Study On Anticorrosion And Impermeability Of Repaired Materials With Blending Ordinary Portland Cement And Sulphoaluminate Cement

As repaired material of old concrete,the polymer modified sulphoaluminate cement(SAC)can be used for the construction due to its outstanding durability and waterproof,especially under the harshly environment such as oceaneering.However,the application of SAC was commonly limited by the expensive raw material.In this experiment,to achieve the lowest the cost for repaired material and the outstanding durability,the styrene-butadiene rubber latex(SBR)can be used to modify the blending ordinary Portland cement(OPC)and SAC.The main findings are showed as follows:(1)Blending of OPC and SAC has lots of advantages,such as shorter setting time,lower drying shrinkage and denser microstructure.6% SAC has a positive effect on the compressive strength and drying shrinkage of OPC due to it can produce slightly swell in the hydration process.But when 8%SAC is added,it can decreased the compressive strength of blending cement due to the formation of microcrack,which can be analyzed by the ultrasonic testing.(2)Based on the blending of OPC-SAC,the super fly ash was used to replace the dosage of blending cement.Ternary systems have more compactness structure and excellent physical properties due to the pozzolanic effect and filling effect.The result revealed that 10% fly ash can achieve the most optimal physical property and the best property of waterproof due to it can form more C-S-H gel from reacting with Ca(OH)2 and decrease the porosity.The compressive strength and flexural strength reach to the 59.89 MPa and 10.02 MPa,respectively.The physical property of cement based materials would decrease when more than 15% super fly ash was added.(3)To achieve the lower of energy system,the concentration of SBR latex on surface are higher than that in inner due to SBR latex can reduce the surface tension of solution.SBR latex can improve the fluidity of cement paste due to its hydrophobic group can increase the air-entraining,and a well linear relation between the air content and fluidity of cement paste are observed and correlation coefficient is R2=0.988.When the P/C of 0.5 was added,a boosting of 37.4% and 39.6% for the fluidity of the SBR modified cement paste was achieved.(4)SBR can decrease the porosity of cement based material due to it can form a continued film structure.At 3days,with increasing of P/C,the porosity of SBR modified increased.At 28 days,the P/C of 0.2 and 0.4,the porosity of SBR modified cement reach to the minimum.Air entraining effect increase the porosity of the hardened cement paste and mainly effect on two size range of pore: 0.003~0.01?m and 10~200?m.But at late ages,SBR particles can fill in the pore of hardened cement paste,a reduction of pore size range of 0.03~0.01?m and 10~200?m was resulted and the porosity of modified cement paste is less than that of OPC paste when 2% and 4% SBR latex are added.(5)The compressive strength of SBR modified cement based materials decreased and the flexural strength first decreased and after increased with addition of SBR latex.The ratio of compressive strength to flexural strength,namely it represents the tenacity of mortar,decrease with increasing of SBR content.At the W/C of 0.5,the compressive strength of mortar was trend to a steady value of about 30 MPa.Durability of modified cement based materials has improved when the P/C of 2%-4% SBR was added.However,the excess of SBR content was added,the physical property and durability of mortar decrease due to it can bring lots of bubbles.(6)As repaired material of old concrete,the bonding strength and the micro-structure of interfacial transition zone(ITZ)between the old concrete and repaired materials is very important parameters.Experiments show that the SBR latex can contribute to the bonding strength and decrease the migrating ratio of hydrone result from the hydrophobic functional group has negative for the migrating in concrete.The bonding strength ofsample with the P/C of 15% increase 70%,50% and 58% at 3d,7d and 28 d,respectively,compared with blank sample.In addition,the hydrophobic group decreases the migrating ratio of hydrone.The reduction of migrating ratio of hydrone improves the effective coverage of cement bonding and the orientated growth of Ca(OH)2,so the repair material has an outstanding bonding property.