| Rammed earth ancient buildings are important parts of the human history,with extremely high scientific,historical and cultural values.As a type of earth buildings,rammed earth buildings have the largest disadvantage of poor weather ability because it is not baked.At present,in China,earthen buildings in Fujian are the only rammed earth residential buildings that can still give play to use.However,situated in southeast of the Eurasia,Fujian Province belongs to the typical subtropical monsoon climate zone,with frequent rainfalls,and the long-term wind and rain corrosion has seriously reduced the applicability and security of the structure of earthen buildings.Therefore,research and preparation of high-performance surface layer waterproof materials are very important to protection of earthen buildings.In the natural world,lotus leaf with self-cleaning property is a typical super-hydrophobic surface.In combination of experimental methods of bionics,materials science and civil engineering,the surface layer waterproof material suitable for rammed earth walls of earthen buildings with the sol-gel method is adopted in this article.The organic-inorganic hybrid material is a new type of material combined between organic matters and inorganic matters in nanoscale.Based on advantage complementation and function recombination of two or more types of materials,it is available to prepare hybrid materials with excellent performance,which is a hotspot in research at present.In combination of current research results,this article applies hybrid materials with excellent performance to protection of earthen buildings.Firstly,field research on earthen buildings in Fujian in conducted in this article by making brief analysis and generalization to structural features,construction technology and wind and rain corrosion of earthen buildings.Basic physical property test is conducted on local abandoned non-worldheritage earthen buildings,to finish preparation and conservation of rammed earth samples.After that,hybrid materials are selected to acquire suitable hybrid materials,so as to research on influencing factors of organic-inorganic hybrid materials with the sol-gel method,to determine the reaction conditions.The matching ranges of selected materials are determined then based on earlier stage experiment,to acquire the sol needed in the experiment.Finally,the prepared sol is coated on the surface of the test blocks,to analyze and explore the hydrophobic mechanism with ATR-FTIR and scanning electron microscope.The surface chromatic difference analysis is adopted to test the change in colors on surface of the test blocks before and after the application of the coating.The contact angle test,the Casten pipe permeation water absorption test and the Gillon method drip corrosion test are conducted to test the air permeability of the surface of the test blocks before and after the application of the coating layer,and the durability of the coating layer is determined as per the artificial aging test.The article has the following main conclusions:(1)The hybrid materials prepared with PTES and silicon dioxide nano-particles improve the waterproof on surface of the rammed earth of the earthen buildings in an effective way.(2)The water-tolerance effect of the coating layer is mainly determined by contents of PTES and silicon dioxide nano-particles.The coating layer has super-hydrophobicity when the PTES content exceeds 0.008g/ml and the silicon dioxide nano-particle content exceeds 0.01g/ml.The coating not only greatly improves the water tolerance of walls of rammed earth,but also endows walls of rammed earth with certain self-cleaning ability.(3)The change on colors of the coating is mainly determined by contents of silicon dioxide nano-particles.The change on colors will exceed the threshold value of color change perceived by human eyes when the content of silicon dioxide nano-particles exceeds 0.012g/ml.(4)The coating layer gives rise to no influence on air permeability of rammed earth. |
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