innovations to Improve 3D Concrete Printing of Portland Cement Steel Slag Blended Mortars Zohaib Hassan a, b * , Saim Raza a , Behrouz Shafei c , Mehrdad Mahoutian d , Moslem Shahverdi a,e

a Empa, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland b ETH Zürich, Stefano-Franscini-Platz 1, Zürich 8093, Switzerland c Iowa State University, Ames, IA 50011, United States d Carbicrete, 1730 55e Avenue, Lachine, QC H8T 3J5, Canada e University of Tehran, , 16th Azar Street, Tehran, Tehran, Iran

Abstract This paper identifies typical issues and their remedies during lab-scale 3D printing of Portland cement-steel slag blended mortars. This study used a printer with an accelerator in its feeding system immediately before the extrusion stage. Accelerator dosage can be regulated for such a printer even during printing. However, a higher or lower than optimum dosage may lead to excessive flow or dry surface with a potential risk of cracking in the individual layers. Through the current study, two hollow cylindrical geometry and one hollow square geometry were printed. The print quality was evaluated by investigating various variables, such as considering two superplasticizers with different open times and using constant and variable accelerator dosages during printing. The compatibility of superplasticizers was found to affect the open time and, hence, the print quality with layer shortening and breaking. Changes in accelerator dosage during printing to compensate for the changing rheology were similarly notable, especially in terms of inconsistencies in printed layers. However, the use of a compatible superplasticizer was determined to mitigate both issues. Additionally, shrinkage-reducing admixture was recommended for mortars to avoid cracking due to early-age drying shrinkage. © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers Keywords: 3D concrete printing; quality issues; chemical admixtures; rheology; remedies © 2024 The Authors. Published by Elsevier B.V.

* Corresponding author. Tel.: +41-58-7656537. E-mail address: zohaib.hassan@empa.ch

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers 10.1016/j.prostr.2024.09.165