| Aiming at the problems of low bonding force of existing concrete coatings,low resistance of coatings to chloride ions and insufficient durability of coatings,the concept of combined protection of Controlled Permeable Formwork Liner(CPFL)and organic coatings was put forward.That is to say,the CPFL is pasted on the surface of the original formwork.The CPFL is an organic fiber fabric with the functions of drainage and air permeability,but the permeability of cementitious material particles is not allowed.Under the combined action of concrete lateral pressure and capillary phenomena,water and air bubbles on the surface of concrete are eliminated by formwork cloth,which makes cementitious materials aggregate on the surface of concrete and reduces the water cement ratio on the surface of concrete.At the same time,the accumulated water in the pore of formwork cloth provides the curing water for the early age of concrete,which makes the early hydration complete and the degree of hydration improved,thus improving the quality of surface concrete.By improving the surface quality of concrete,the bonding strength and durability of existing concrete coatings can be improved.The bond strength between formwork and non-formwork concrete at different ages and organic coatings was tested by comparative test.Coating and drawing tests were carried out on 0d,1d,2D and 25 d after removing formwork.Compared with non-formwork concrete and formwork concrete at the same age,the bond strength between formwork concrete and coatings increased by 42% and 26% respectively.16%,43%,which shows that the smoothness and compactness of the concrete surface have a great influence on the bonding strength of the coating.The bonding force of formwork and non-formwork concrete to organic coatings under seawater corrosion condition in early age is 17% higher than that of non-formwork concrete after seawater corrosion for 1 day,which is higher than the minimum difference between them under normal environment;after 7 days of seawater corrosion,the bonding force of formwork concrete and organic coatings is higher than that of non-formwork concrete.The bonding force of non-formwork concrete coatings is still higher than that of non-formwork concrete coatings,but the difference between the two bonding forces tends to decrease.After 28 days of seawater corrosion,the bonding force of non-formwork concrete coatings can still maintain more than 1.5 MPa,and the bonding force of formwork concrete coatings is 19% higher than that of non-formwork concrete coatings.After being corroded by sea water,the bonding force of coatings is affected by the treatment method of concrete surface.When corroded by sea water for 7 days,the bonding force of both non-formwork concrete and formwork concrete after polishing on the crystalline surface is lower than that of untreated original concrete.The bonding force of grinded non-formwork concrete is 6% different from that of original non-formwork concrete in 0d-1d,and 70% in 2d-3d,and 18% to 33% in formwork concrete.After 28 days of seawater corrosion,the bonding force between the surface treated concrete and the coating is greater than that of the untreated original concrete surface,which increases by more than 19%.The regularity of the bonding force of the coating before and after the treatment of the non-template concrete is contrary to that of the template concrete,and the bonding force of the coating after the surface polishing of the concrete is lower.On the untreated raw concrete surface.The results show that the bonding force between concrete and organic coatings can be effectively improved by using formwork cloth.At the same time,the combined protection of formwork cloth and organic coatings has a very obvious effect on hindering chloride on penetration,which can effectively reduce the depth of chloride ion penetration,and the bonding durability between concrete and organic coatings using formwork cloth is significantly improved. |
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