Study On Protective Material For Concrete Structure Based On Fiber Ploymer Mortar

With the continuous excavation of concrete performance,various high performance concretes have been extensively developed and applied.At the same time,the environment is also changing.The harsh environment will cause serious damage to concrete.Especially in the environment with high humidity,high temperature,high salt and high acid mist condensation,the problems of protective layer shedding and steel corrosion will happen on many concrete structures.If the building structure happens damage and damaged only on the protective layer,it does not need to be rebuilt,only a small amount of repair mortar should be used for protective repair,which will be more effective and more conducive to the wide application of concrete.In this paper,in order to meet the requirements of the"four good protective repair mortar"with good workability,good toughness,good adhesion and good durability,polymer and anti-cracking fiber is firstly added to the sulphoaluminate cement（SAC）-based mortar for modification and toughness enhancement;then early strength agent is further added to ordinary Portland cement（PO）-based mortar to improve early strength along with quantitatively adding polymer and anti-cracking fiber;finally the durability of two cement series repair mortar is systematically investigated with the preferred ratio given.The main contents and conclusions are as follows:1.The three-factor and three-level orthogonal test method is used for preparing SAC mortar,and the workability,mechanical properties,impact toughness and bond strength are used as the control indexes to study three factors of the cement-sand ratio（C/S）,the polymer-cement ratio（P/C）,and anti-cracking fiber content(ω_XW)on the SAC mortar performances.Results show that,1)with the C/S increase,the fluidity,impact toughness,flexural strength（f_t）and compressive strength（f_c）are gradually increased,respectively;the bond strength（f_b）is little affected,showing first increase and then decrease trend.2)As the amount of polymer increases,the f_t,f_b and impact toughness are all improved,while the fluidity and f_c are gradually reduced.3)With theω_XWW increase,the impact strength gradually increases,and the fluidity,f_t and f_c show increase first and then decrease trend.2.PO mortar is firstly tested by single factor test method to investigate the early strength agent effect（calcium formate,anhydrous sodium sulfate,calcium acetate and triethanolamine）on the early strength of PO mortar（f_c,f_t for 1d,3d and 7d,and f_b for14d）or along with adding 8%polymer and 1.5kg/m³ anti-cracking fiber.Then the preferred ratio of SAC mortar is applied to the PO series to develop a preferred ratio of the PO series.The results show that,1)The optimum dosage of four early strength agents of calcium formate,anhydrous sodium sulfate,calcium acetate and triethanolamine is 1.5%,1.0%,0.7%and 0.05%,respectively;2)The best effect is in order of triethanolamine>anhydrous sodium sulfate>calcium formate>calcium acetate for f_t.The increase in f_c is triethanolamine>anhydrous sodium sulfate>calcium formate>calcium acetate;3)The effect of four early strength agents on the f_b is almost the same as those of the blank group.Combined with the dosage of early strength agent and cost-effective,0.05%triethanolamine can be chosen as early strength agent for the final application.3.Durability tests show that,the shrinkage property,anti-permeability,anti-freezing performance,and anti-carbonization performance of two cement series mortars（SAC and PO）,either single-doped polymer,single-doped anti-cracking fiber,or compounded with polymer and crack-resistant fiber,have a certain improvement;the SAC series mortar combined with polymer and anti-cracking fiber has a drop on shrinkage rate of 16.38×10^-5,a decrease of chloride ion diffusion coefficient of 19.2%,and the carbonization depth is decreased by 15.4%,while compared with the blank group.The PO series mortar combined with polymer and crack resistant fiber has a decrease of 16.0×10^-55 on 90d shrinkage rate,decrease of 15.8%on the chloride ion diffusion coefficient,and the carbonization depth is reduced by 17.3%compared with the blank group.In addition,through the sulfuric acid immersion test,it is found that the f_c with protective coating is significantly higher than that without the protective coating,which embodies the protective effect of the anticorrosive coating.4.The cost-optimized reference ratio of fiber polymer mortar used for concrete structure protection is:SAC series W/C=0.31,C/S=1:1.5,P/C=8%,ω_XW=1.5kg/m³,the amount of water reducing agent is 0.3%of the cementitious material,and the PO series plus 0.05%triethanolamine early strength agent.