11 Aug 2025

3D Printing of Ultra-High-Performance Concrete: Shape Stability for Various Printing Systems

Abstract: Attention is on concrete 3D printing for its potential in structure optimization, life-cycle extension, emission reduction, and cost savings. Previous studies tailor a mix to a specific printing system and evaluate printability based on measurements of pumpability, extrudability, and buildability. For this investigation, an experimental program was conducted using various printing systems on a nano-modified UHPC mix. A medium-scale gantry and a large-scale ABB robotic arm were utilized, piston-type extruder and an auger system were employed, various nozzles, including circular and rectangular designs, were tested, and a cavity and Thom-Katt pump were used. Results indicated the shape stability of the UHPC mix is influenced by the printing system. Furthermore, the use of a circular nozzle demonstrated different shape stabilities when the extrusion system was changed from a piston-type extruder to an auger system. Additionally, the method of material pumping to the extrusion system was found to be critical for shape stability of printed layers. The mix failed to maintain its shape post-extrusion when using the cavity pump, which was attributed to higher strain rates imposed on material during the pumping process. This issue was not observed when the piston-type pump was used.

29 Sep 2023

Development and Characterization of Ultra-High-Performance Concrete for the Rehabilitation of Navigation Lock Structures

Abstract: This report details the history of vertical lock wall repairs and the development and laboratory characterization of an ultra-high-performance concrete (UHPC) using locally sourced materials for improved durability of lock walls subjected to impact and abrasion from navigational vessels. This UHPC, referred to as Lock-Tuf, has been designed for use in a precast environment with ambient curing methods and serves as a material proof-of-concept for future lock wall rehabilitations. Mechanical properties such as unconfined compressive strength, flexural response, tensile capacity, impact resistance, and abrasion resistance have been quantified experimentally.

4 May 2021

Laboratory characterization of Cor-Tuf Baseline and UHPC-S

Abstract: This experimental effort is part of a larger program entitled Development of Ultra-High-Performance Concrete Tools and Design Guidelines. This program operates in accordance with an agreement concerning combating terrorism research and development between the United States of America Department of Defense and the Republic of Singapore Ministry of Defence. The objective of the program is to develop a better understanding of the potential benefits that may be achieved from the application of ultra-high-performance concrete (UHPC) materials for protective structures. The specific effort detailed in this report will provide insight into laboratory-scale mechanical properties of Cor-Tuf and a proprietary material termed UHPC-Singapore (UHPC-S).