Qiwei Zhan,Wanying Dong,Changhao Fu,Anhui Wang,Haihe Yi,Zhihong Pan
To achieve the goal of self-healing of marine concrete cracks and fixation of harmful ions invading the cracks, researches on the synergy of microbial mineralization and inorganic mineral hydration were carried out. The fixation effects of Cl − , SO 4 2− and OH − in simulated solution with different inorganic mineral dosages were tested by experiments. Further, the growth performances of microorganisms in the modified simulated solution were also tested. Finally, the self-healing effect of cracks in cement-based materials was experimentally verified. The results showed that the Cl − and SO 4 2− in the simulated solution can be effectively fixed by the double metal hydroxide , and combined with a part of H 2 O to form hydration products that accumulated in the deep region of the crack. A large amount of OH − were also consumed for the formation of double metal hydroxides, which greatly lowered the pH of the simulated solution. Thus, the chemical environment of the simulated solution became suitable for the growth of microorganisms, and the number of microorganisms in the solution increased significantly. Eventually, the hydration product and the mineralization product area were connected to form a superimposed repair zone, thereby expanding the repair scope. The test results could provide reference for concrete crack self-healing and anti-corrosion of buildings applied on marine environment.
Wenmei Tao,Wenyan Duan,Chunbo Liu,Dongdong Zhu,Xiaoxi Si,Ruizhi Zhu,Patryk Oleszczuk,Bo Pan
The presence of persistent free radicals (PFR) in biochars may greatly broaden the application of biochars in pollution control , but may also cause negative impacts to the environment. Understanding the structural basis and the formation mechanisms of PFR is essential for a targeted biochar production and application. This study used rice straw (RS), a ubiquitous agricultural waste , to investigate the generation processes of PFR in relation to RS pyrolysis kinetics. Based on a detailed thermogravimetric (TG) and derivative thermogravimetric (DTG) analysis, the activation energy was calculated by Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods. This work combined pyrolysis kinetics analysis and solid particle characterization. Our results showed that lignin started to pyrolyze at a lower temperature than cellulose and hemicellulose. Lignin was the main factor for PFR generation. Chemical bond breaking contributed only slightly to PFR formation. The reconfiguration of the carbonaceous structures may be a more important contributor to PFR formation, while the cross-linking between different compositions and the interactions between the chemical compositions and inorganic minerals may play a significant role for PFR generation and stabilization in RS. This study provides useful theoretical basis to understand the thermal pyrolysis process of RS and the manipulation of biochar properties.
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