| The next five to ten years, a lot of old houses in our country will come into a peak of repairing and strengthening and many new concrete constructs are also faced with a serious issues of the durability. Predictably, quite a long period of time in the future, Chinese construction industry will be completely shift from the new infrastructure mainly to restoration and renovation of infrastructure, so the study about the preparation and application of new type reinforcing material has a very broad prospect. Polymer modified cement based restorative material is mixed with certain proportion of polymer in the cement base material, which could improve the interface transition zone structure of restorative materials and the bonding strength as well as increase the bending capacity. This kind of material is implemented controllable performance through the optimization of design and its performance could meet the requirements of building repair materials.The powders mixture proportions of cement paste composition materials were designed based on the maximum density theoretical model determined by Dinger-Funk equation(hereafter referred to as D-F equation). The correlation coefficient and Euclidean distance were used to characterize the level of similarity between actual mixture proportions and D-F equation about powder particle size distribution. The pore structure of cement paste was tested by mercury intrusion porosimetry(MIP). The relationship between Euclidean distance and fractal dimension of pore volume, as well as the effect of them on compressive strength was analyzed specifically. The results show that Euclidean distance has high correlation with fractal dimension, the correlation is 85.36%. When Euclidean distance decreases from 85.65 to 57.42, fractal dimension increases from 3.17 to 3.21, the compressive strength shows a trend of increase and obtains a maximum value of 123.4 MPa, and the incremental is 27.77%. But when Euclidean distance decreases from 57.42 to 37.61, fractal dimension decreases from 3.21 to 3.03 and the growth of the compressive strength is not obvious.Epoxy resin emulsion is regarded as modifier. The effect of polymer to cement ratios and S/E ratios(the mass ratio of solidification agent and epoxy resin emulsion, the same below) on the mechanical properties and hydration behavior of high density cement mortar was researched. The microstructure of the modified cement mortar was researched by SEM and the pore structure of the modified cement mortar was tested and analyzed through mercury injection porosimetry(MIP). The results show that the polymer accelerates the hydration speed of the modified cement paste in 0-6h, and plays a role of inhibition in 6-15 h and after 15 h. When the S/E ratio was 0.5, the epoxy resin emulsion exists as overlapping fibers after being solidified. The average pore diameter of modified cement mortar increases with the increase of polymer content, while the porosity increases before decreasing. At the same time, the flexural strength and the ratio of compressive to flexural strength decrease and adh esive strength increases. When the content of polymer is 15%, the adhesive strength reaches 2.75 MPa.Basalt fiber is regarded as reinforcing material. The effect of dosages and lengths of basalt fiber on the mechanical properties and pore structure was researched. The pore structure characteristics of fiber reinforced cement mortar was tested by mercury intrusion porosimetry(MIP), and the flexural and compressive strength of cement mortar mixed with different length of basalt fiber were also tested. The results show that the cement mortar mixed respectively with 6+3mm and 12 mm of basalt fiber decrease the porosity by 56.20% and 53.09% dramatically, as well as decrease the compressive to flexural strength ratio by 16.91% and 17.09% significantly. The flexural strength of the cement mixed with 6+3mm of basalt fiber increases with the increase of fiber dosage and the biggest increase is 27.09%. The change of the cement mortar's pore structure and flexural strength mixed with 6mm and 3mm longness basalt fiber was not obvious.Basalt fiber and epoxy resin emulsion were mixed in the cement mortar separately or together. The coupling effect of the basalt fiber and epoxy resin emulsion on the properties of cement mortar w as researched. The results show that the cement mortar has the best liquidity when the fiber content is 1.5% and the ratio of polymer to cement is 7.5%. The addition of basalt fiber and epoxy resin emulsion can effectively reduce the porosity of cement mortar. When the fiber content is 1.5% and the ratio of polymer to cement is 7.5%, the porosity has the minimum value of 6.31%. When the basalt fiber content was controlled at 1.5% and the ratio of polymer to cement is 12.5%, the compressive to flexural strength ratio has the minimum value of 4.14.Ultimately the optimal proportion was determined as below: cement 648 g, silica fume 36 g, superfine cement 216 g, sand 499 g, coarse sand 266 g. The water cement ratio is 0.185 and the dosage of water reducing agent is 3.33 g. The polymer to cement ratio is 10% and solid fat ratio is 0.5. The basalt fiber was double mixed with 6mm and 3mm under the volume ratio of 1:1 and fiber content of 1.5%. The polymer modified cement based restorative material prepared according to the ratio obtained the following performance: the compressive strength is greater than 85 MPa, the flexural strength is greater than 15 MPa, the bonding strength is greater than 2.5 MPa, and the porosity is less than 7%. |
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