Effect of drying environment on mechanical properties, internal RH and pore structure of 3D printed concrete. (10th January 2022)

• Record Type: Journal Article
• Authors: Ma, Lei; Zhang, Qing; Jia, Zijian; Liu, Chao; Deng, Zhicong; Zhang, Yamei
• Is Part Of: Construction & building materials. Volume 315(2022)
• Publication Date: 2022-01-10
• Subjects: 3D printing -- Drying -- Mechanical properties -- Pore structure -- Internal RH; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2021.125731
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Compressive and flexural strength of 3DPC decreased by 20%-30% under 60%±5% RH. Severe curing condition (lower RH, higher exposure area, wind) did not show a significant effect on anisotropy of samples cut from printed elements. Strength of printed samples is more sensitive to environment compared with cast samples. Pore shape, number and connectivity of printed samples are different from cast samples. Abstract: 3D printed concrete (3DPC) is fabricated by depositing printable materials without formwork which increases the surface exposed to environmental condition, and by default, eliminates the curing procedure. As a result, moisture evaporation from printed concrete mitigates the hydration of cement and impacts the development of the mechanical properties. In this study, the effects of drying (RH = 60%±5%), wind (3 m/s) and exposed area on the mechanical properties of 3DPC at 20℃±5℃ were investigated. Furtherly, the internal relative humidity evolvement was measured by humidity sensor and the pore distribution was evaluated by X-ray computed tomography. Curing condition were found to have a significant influence on compressive and flexural strength development for samples cut from printed elements and cast samples, but had less significant effect on splitting tensile strength. Furthermore, compared with cast specimens, samples cut from printed elements were more sensitive to curing condition. Evidence on the pore structure seemed to explain the difference: the pore connectivity increased and the pore distribution varied for samples cut from printed elements. We also confirmed the existence of anisotropy for samples cut from printed elements and found that it did not aggravate in drying and wind conditions.