Zhou Shuaikang, Zhou Suhua, Zhang Jiuchang, Tan Xin, Chen Deng
College of Civil Engineering, Hunan University, Changsha 410082, China.
Key Laboratory of Building Safety and Energy Efficiency of the Ministry of Education, Hunan University, Changsha 410082, China.
Materials (Basel). 2020 Dec 5;13(23):5550. doi: 10.3390/ma13235550.
The relationship between moisture transportation and efflorescence in sodium hydroxide- or sodium silicate-activated fly ash/slag geopolymers was investigated. The results show that the efflorescence products are sodium carbonate hydrates, mainly composed of natron, heptahydrate, trona and sodium carbonate. The efflorescence induces compressive strength loss, water absorption increases and pore structure degradation in the geopolymer. When the curved surface of a geopolymer cylinder is covered with plastic film, the moisture transportation drives the free alkalis to the top surface to initiate efflorescence. In comparison, the efflorescence occurring on the curved surface of an uncovered geopolymer cylinder results in a more intensive alkalinity loss. For the uncovered geopolymers prepared with sodium hydroxide activator, efflorescence deposits are formed on the lower half of cylinder. A low capillary absorption capacity developed in the pore structure can only drive the moisture to the middle of cylinder, which is confronted with the drying front. More efflorescence products are formed on the upper half of the uncovered geopolymer cylinder prepared with sodium silicate activator. A relatively higher capillary absorption capacity, developed in the more compact pore structure, transports the moisture from the bottom to the top of cylinder, so no drying line is observed in the cylinder.
研究了氢氧化钠或硅酸钠激发的粉煤灰/矿渣地质聚合物中水分传输与泛霜之间的关系。结果表明，泛霜产物为碳酸钠水合物，主要由天然碱、七水合物、天然碱石和碳酸钠组成。泛霜会导致地质聚合物的抗压强度损失、吸水率增加和孔隙结构劣化。当地质聚合物圆柱体的曲面覆盖有塑料薄膜时，水分传输会将游离碱驱赶到顶面引发泛霜。相比之下，未覆盖的地质聚合物圆柱体曲面上发生的泛霜会导致更强烈的碱损失。对于用氢氧化钠活化剂制备的未覆盖地质聚合物，圆柱体下半部分会形成泛霜沉积物。孔隙结构中形成的低毛细吸水能力只能将水分驱赶到圆柱体中部，而中部正对着干燥前沿。用硅酸钠活化剂制备的未覆盖地质聚合物圆柱体上半部分形成了更多的泛霜产物。在更致密的孔隙结构中形成的相对较高的毛细吸水能力将水分从圆柱体底部传输到顶部，因此在圆柱体中未观察到干燥线。
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