防水处理对应变硬化水泥基复合材料孔结构的影响

Influence on pore structure of strain hardening cement-based composites(SHCC) by inside water repellent treatment

水泥基复合材料的抗渗性、耐久性乃至强度等与材料的孔结构密切相关。聚乙烯醇纤维(PVA)增强的水泥基复合材料(SHCC)具有应变硬化和多微裂缝扩展特征,材料具有高抗拉强度、韧性和耗能性,但纤维的添加引入了更多的界面与微裂隙。防水处理技术可以提高此类材料的抗渗性。通过压汞试验研究了硅烷防水剂对PVA-SHCC微观结构的影响,结果表明:最大骨料粒径为1.18 mm时,其总孔隙率约为0.3 mm时的50%,内掺型有机硅类防水剂具有使孔结构细化的作用,其平均孔径和最可几孔径下降为未添加防水剂时的二分之一左右,减少了水泥石中的较大孔隙,改善了水泥浆体孔结构、阻止外界气体、水分、离子向水泥基材料内部的渗透,对于提高SHCC抗渗性非常有效。

Anti-permeability,durability even strength of cement-based composites are closely related with the material pore structure.Polyvinyl alcohol（PVA） fiber reinforced strain hardening cement-based composites（SHCC） are provided with high ductility and multi-micro-crack propagation mode.Due to fibers adding,much more interface and tiny fracture had been drawn into SHCC,although it has some advantages such as high tensile strength,ductility and energy consumption under seismic load or other cyclic force.Water repellent treatment can improve the anti-permeability of SHCC.Investigations have been made through Mercury injection experiment to reveal influence on microstructure of PVA-SHCC by silane water repellence.Results show that,the total porosity will reduce to 50%when the maximum aggregate size changes from 0.3 mm to 1.18 mm and the pore structure of SHCC can be fined by inside water repellent agent.That is,the average pore size and most probable pore size decrease to 1/2,if silane water repellence is added in SHCC.Because the resultant colloids reduce the big hole,pore or fracture and reform the pore structure of the cement paste.The fine pore structure can prevent air,water and ions defuse into interior of cement-based composites,therefore,water repellent treatment is benefit to increase anti-permeability of high ductile SHCC.