The layer interface, which is vital for the performance and longevity of 3D printed cement-based materials (3DPCM), is very sensitive to the environmental conditions because of the lack of formwork. Nevertheless, the current limited understanding of how temperature affects the layer interface has restricted the application of 3D printing in different construction scenarios. Here, we revealed the effects of temperature on the multi-scale phase distribution features of the layer interface through mercury intrusion porosimetry, X-ray computed tomography, nanoindentation and scanning electron microscopy with energy dispersive spectroscopy techniques. Additionally, the interlayer bond strength of 3DPCM was evaluated via the splitting tensile test. Small amplitude oscillation, surface roughness and isothermal calorimetry measurements were employed for an in-depth analysis of the mechanisms. Results indicate that an increase in temperature post-printing reduces the discrepancies in aggregate volume fraction between the layer interface and bulk matrix due to the increasing structuration rate and the amount of cement paste at the interface due to the reduced settlement of aggregates. The porosity difference between the layer interface and bulk matrix decreased with increasing temperature due to the pore size refinement by faster filling with hydrates. In addition, a more concentrated distribution of atomic ratios and elastic modulus of hydrates were observed at the layer interface of 3DPCM hardened at higher temperatures. Increased curing temperature improves the interlayer bond strength of 3DPCM owing to the enhanced aggregate interlocking, reduced porosity and improved high-density CSH content.

中文翻译：

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暴露于打印后温度干扰的 3D 打印水泥基材料的层界面特性和附着力


层界面对 3D 打印水泥基材料 （3DPCM） 的性能和使用寿命至关重要，但由于没有模板，因此对环境条件非常敏感。然而，目前对温度如何影响层界面的有限理解限制了 3D 打印在不同施工场景中的应用。在这里，我们通过汞侵入孔隙度测定、X 射线计算机断层扫描、纳米压痕和利用能量色散光谱技术的扫描电子显微镜揭示了温度对层界面多尺度相位分布特征的影响。此外，通过劈裂拉伸试验评估了 3DPCM 的层间粘合强度。采用小振幅振荡、表面粗糙度和等温量热法测量对机制进行深入分析。结果表明，由于结构速率增加，打印后温度的升高减少了层界面和块状基质之间骨料体积分数的差异，并且由于骨料沉降减少，界面处的水泥浆量增加。层界面和体基体之间的孔隙率差异随着温度的升高而减小，这是由于通过更快地填充水合物来细化孔径。此外，在较高温度下硬化的 3DPCM 的层界面处观察到水合物的原子比和弹性模量分布更加集中。由于增强的骨料互锁、减少孔隙率和提高高密度 CSH 含量，固化温度的提高提高了 3DPCM 的层间粘合强度。