{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T19:32:09Z","timestamp":1777491129537,"version":"3.51.4"},"reference-count":46,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2023,3,22]],"date-time":"2023-03-22T00:00:00Z","timestamp":1679443200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"European Union","award":["101034352"],"award-info":[{"award-number":["101034352"]}]},{"name":"European Union","award":["293109"],"award-info":[{"award-number":["293109"]}]},{"name":"Academy of Finland via RAMI infrastructure project","award":["101034352"],"award-info":[{"award-number":["101034352"]}]},{"name":"Academy of Finland via RAMI infrastructure project","award":["293109"],"award-info":[{"award-number":["293109"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>As we know, 3DPC is printed layer by layer compared with mold-casting conventional concrete. Pore structure and layer-to-layer interface are two main aspects of the internal structure for 3DPC, which decide 3DPC\u2019s mechanical performance. The layer-to-layer interface caused by printing is specific to 3DPC. The emphasis of this study lies in the layer-to-layer interfaces of 3DPC. The first aim of this study is to quantify the characteristics of the layer-to-layer interface and therefore characterize different aspects of the interfaces. The second aim of this study is to explore how the internal structure of printed concrete influences the mechanical performance of 3DPC. This research set out to design a series of experimental comparisons between 3DPC and casted concrete with the same compositions. Mechanical tests, i.e., compressive stress, ultrasonic Pulse Velocity test, flexural tension, and tension splitting, as well as the Ultrasonic Pulse Velocity test, were performed to check the mechanical performance of 3DPC. Contrary to what has often been expected, the mechanical test results showed the printed concrete has a quality not worse than casted concrete with the same recipe. Meanwhile, the X-ray computed tomography (X-CT) is used to characterize the internal structure, pore shapes, and interfaces of 3DPC. First, the investigation revealed that the lower total porosity and fewer big voids could be the fundamental causes meaning 3DPC has a better mechanical performance than casted concrete. Second, the statistics based on aspect ratio show that the distribution curves follow similar trends, regardless of the printed or casted concrete. Third, this study quantified the depth of the different interfaces for 3DPC. The results suggest that the porosity in an interface varies in a range. The author\u2019s pioneer work has contributed to our present understanding of the interfaces of 3DPC.<\/jats:p>","DOI":"10.3390\/ma16062534","type":"journal-article","created":{"date-parts":[[2023,3,22]],"date-time":"2023-03-22T08:36:16Z","timestamp":1679474176000},"page":"2534","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Investigation of the Internal Structure of Hardened 3D-Printed Concrete by X-CT Scanning and Its Influence on the Mechanical Performance"],"prefix":"10.3390","volume":"16","author":[{"given":"Yanjuan","family":"Chen","sequence":"first","affiliation":[{"name":"Department Materials and Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0241-6838","authenticated-orcid":false,"given":"Jukka","family":"Kuva","sequence":"additional","affiliation":[{"name":"Circular Economy Solutions, Geological Survey of Finland, 02150 Espoo, Finland"}]},{"given":"Ashish","family":"Mohite","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, Aalto University, 02150 Espoo, Finland"},{"name":"Hyperion Robotics Oy, 02630 Espoo, Finland"}]},{"given":"Zhongsen","family":"Li","sequence":"additional","affiliation":[{"name":"Department of Civil Engineering, Aalto University, 02150 Espoo, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6936-828X","authenticated-orcid":false,"given":"Hubert","family":"Rahier","sequence":"additional","affiliation":[{"name":"Department Materials and Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium"}]},{"given":"Fahim","family":"Al-Neshawy","sequence":"additional","affiliation":[{"name":"Department of Civil Engineering, Aalto University, 02150 Espoo, Finland"}]},{"given":"Jiangpeng","family":"Shu","sequence":"additional","affiliation":[{"name":"Department of Civil and Architectural Engineering, Zhejiang University, Hangzhou 310058, China"}]}],"member":"1968","published-online":{"date-parts":[[2023,3,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"121245","DOI":"10.1016\/j.jclepro.2020.121245","article-title":"Comparative economic, environmental and productivity assessment of a concrete bathroom unit fabricated through 3D printing and a precast approach","volume":"261","author":"Weng","year":"2020","journal-title":"J. Clean. Prod."