| Degradation of concrete structure caused by erosion media has become one of the most serious durability-related problem, affecting the service life of reinforced concrete especially under the coastal marine environment. Polymer cement waterproof coating(JS) is noval founded.waterproof material, presenting excellent waterproofing performance, Polymer cement waterproof coating presents both good durability of cement-based materials and high strength and toughness of polymers, besides, it also has good binding property and is proved nonpoisonous and tasteless. However, there still many durability-related challenges for this coating, such as inadequate water resistance, poor corrosion and weather resistance, leading to a reduced service life. Considering the problems above, this thesis aims at developing a new type of polymer cement water proofing coating material applied in coastal atmospheric environment with improved properties. The mixture proportion was optimized by investigating the effects of material composition and polymer/cement ratio on the performance of JS waterproof coating. Meanwhile, JS waterproof coating was modified with silica ultrafine powders, to enhance the corrosion, weather and water resistance. The modified waterproof coating can be applied for the surface protection of buldings under coastal atmospheric environment and the investigations in thesis has important practical values. The research content of this thesis are summarized as follows:(1)The effects of the additives, filler and polymer-cement ratio(P/C) on the performance of JS waterproofing coating were investigated. First, the orthogonal test indicate that the optimum dosages of defoaming agent, coalescing agent, flatting agent and dispersant were 0.4%, 3%, 1.5% and 0.4% respectively. The coating porosity was the lowest only 0.34%, when the content of defoaming agent content was 0.4%. The film-forming agent reduced the porosity and tensile strength and increased the water absorption and breaking elongation of JS waterproofing coating..(2) Among the commonly used fillers, light calcium carbonate improved the water absorption, fly ash increased the mechanical properties and talcum powders improved the breaking elongation of JS waterproofing coating. When a high polymer/cement ratio was used, the hydration degree of cement in the coating was increased; the JS waterproofing coating presented good rheological property(lower viscosity) and reduced coating defects, but increased water absorption. After the coating was immersed in water, Ca(OH)2 content decreased and Ca(CH3COOH)2 content increased, leading to a reduced bond strength and increased tensile strength.(3) Silica ultrafine powders was modified by KH-550 to improve its dispersivity. After the modification, new Si-O-Si covalent bond was formed on the surface of modified silica ultrafine powders and the amount of adsorbed water was reduced, leading to a smaller aggregate number and reduced particle size. The influence of modified silica ultrafine powder on the performance of ethylene/vinyl acetate(EVA) emulsion was investigated. When 1 % modified silica ultrafine powders was admixed, the formed film of EVA emulsion was denser, and a lower water absorption and improved mechanical property was achieved.(4) The polymer cement waterproof coating modified by silica ultrafine powder was prepared. By the modification of silica ultrafine powders, the cement hydration of JS waterproof coating was accelerated, leading to a higher amount of Ca(OH)2 and C-S-H, reduced drying time of coating, increased contact angle, shear stress and viscosity and reduced coating fluidity. When 1 % modified silica ultrafine powders were used, the water resistance, acid resistance, alkaline resistance, weather resistance and aging resistance, adhesion proeperty and mechanical property of coating were significantly enhanced. By using JS waterproof coating with 1 % modified silica ultrafine powders, concrete specimen presented a lower water absorption ability and higher corrosion resistance to seawaster.(5) The protection effect of the JS waterproof coating modified by silica ultrafine powders on concrete were investigated. Compared with other coatings, in the aspect of carbonation resistance, CaCO3 content was the lowest in the surface layer(0-5 mm) for the specimen with JS waterproof coating(specimen PC); further, up to 35 days, the carbonation depth was only 3.1 mm for specimen PC, compared to the carbonation depth of 3.4 mm for the specimen with epoxy resin coating(specimen EC). In the aspect of resistance to sulfate attack, Ca(OH) 2 content on the surface layer of 0 ~ 2 mm was the highest for specimen PC(5.70%), and the slowest mass loss rate and reduction coefficient of compressive strength was also the lowest for specimen PC. In the aspect of water absorption and corrosion resistance to seawater: the capillary suction coefficient and Cl-1 penetration depth for specimen PCwere slightly less than specimen EC, but higher than specimens with polymer emulsion coating and organic silicon coating.To be summarized, the JS waterproof coating modified with silica ultrafine powders(EVA emulsion: 150.00 g; coalescing agent: 9.04 g; modified SiO2 ultrafine powders: 1.50 g; dispersant: 2.00 g; fillers: 115.00 g) presented excellent weather resistance, corrosion resistance and durability and can efficiently inhibit the erosion of water, chlorides, CO2 and sulfate on concrete. The JS waterproof coating modified with silica ultrafine powders prepared in this study can be applied for the effective surface protection of concrete structures under the coastal atmospheric environment, which will play an important role in the implementation of ocean development strategy in our country. |
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