牡蛎壳颗粒对C40混凝土渗透性的影响和作用机理

Effect and mechanism of oyster shell on permeability of C40 concrete

粉煤灰和矿粉比例为2∶1替代20%的水泥,牡蛎壳替代5%~10%的砂子掺入到C40混凝土中能形成良好级配的混凝土材料,标准养护28 d后其抗压强度提高了约8%,快速氯离子迁移系数(RCM法)下降了48%,P8级渗水平均高度降低了44%。为了研究牡蛎壳颗粒在水泥浆的作用机理,采用牡蛎壳制备了水泥沙浆体,利用扫描电子显微镜(SEM)和X射线衍谢仪(XRD)分析不同水化龄期微观形貌的物相成分,采用电化学工作站分析了电化学阻抗谱(EIS),结果表明:牡蛎壳的表面粗糙、吸水性强,用之代替5%~10%河砂可以降低水胶比,能抑制养护初期(7 d)的钙矾石产生,从而提高混凝土的抗压强度,与此同时,牡蛎壳颗粒能大幅提高中频极化电阻和降低低频扩散系数,因此能提高混凝土抗渗透性能。

The fly ash and mineral powder in a ratio of 2∶1 instead of 20%cement and crushed oyster shell instead of 5%~10%sand could be mixed into C40 concrete to form good graded concrete material.After 28 d of standard curing,its compressive strength increased by about 8%,the rapid chloride migration(RCM)coefficient decreased by 48%and the average seepage height of P8 grade is reduced by 44%.In order to study the mechanism of crushed oyster shell on the permeability of C40 concrete,the cement slurry were prepared by mixing crushed oyster shell single separately,the micro-morphology changes of the cement slurry at different hydration ages were analyzed by scanning electron microscopy(SEM),the phase composition of different hydration ages were analyzed by X-ray diffractometer(XRD),and the electrochemical impedance spectroscopy(EIS)was analyzed by electrochemical workstation.The results showed that crushed oyster shell can reduce the water-binder ratio of concrete by replacing river sand and inhibit the production of ettringite at the initial stage of curing(7 d)because of the its rough surface and strong water absorption,thus adding 5%~10%crushed oyster shell can increase strength improve the compressive strength of concrete.Oyster shell can improve the corrosion resistance of concrete greatly because it increases polarization resistance in the medium frequency of and reduce the low frequency diffusion coefficient in EIS.