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1016\/j.cemconres.2018.06.001","article-title":"Vision of 3D printing with concrete\u2014Technical, economic and environmental potentials","volume":"112","author":"Lesage","year":"2018","journal-title":"Cem. Concr. Res."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"103855","DOI":"10.1016\/j.cemconcomp.2020.103855","article-title":"Extrusion-based concrete 3D printing from a material perspective: A state-of-the-art review","volume":"115","author":"Mohan","year":"2021","journal-title":"Cem. Concr. Compos."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"104479","DOI":"10.1016\/j.autcon.2022.104479","article-title":"Durability properties of 3D printed concrete (3DPC)","volume":"142","author":"Nodehi","year":"2022","journal-title":"Autom. Constr."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"106800","DOI":"10.1016\/j.cemconres.2022.106800","article-title":"A roadmap for quality control of hardening and hardened printed concrete","volume":"157","author":"Mechtcherine","year":"2022","journal-title":"Cem. Concr. Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"132","DOI":"10.1016\/j.cemconres.2019.02.017","article-title":"Hardened properties of 3D printed concrete: The influence of process parameters on interlayer adhesion","volume":"119","author":"Wolfs","year":"2019","journal-title":"Cem. Concr. Res."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"106078","DOI":"10.1016\/j.cemconres.2020.106078","article-title":"Influence of process parameters on the interlayer bond strength of concrete elements additive manufactured by Shotcrete 3D Printing (SC3DP)","volume":"134","author":"Kloft","year":"2020","journal-title":"Cem. Concr. Res."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"106386","DOI":"10.1016\/j.cemconres.2021.106386","article-title":"Investigation of interlayer adhesion of 3D printable cementitious material from the aspect of printing process","volume":"143","author":"Weng","year":"2021","journal-title":"Cem. Concr. Res."},{"key":"ref_9","unstructured":"Marchment, T., Sanjayan, J.G., Nematollahi, B., and Xia, M. (2019). 3D Concrete Printing Technology, Butterworth-Heinemann."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"107684","DOI":"10.1016\/j.matdes.2019.107684","article-title":"Method of enhancing interlayer bond strength in construction scale 3D printing with mortar by effective bond area amplification","volume":"169","author":"Marchment","year":"2019","journal-title":"Mater. Des."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"106535","DOI":"10.1016\/j.cemconres.2021.106535","article-title":"Interlayer reinforcement of 3D printed concrete by the in-process deposition of U-nails","volume":"148","author":"Wang","year":"2021","journal-title":"Cem. Concr. Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"112","DOI":"10.1016\/j.cemconcomp.2019.03.008","article-title":"A novel method to enhance the interlayer bonding of 3D printing concrete: An experimental and computational investigation","volume":"99","author":"Hosseini","year":"2019","journal-title":"Cem. Concr. Compos."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"118305","DOI":"10.1016\/j.conbuildmat.2020.118305","article-title":"A novel additive mortar leveraging internal curing for enhancing interlayer bonding of cementitious composite for 3D printing","volume":"244","author":"Ma","year":"2020","journal-title":"Constr. Build. Mater."},{"key":"ref_14","unstructured":"Van Der Putten, J., Snoeck, D., and Van Tittelboom, K. (2019). Durable Concrete for Infrastructure under Severe Conditions-Smart Admixtures, Self-Responsiveness and Nano-Additions, Magnel Laboratory for Concrete Research."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"103571","DOI":"10.1016\/j.cemconcomp.2020.103571","article-title":"Interlayer bonding improvement of 3D printed concrete with polymer modified mortar: Experiments and molecular dynamics studies","volume":"110","author":"Wang","year":"2020","journal-title":"Cem. Concr. Compos."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"33","DOI":"10.21809\/rilemtechlett.2019.84","article-title":"Surface modification as a technique to improve inter-layer bonding strength in 3D printed cementitious materials","volume":"4","year":"2019","journal-title":"RILEM Tech. Lett."