Xie Yuekai, Wang Hongxu, Guo Yingying, Wang Chenman, Cui Hanwen, Xue Jianfeng
School of Engineering and Technology, The University of New South Wales, Canberra, ACT 2612, Australia.
School of Engineering and Technology, The University of New South Wales, Canberra, ACT 2612, Australia.
Sci Total Environ. 2024 Feb 20;912:168773. doi: 10.1016/j.scitotenv.2023.168773. Epub 2023 Nov 24.
The applications of magnesium oxychloride cement (MOC) have been extensively studied recently due to its eco-friendly and high-strength nature. However, one of the significant limitations of MOC is its poor water resistance. To address this limitation, this study explored the prospect of incorporating biochar particles (up to 25 % of the dry mass of MgO) to form lightweight MOC with improved water resistance. The compressive (f) and flexural (f) strengths were investigated after 28-day curing and under 56-day water attack. The f of MOC after immersion was determined under both wet (directly after immersion) and dry (air-dried to constant weights) conditions. The results indicated that the inclusion of 5 % and 10 % biochar increased the 28-day f, while the addition of biochar decreased f regardless of its dosage. Microscopic examination uncovered that the increase in strength resulted from the promoted production of phase 5 (5 Mg(OH)·MgCl·8HO) and the reduction in unreacted MgO. The inclusion of 5 % and 10 % biochar increased the compressive and flexural strength retention ratios after 56-day immersion. The f with 5 % biochar inclusion after immersion was higher compared to that of pure MOC. Moreover, the inclusion of biochar had minimal effects on the thermal degradation of MOC. The above results suggest that biochar can be a potential additive to enhance the mechanical behaviour and water resistance of MOC. As f of immersed MOC increased during air-drying, a new equation was developed to describe variations in f of MOC subject to different degrees of saturation during drying.
近年来，由于氯氧镁水泥（MOC）具有环保和高强度的特性，其应用得到了广泛研究。然而，MOC的一个显著局限性是其耐水性较差。为了解决这一局限性，本研究探讨了掺入生物炭颗粒（高达MgO干质量的25%）以形成具有改善耐水性的轻质MOC的前景。在28天养护和56天水侵蚀后，对其抗压强度（f）和抗折强度（f）进行了研究。在湿（浸泡后立即）和干（风干至恒重）两种条件下测定了浸泡后MOC的f。结果表明，掺入5%和10%生物炭可提高28天的f，而无论生物炭用量如何，其添加都会降低f。微观检查发现，强度增加是由于促进了5相（5Mg(OH)·MgCl·8H₂O）生成以及未反应MgO减少。掺入5%和10%生物炭可提高56天浸泡后的抗压强度和抗折强度保留率。掺入5%生物炭后浸泡的f高于纯MOC浸泡后的f。此外，生物炭掺入对MOC热降解影响最小。上述结果表明，生物炭可作为一种潜在添加剂来增强MOC的力学性能和耐水性。由于风干过程中浸泡MOC的f增加，因此开发了一个新方程来描述干燥过程中不同饱和度下MOC 的f变化。
