Research On Microcapsule Self-healing Technology For Cement Concrete

Because of the initial construction, load, material aging and the influence of external environment factors, the concrete structure will appear inevitably micro cracks and local damage, the repair problem has attracted a lot of attention. The traditional passive repair way, has been unable to meet the current requirements on performance of complex structural parts materials. In order to achieve self- healing of concrete material, the paper firstly synthesized the self- healing microcapsule, and then applied it to the concrete, studied its self-healing performance by the strength and permeability.In this paper, according to the performance requirements of self- healing microcapsule, with a two-component adhesive epoxy resin as core material, formaldehyde and urea synthesis of urea- formaldehyde resin as wall material. The microcapsules synthesized which urea formaldehyde resin coated with epoxy resin by in situ polymerization. The synthesis technology of microcapsule were studied in combination with optical microscope, scanning electron microscope.And the emulsifier types, emulsifier dosage, the ratio of raw materials, the final p H and the stirring rate inf luence on the microcapsule properties were analysised to get to the optimal process: Taking the mass ratio of core material and wall material is 1:1, with 5% compound emulsifier the high-speed shear emulsifying core material, the obtained core emulsion and urea-formaldehyde resin prepolymers are mixed at 450 r / min stirring rate, 70 ℃ for 3 hours at a constant temperature, adjusting the p H value of 3.0, stirring was continued for 2 hours, to obtain microcapsule powder product.The morphology and properties of the microcapsules directly affect the efficiency of repair, so it must be with the aid of scanning electron microscope, laser particle size analyzer to characterize and test the microcapsules. Through experiment it is concluded that: ①Microcapsules substantially spherical,the surface is rough, there is some caking phenomenon;②Microcapsules particle size distribution between 10μm ~ 100μm, and basic normally distributed,the average particle size is 33.51 μm; ③Microcapsule core material content is low, the covering rate is only 57.7%; ④The epoxy resin was successfully coated with urea formaldehyde resin; ⑤Microcapsules have good thermal stability, and its decomposition temperature is 200℃ approximately.Based on microcapsules self- healing concrete, the key is to study the performance of self- healing. By performing tests on the mechanical properties and impermeability resistance with the pre compression injury and not pre compression damage of concrete specimens, studying the effect on the dosage of microcapsule and the degree of damage to the self- healing performance of concrete, draws the following conclusion: Microcapsules for the concrete matrix is a defect and will to a certain exte nt, reduce the strength of the substrate. The microcapsule has no ability to repair the macro cracks formed by bending strength test, but has better performance to repair micro cracks. The strength repair rate and impermeability pressure value of the concrete increase with increment of microcapsule dosage. The microcapsule dosage increase makes the repair agent content increases in the system, there is more repair agent involved in the repair microcracks, so the self- healing effect is more significant, the binary self- healing system of microcapsules and curing agents can give concrete good resistance infiltration performance.