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"212","DOI":"10.1016\/j.autcon.2017.08.019","article-title":"Effects of interlocking on interlayer adhesion and strength of structures in 3D printing of concrete","volume":"83","author":"Zareiyan","year":"2017","journal-title":"Autom. Constr."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"586","DOI":"10.1016\/j.conbuildmat.2019.01.235","article-title":"Effects of layer-interface properties on mechanical performance of concrete elements produced by extrusion-based 3D-printing","volume":"205","author":"Nerella","year":"2019","journal-title":"Constr. Build. Mater."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"125","DOI":"10.1016\/j.conbuildmat.2018.05.202","article-title":"3D-printed steel reinforcement for digital concrete construction\u2013Manufacture, mechanical properties and bond behaviour","volume":"179","author":"Mechtcherine","year":"2018","journal-title":"Constr. Build. Mater."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"125731","DOI":"10.1016\/j.conbuildmat.2021.125731","article-title":"Effect of drying environment on mechanical properties, internal RH and pore structure of 3D printed concrete","volume":"315","author":"Ma","year":"2022","journal-title":"Constr. Build. Mater."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"121745","DOI":"10.1016\/j.conbuildmat.2020.121745","article-title":"A review of 3D printed concrete: Performance requirements, testing measurements and mix design","volume":"273","author":"Hou","year":"2021","journal-title":"Constr. Build. Mater."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"126743","DOI":"10.1016\/j.conbuildmat.2022.126743","article-title":"A mechanistic evaluation relating microstructural morphology to a modified Mohr-Griffith compression-shear constitutive model for 3D printed concrete","volume":"325","author":"Bester","year":"2022","journal-title":"Constr. Build. Mater."},{"key":"ref_23","unstructured":"Sonebi, M., Amziane, S., and Perrot, A. (2019). 3D Printing of Concrete, ISTE."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"120094","DOI":"10.1016\/j.conbuildmat.2020.120094","article-title":"Effect of printing parameters on interlayer bond strength of 3D printed limestone-calcined clay-based cementitious materials: An experimental and numerical study","volume":"262","author":"Chen","year":"2020","journal-title":"Constr. Build. Mater."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"126740","DOI":"10.1016\/j.conbuildmat.2022.126740","article-title":"Effects of extrusion parameters on properties of 3D printing concrete with coarse aggregates","volume":"325","author":"Ji","year":"2022","journal-title":"Constr. Build. Mater."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"125809","DOI":"10.1016\/j.conbuildmat.2021.125809","article-title":"The relationship between the rheological behavior and interlayer bonding properties of 3D printing cementitious materials with the addition of attapulgite","volume":"316","author":"Yao","year":"2022","journal-title":"Constr. Build. Mater."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"127496","DOI":"10.1016\/j.conbuildmat.2022.127496","article-title":"Study on the mechanical properties of 3D printing concrete layers and the mechanism of influence of printing parameters","volume":"335","author":"Huang","year":"2022","journal-title":"Constr. Build. Mater."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"109619","DOI":"10.1016\/j.compositesb.2022.109619","article-title":"Effect of sulphoaluminate cement on fresh and hardened properties of 3D printing foamed concrete","volume":"232","author":"Liu","year":"2022","journal-title":"Compos. Part B Eng."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"106040","DOI":"10.1016\/j.cemconres.2020.106040","article-title":"Improving printability of limestone-calcined clay-based cementitious materials by using viscosity-modifying admixture","volume":"132","author":"Chen","year":"2020","journal-title":"Cem. Concr. Res."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"106968","DOI":"10.1016\/j.compositesb.2019.106968","article-title":"Printability region for 3D concrete printing using slump and slump flow test","volume":"174","author":"Tay","year":"2019","journal-title":"Compos. Part B Eng."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1221","DOI":"10.1617\/s11527-012-9828-z","article-title":"Mix design and fresh properties for high-performance printing concrete","volume":"45","author":"Le","year":"2012","journal-title":"Mater. Struct."