Preparation and Primary Evaluation of a New Conservation Material for Earthen Sites in Moisture Circumstance
First of all, the distributing case of earthen site was investigated. And the characters and conservation status quo of earthen site in moisture circumstance were introduced from several aspacts which contained the definition of moisture circumstance, and soil content and structure, the analysis of earthen site disease, summarization of conservation materials for earthen site etc.Secondly, according to earthen site’s property and character, a new conservation material acrylic resin emulsion modified with organic fluorine-silicon was designed and synthesized by semi-continuous core-shell emulsion polymerization reaction. KH-570 and G04 were used as modifying agents, and their content were changed with different emulsion system. According to the determination of total conversion rate of monomers, solid content, gel fraction, emulsion stability, and film properties, the main conclusions are listed as follows:①When the content of KH570 was 55.5% of monomers, the emulsion system’s conversion rate of monomers and solid contents were at a high level, and the gel fraction was low. G04 could approve the conversion rate of monomers(above 95%), however, along with the increase of G04, the gel fraction was also increased. The tests showed that the proper proportion of preparing high-produced acrylic resin emulsion is 5%KH-570 and 3%G04.②With the content of KH-570 as 5.55%, and G04 as 5.16%, the emulsion had best centrifugation stability; with the content of KH-570 as 2.33%, and G04 as 1.10%, the emulsion had best water- , acid-, base- and Ca2+-resistance; all the emulsion system has high dilution stability, nevertheless, the freeze-thaw resistance are low. The emulsion should be stored above 5℃.③XPS showed that F was more easily transferred and enriched on the film surface than Si, which resulted in high hydrophobic property and chemical stability; DSC showed that soft-core and hard-shell structure film was prepared by semi-continuous core-shell emulsion polymerization, and the glass transition temperature could be reduced by KH-570, and increased by G04. FTIR showed that there was no monomers in film, and the system had a better polymerized efficiency, and parts of siloxane hydrolyzed to be Si-OH, other parts were self-crosslinked with Si-O-Si bond. The increase of KH-570 content could reduce water absorption, and acid-, base-resistance, The increase of G04 content not only could reduce water absorption, but also increase the acid-, base-resistance of film.Compacted soil samples, prepared with 20% water content according to the volume weight and void fraction of air-dry soil sampled from southern city wall of Liangzhu site, were consolidated by different fluoro-siloxane modified materials. The research on consolidation efficiency showed that with the content of KH-570 as 5.51%, and G04 as 2.88%, the emulsion had better water-solubility, high penetrability and strong binding force with soil. The soil sample had little change of color, and better gas permeability, water-, acid-, base-, salt-resistance, compression strengthen. The emulsion was suitable for the conservation of earthen sites in moisture circumstance.