The Research On Repairing Of Grey Brick And PHBV For Preservation Of Grey Brick

As one of the common building materials in the existing historical building ruins in China,grey bricks play the role of load-bearing and enclosure.And some of the grey bricks also have the function of architectural decoration aesthetics.However,due to factors such as long-term wind and sun exposure,soluble salt erosion,and man-made damage,grey bricks are in a very serious disease situation,including cracks,pan-alkali water stains,and biological diseases.The research on the protection of grey bricks is urgent.In this paper,the grey bricks of the Ming Dynasty Great Wall of Beijing are taken as the protection objects.Meanwhile,the traditional inorganic protective materials and the modified biodegradable material PHBV are used to protect the grey bricks respectively,and the protective effect and durability are studied.(1)The protection effect of traditional inorganic materials on grey bricks.Calcium hydroxide and natural hydraulic lime are used to repair the scratched grey bricks.And the repair effect of traditional protective materials is characterized by comparing the performance parameters of the repaired samples before and after aging,such as morphology,color difference and hardness.The results show that the bonding strength between the natural hydraulic lime as the repairing material and the brick matrix is weak.For the grey bricks repaired with slaked lime;.The bonding strength between the repairing material and the matrix is high,which meets the requirements of the cultural relics as old,but the repairing material and the grey brick substrate is prone to produce powder and flaking on the surface after long-term high humidity erosion,and the blue brick needs surface protection.(2)The protective effect of nano-TiO2/PHBV and nano-CeO2/PHBV emulsion on grey brick.Modified nano-TiO2 and nano-CeO2 to compound with PHBV emulsion respectively.Appling the composite emulsion to the surface of grey brick and evaluating the modification effect by infrared spectroscopy and XRD test,the color difference change and capillary water absorption of the coated sample Coefficient,surface contact angle and other protective effects.After coating,the hydrophobicity of the surface of the blue brick is increased,the water permeability is reduced,the water vapor permeability is good,and the sample is resistant to ultraviolet aging.Among them,the contact angle of the nano CeO2/PHBV coated blue brick is as high as 127.5 °.And the capillary water absorption coefficient Between 0.0007-0.0037 g/(cm2·s0.5),which is far lower than 0.0131 g/(cm2·s0.5)when unapplied.The optimal amount of nano CeO2 is 1%.(3)The protective effect of PHBV microspheres on grey bricks.Using solvent evaporation method to prepare PHBV microspheres.Exploring the influence of various factors(temperature,PVA concentration of external water phase)on the microsphere appearance and particle size.Optimizing the microsphere particle size preparation parameters,and its composition,particle size and micromorphology after the characterization,the preliminary research on the protection of the surface of the blue brick after compounding with the silane coupling agent.The optimal reaction temperature is 10? and PVA content is 4%at preparing PHBV microspheres.After coating PHBV microspheres with different particle sizes on the surface of grey bricks,they have different effects on the surface hydrophobicity of the sample.The hydrophobicity of the surface is relatively better.