Sessions & Events

Early Age Properties of 3D Printed Concrete, Part 2 of 2

Sunday, October 26, 2025  10:30 AM - 12:30 PM, H - Holiday 2

This session highlights recent innovations aimed at minimizing cracking and optimizing the printability of 3D-printed cementitious materials. Presentations explore strategies from both laboratory mix design and field implementation, including shrinkage-reducing admixtures, curing practices, and interlayer bond control. Advances in sustainable, low-clinker printable systems incorporating cellulose nanomaterials are discussed alongside rheological optimization using metakaolin blends. Additionally, in-situ neutron radiography is also introduced as a tool to visualize moisture redistribution during extrusion, offering critical insights into early-age behavior and durability of printed structures.

Learning Objectives:
(1) List key causes of early-age cracking in 3D-printed concrete and how to mitigate them through mix design and field practices;
(2) Examine the role of low/zero-clinker systems and cellulose nanomaterials in improving printability and sustainability;
(3) Assess how rheological testing guides mix optimization for stable, printable concrete;
(4) Develop insights into moisture movement during and after extrusion using neutron imaging and its impact on early-age behavior.

This session has been approved by AIA and ICC for 2 PDHs (0.2 CEUs). Please note: You must attend the live session for the entire duration to receive credit. On-demand sessions do not qualify for PDH/CEU credit.

How to Minimize 3DCP Cracking - From Laboratory to Field

Presented By: Bing Tian
Affiliation: The Quikrete Companies
Description: In the last several years of field practice of 3DCP, cracking has been observed as one of the major defects, which generates a lot of concern about construction quality and building performance. This presentation addresses the cracking issues from two perspectives – lab mix design and field practice. Lab mix design to minimize cracking: • 3DCP mortar vs concrete • Shrinkage compensating techniques -SRA, ettringite formation, pre-hardening and post hardening expansion. etc. • Selection of chemical admixtures – clay, cellulose ether, polymer, fibers, etc. Field practices: • How to deal with ambient condition • Control of the temperature of the 3DCP mix for homogeneous printing • Maintain constant w/c ratio for 3DCP mix to minimize shrinkage • Proper design of printing paths to maintain proper interlayer time and strong bond and prevent cold interlayer joints • Proper curing to prevent skinning and cracking • Proper design of control joints or pre-cutting the wall to release the internal stress

Early-Age Properties of 3D Printed Low/Zero Clinker Cementitious Systems with Cellulose Nanomaterials

Presented By: Mehdi Khanzadeh Moradllo
Affiliation: Temple University
Description: Carbon dioxide (CO2) sequestration using mineral carbonation has been considered as one of the sustainable approaches for addressing the sustainability challenge of cement and concrete production. This study aims at developing 3D printable carbonatable cementitious materials. This is crucial considering the increased attention to implementing concrete 3D in building industry. The fresh and hardened properties and microstructure of the developed mixtures were examined. The benefits of using cellulose nanomaterials were also investigated. A decrease in extrusion pressure was noticed for carbonatable cementitious systems compared to OPC mixtures which can be attributed to the higher “liquid/binder” demand in 3D printable carbonatable systems. The addition of cellulose nanocrystals (CNCs) reduced the extrusion pressure in carbonatable cementitious systems indicating that CNCs can perform as a viscosity-modifying additive in these mixtures. After 14 days of carbonation curing, carbonatable mixtures with CNC show comparable or greater flexural performance compared to the wet-cured OPC system.

Multi-modal Evaluation of the Buildability of 3D Printed Ultra-High Performance Concrete

Presented By: Mohammed Alnaggar
Affiliation: Oak Ridge National Laboratory
Description: Ultra-High Performance Concrete (UHPC) is known for its exceptional strength and durability. While typical UHPC mixes are usually self-consolidating, there are only a few commercially available mixes that exhibit thixotropic behavior. However, UHPC tends to be highly viscous, and when modified for 3D printing, the resulting material not only displays reasonably high yield strength but also increased viscosity. These properties are generally favorable for buildability. However, fully quantifying the rheology and its evolution using standard measurement methods, such as Oscillatory Rheometry, presents significant challenges. Another complication arises from 3D printable UHPC's very high yield stress, which can be mistaken for initial setting. Consequently, traditional testing methods like Vicat testing are unsuitable for 3D-printable UHPCs. This highlights the need to distinguish between material setting and rheological properties when assessing buildability. In this research, multiple commercially available UHPCs were modified for 3D printing, and their early-age properties were evaluated using techniques such as isothermal calorimetry, ultrasonic pulse velocity, static and dynamic flow testing, and squeeze testing. Correlations and insights derived from these results will be presented to propose methods for decoupling setting from rheology. Additionally, this study explores the potential for rapid, on-site testing to inform and enhance the printing process.

In-situ Neutron Radiography Imaging of Cement-Based Material Samples During Extrusion-Based 3D-Printing

Presented By: Luiz Antonio de Siqueira Neto
Affiliation: Oregon State University
Description: This paper presents an in-situ neutron radiography approach to investigate water redistribution in fresh 3D-printed cement-based materials during and immediately after extrusion. A modified extrusion-based 3D printing setup allows for continuous imaging of mortar as it moves through the printer's barrel and nozzle, with high temporal and spatial resolution. Neutron radiographs are processed to extract radial moisture profiles, which reveal flow-induced particle migration effects on the distribution of moisture. The study also captures moisture movement within extruded single-line filament walls between 0-120 min after deposition, examining interactions between filaments and with the surrounding environment. By evaluating the influence of extrusion parameters, mixture compositions, and printed layer configurations on the internal moisture flux of the extruded mortars, this work provides insights into their impact on the spatial distribution of water of fresh 3D-printed materials.