Dima Cristina, Badanoiu Alina, Cirstea Silviu, Nicoara Adrian Ionut, Stoleriu Stefania
Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Str. Ghe. Polizu 1-7, 011061 Bucharest, Romania.
Materials (Basel). 2020 Nov 30;13(23):5454. doi: 10.3390/ma13235454.
This article presents the influence of three additions i.e., hydroxyethyl methyl cellulose (HEMC), sodium bicarbonate and flue gas desulfurization (FGD) gypsum on the porosity of gypsum-based materials. The specific microstructure for a material with good thermal insulation properties i.e., numerous closed pores distributed in the binding matrix, was achieved using HEMC (0.3 wt.%) and sodium bicarbonate (0.5-2 wt.%). The addition of HEMC to the gypsum binder determines, as expected, an increase of the porosity due to its ability to stabilize entrained air. In the case of a sodium bicarbonate addition, the pores are formed in the binding matrix due to the entrapment of the gas (CO) generated by its reaction. Sodium bicarbonate addition delays the setting of gypsum binder therefore in this study FGD gypsum (waste produced in the desulfurization process of combustion gases generated in power plants) was also added to the mixture to mitigate this negative effect. The decrease of geometrical density (up to 13%, in correlation with the additive nature and dosage) correlated with the increase of the porosity, determines, as expected, the decrease of flexural and compressive strengths (33-75%), but improves the thermal properties i.e., decreases the thermal conductivity (9-18%).
本文介绍了三种添加剂，即羟乙基甲基纤维素（HEMC）、碳酸氢钠和烟气脱硫（FGD）石膏对石膏基材料孔隙率的影响。使用HEMC（0.3 wt.%）和碳酸氢钠（0.5 - 2 wt.%）可实现具有良好隔热性能的材料的特定微观结构，即大量封闭孔隙分布在粘结基体中。正如预期的那样，向石膏粘结剂中添加HEMC会因其稳定夹带空气的能力而导致孔隙率增加。在添加碳酸氢钠的情况下，由于其反应产生的气体（CO）被截留，在粘结基体中形成孔隙。添加碳酸氢钠会延迟石膏粘结剂的凝结，因此在本研究中，还将FGD石膏（发电厂燃烧气体脱硫过程中产生的废物）添加到混合物中以减轻这种负面影响。几何密度的降低（与添加剂性质和用量相关，最高可达13%）与孔隙率的增加相关，正如预期的那样，这决定了抗弯强度和抗压强度的降低（33 - 75%），但改善了热性能，即降低了热导率（9 - 18%）。
