This paper focuses on the investigating the effects of various additives on the engineering properties of construction and demolition waste (CDW)-based geopolymer mortars. In this study, low-activity CDW-based precursors, specifically brick waste (BW) and concrete waste (CW), were employed. Additionally, industrial waste-based precursors such as slag (S) and silica fume (SF) were utilized to enhance the overall composition. To facilitate activation, a 5 M solution of NaOH was used. To address the efflorescence issue prevalent in geopolymer mixtures and to eliminate potential cracks that may arise due to the dimensional stability problem of 3D-printed CDW-based geopolymer, various kind of additives including calcite, polypropylene fiber, nano SiO, AlO, and TiO, carbon nano tubes (CNTs), graphene nanoplatelet (GNP), methyl cellulose (MC), NaSiO, calcium oxide (CaO), calcium aluminate cement (CAC), and Ca(OH) were incorporated into the matrix. The research utilized a comprehensive testing methodology, allowing for a detailed exploration of various properties and the performance of the geopolymer mixtures. The results indicated that nano SiO and AlO, NaSiO, BW, and CAC were recognized for their positive impact on improving the mechanical properties of the geopolymer. Notably, the geopolymer exhibited an impressive compressive strength of 29.8 MPa and a flexural strength of 5.4 MPa following a 28-day ambient curing (23 ± 2 °C and 50 ± 5% relative humidity). Furthermore, the inclusion of nano SiO and AlO, GNP, MC, NaSiO, CaO, CAC, and Ca(OH) proved effective in preventing efflorescence, while MC, NaSiO, CaO, CAC, and Ca(OH) successfully mitigated cracks formation. The results also demonstrated that the CDW-based geopolymer mixture is suitable for 3D printing, displaying satisfactory buildability, shape retention, and extrudability. A thorough testing approach highlighted the effectiveness of additives in shaping the properties of CDW-based geopolymer, positioning them as promising for improvement and addressing challenges.

中文翻译：

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可 3D 打印建筑和拆除废物基聚合物：研究添加剂对工程性能的影响

本文重点研究各种添加剂对建筑和拆除废物（CDW）基地聚合物砂浆工程性能的影响。在这项研究中，使用了低活性 CDW 前体，特别是砖废料 (BW) 和混凝土废料 (CW)。此外，还利用工业废物基前体（例如矿渣（S）和硅粉（SF））来增强整体成分。为了促进活化，使用 5 M NaOH 溶液。为了解决地质聚合物混合物中普遍存在的风化问题，并消除由于 3D 打印 CDW 基地质聚合物的尺寸稳定性问题可能出现的潜在裂纹，各种添加剂包括方解石、聚丙烯纤维、纳米 SiO2、Al2O3 和 TiO2，碳纳米管（CNT）、石墨烯纳米片（GNP）、甲基纤维素（MC）、NaSiO、氧化钙（CaO）、铝酸钙水泥（CAC）和Ca（OH）被纳入基质中。该研究采用了全面的测试方法，可以详细探索地质聚合物混合物的各种特性和性能。结果表明，纳米 SiO 和 Al2O、NaSiO、BW 和 CAC 对提高地质聚合物的力学性能具有积极影响。值得注意的是，经过 28 天的环境固化（23 ± 2 °C 和 50 ± 5% 相对湿度）后，地质聚合物表现出令人印象深刻的 29.8 MPa 的压缩强度和 5.4 MPa 的弯曲强度。此外，纳米SiO和Al2O、GNP、MC、NaSiO、CaO、CAC和Ca(OH)的加入被证明可以有效防止风化，而MC、NaSiO、CaO、CAC和Ca(OH)成功地减轻了裂纹的形成。结果还表明，CDW 基地质聚合物混合物适用于 3D 打印，具有令人满意的可建造性、形状保持性和可挤出性。彻底的测试方法强调了添加剂在塑造基于 CDW 的地质聚合物性能方面的有效性，使它们有望得到改进并应对挑战。