This study examines the effect of the material characteristics of superabsorbent polymers (SAPs) on the printability and interlayer bond strength of 3D printing concrete. Three types of SAP, including two acrylamide-co-acrylic polymers with coarse and fine particle sizes (S1 and S2) and an acrylic copolymer (S3), were employed. The investigated mortar mixtures had a fixed initial mini-slump flow of 195 ± 10 mm and yield stress of 290 ± 25 Pa. The fluidity of SAP-incorporated mortars was maintained by either adjusting the superplasticizer dosage or increasing the water content. Test results indicate that particle flocculation is dependent on SAP absorption kinetics shortly after the end of mixing. The use of S1 and S2 SAPs exhibiting high retention ability enhanced thixotropy, whereas the S3 SAP with rapid desorption reduced thixotropy. The S2 SAP improved the bridging effect of nucleation at early age due to its finer size, leading to a significant increase in the structuration rate at 30 min. Pull-out strength test and splitting tensile strength test were used to investigate the interlayer bond strength. The S1 SAP was the most significant in maintaining a higher internal relative humidity (IRH), thus resulting in higher 28-d interlayer bond strength, while the S2 SAP exhibited an intermediate ability to maintain elevated IRH, thus resulting in higher increase in 7-d interlayer bond strength.

中文翻译：

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高吸水性聚合物的吸收动力学对3D打印混凝土可打印性和层间粘结的影响


本研究探讨了高吸水性聚合物 (SAP) 的材料特性对 3D 打印混凝土的可打印性和层间粘合强度的影响。采用三种类型的 SAP，包括两种具有粗粒度和细粒度的丙烯酰胺-丙烯酸聚合物（S1 和 S2）和丙烯酸共聚物（S3）。所研究的砂浆混合物具有 195 ± 10 mm 的固定初始微型坍落度和 290 ± 25 Pa 的屈服应力。通过调整高效减水剂用量或增加含水量来维持 SAP 掺入砂浆的流动性。测试结果表明，颗粒絮凝取决于混合结束后不久的 SAP 吸收动力学。使用表现出高保留能力的 S1 和 S2 SAP 增强了触变性，而具有快速解吸能力的 S3 SAP 降低了触变性。 S2 SAP 由于其尺寸更细，改善了早期成核的桥接效应，导致 30 分钟时的结构化速率显着增加。采用拉拔强度试验和劈裂拉伸强度试验来考察层间结合强度。 S1 SAP 在维持较高的内部相对湿度 (IRH) 方面最显着，从而导致更高的 28 天层间粘合强度，而 S2 SAP 表现出中等的维持较高 IRH 的能力，从而导致 7- d层间结合强度。