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"558","DOI":"10.1016\/j.cemconres.2011.12.003","article-title":"Hardened properties of high-performance printing concrete","volume":"42","author":"Le","year":"2012","journal-title":"Cem. Concr. Res."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"106559","DOI":"10.1016\/j.cemconres.2021.106559","article-title":"Modelling the interlayer bond strength of 3D printed concrete with surface moisture","volume":"150","author":"Moelich","year":"2021","journal-title":"Cem. Concr. Res."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"119587","DOI":"10.1016\/j.conbuildmat.2020.119587","article-title":"Neutron radiography to study the water ingress via the interlayer of 3D printed cementitious materials for continuous layering","volume":"258","author":"Azima","year":"2020","journal-title":"Constr. Build. Mater."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"150","DOI":"10.1016\/j.cemconcomp.2019.02.008","article-title":"Investigation of concrete workability through characterization of aggregate gradation in hardened concrete using X-ray computed tomography","volume":"98","author":"Sokhansefat","year":"2019","journal-title":"Cem. Concr. Compos."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1016\/j.cemconcomp.2012.06.001","article-title":"Density mapping of hardened cement paste using ptychographic X-ray computed tomography","volume":"36","author":"Trtik","year":"2013","journal-title":"Cem. Concr. Compos."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"360","DOI":"10.1016\/j.cemconres.2006.10.012","article-title":"3D experimental investigation of the microstructure of cement pastes using synchrotron X-ray microtomography (\u03bcCT)","volume":"37","author":"Gallucci","year":"2007","journal-title":"Cem. Concr. Res."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"229","DOI":"10.1016\/j.fuel.2013.07.037","article-title":"3D chemical segmentation of fly ash particles with X-ray computed tomography and electron probe microanalysis","volume":"116","author":"Hu","year":"2014","journal-title":"Fuel"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"62","DOI":"10.1109\/TSMC.1979.4310076","article-title":"A threshold selection method from gray-level histograms","volume":"9","author":"Otsu","year":"1979","journal-title":"IEEE Trans. Syst. Man Cybern."},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Markoe, A. (2006). Analytic Tomography, Cambridge University Press.","DOI":"10.1017\/CBO9780511530012"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"74","DOI":"10.1504\/IJSTRUCTE.2017.081672","article-title":"Visual inspection and non-destructive tests-based rating method for concrete bridges","volume":"8","author":"Pushpakumara","year":"2017","journal-title":"Int. J. Struct. Eng."},{"key":"ref_42","unstructured":"Al-Neshawy, F., and Hassan, A. (2021). Defining Concrete Compressive Strength by Combining the Results of Different NDT Methods, Aalto University."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.cemconcomp.2018.03.017","article-title":"A self-reinforced cementitious composite for building-scale 3D printing","volume":"90","author":"Soltan","year":"2018","journal-title":"Cem. Concr. Compos."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"262","DOI":"10.1016\/j.powtec.2015.12.029","article-title":"3D quantitative shape analysis on form, roundness, and compactness with \u03bcCT","volume":"291","author":"Zhao","year":"2016","journal-title":"Powder Technol."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"1533","DOI":"10.1007\/s11440-019-00845-3","article-title":"Prediction of 3D size and shape descriptors of irregular granular particles from projected 2D images","volume":"15","author":"Su","year":"2020","journal-title":"Acta Geotech."},{"key":"ref_46","unstructured":"Strzelecki, P.J., Fheed, A., and Raczy\u0144ski, P. (2020). AIP Conference Proceedings, AIP Publishing LLC."}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/16\/6\/2534\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T19:00:46Z","timestamp":1760122846000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/16\/6\/2534"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,3,22]]},"references-count":46,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2023,3]]}},"alternative-id":["ma16062534"],"URL":"https:\/\/doi.org\/10.3390\/ma16062534","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,3,22]]}}}