# Early-Age Shrinkage Monitoring of 3D-Printed Cementitious Mixtures: Comparison of Measuring Techniques and Low-Cost Alternatives

## TL;DR

The study compares various tools for measuring early shrinkage in 3D-printed concrete and finds that low-cost options like smartphones can be effective if properly set up.

## Contribution

The paper introduces low-cost alternatives to expensive optical systems for monitoring early-age shrinkage in 3D-printed concrete.

## Key findings

- DIC provided the earliest and most complete deformation monitoring.
- Laser sensors and LVDTs showed high stability in printed-element testing.
- Low-cost tools like smartphones and GoPro can monitor shrinkage effectively with proper setup.

## Abstract

What are the main findings?
DIC, laser, LVDT, smartphone, and GoPro were evaluated for early-age shrinkage.Aggregate type strongly affects shrinkage and porosity.DIC enabled the earliest and most complete deformation monitoring.Laser sensors and LVDTs showed high stability in printed-element testing.Low-cost tools can monitor early-age shrinkage with good stability.

DIC, laser, LVDT, smartphone, and GoPro were evaluated for early-age shrinkage.

Aggregate type strongly affects shrinkage and porosity.

DIC enabled the earliest and most complete deformation monitoring.

Laser sensors and LVDTs showed high stability in printed-element testing.

Low-cost tools can monitor early-age shrinkage with good stability.

What are the implications of the main findings?
Laser sensors offer high precision without mechanical contact with the sample.Low-cost cameras can substitute commercial DIC if properly stabilized and set.The standard linear shrinkage test is not suitable for early-age shrinkage of 3D-printed concrete.Results support the development of future test standards for 3D-printed concrete.

Laser sensors offer high precision without mechanical contact with the sample.

Low-cost cameras can substitute commercial DIC if properly stabilized and set.

The standard linear shrinkage test is not suitable for early-age shrinkage of 3D-printed concrete.

Results support the development of future test standards for 3D-printed concrete.

Early-age shrinkage in 3D-printed concrete constitutes a critical applied challenge due to the rapid development of deformations and the absence of conventional reinforcement systems. From a scientific standpoint, a clear knowledge gap exists in materials science concerning the reliable quantification of very small, rapidly evolving strains in fresh and early-age cementitious materials produced by additive manufacturing. This study investigates practical and low-cost alternatives to commercial optical systems for monitoring early-age shrinkage in 3D-printed concrete, a key challenge given the rapid deformation of printed elements and their typical lack of reinforcement. The work focuses on identifying both the most precise method for capturing minor, fast-developing strains and affordable tools suitable for laboratories without access to advanced equipment. Three mixtures with different aggregate types were examined to broaden the applicability of the findings and to evaluate how aggregate selection affects fresh properties, hardened performance, and shrinkage behavior. Shrinkage measurements were carried out using a commercial digital image correlation system, which served as the reference method, along with simplified optical setups based on a smartphone camera and a GoPro device. Additional measurements were performed with laser displacement sensors and Linear Variable Differential Transformer LVDT transducers mounted in a dedicated fixture. Results were compared with the standardized linear shrinkage test to assess precision, stability, and the influence of curing conditions. The findings show that early-age shrinkage must be monitored immediately after printing and under controlled environmental conditions. When the results obtained after 12 h of measurement were compared with the values recorded using the commercial reference system, differences of 19%, 13%, 16%, and 14% were observed for the smartphone-based method, the GoPro system, the laser sensors, and the LVDT transducers, respectively.