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Property Evaluation of Cement-based Composites Containing Fibers and Supplementary Cementitious Materials
|Contributors: ||NTOU:Department of Harbor and River Engineering|
polyolefin fiber;silica fume;rock wool;direct tensile strength;rapid migration test;toughness;permeability
|Issue Date: ||2011-10-20T08:11:11Z
|Abstract: ||本研究係探討添加纖維與輔助膠結料對水泥質複合材料力學性、滲透性與微觀結構的影響，並探討廢棄岩棉應用於水泥質複合材料的方式與特性。試驗結果顯示：(1)使用鋼纖維能有效改善劈裂強度、直接拉力強度、韌性與抗衝擊性，添加矽灰能改善抗壓強度與抗磨耗性；(2)鋼纖維能提高複合材料極化阻抗，而矽灰能降低滲透性；鋼纖維降低吸水率、擴散係數與滲透深度的效能不及矽灰；(3)使用聚烯烴纖維能增加抗壓強度、降低吸水率、擴散係數與滲透深度，並能提升抗拉強度、韌性與抗衝擊性，而聚烯烴纖維長度對試驗結果無顯著影響；(4)矽灰與纖維混合使用會顯著提高強度、降低滲透性；由電子顯微鏡觀測與壓汞試驗證實使用矽灰能形成較多且緻密的CSH膠體，減少孔隙孔徑並助於增加強度與提高漿體與纖維間的黏結力；(5)使用岩棉能有效增加力學性質並降低滲透性，當岩棉的粒徑尺寸低於75μm時，卜作嵐活性指數(>75%)顯示岩棉能提供額外之膠結能力；(6)添加10 vol.%岩棉試體劈裂強度約與添加2 vol.%鋼纖維試體強度相同。直接拉力強度較劈裂抗拉強度低，此因劈裂試驗試體受二維拉壓圍束效應所致，而直接拉力試驗較能均勻傳遞拉應力。吸水率、氯離子擴散係數、氯離子滲透深度與極化阻抗可用於評估水泥質複合材料滲透性，然快速氯離子穿透試驗不適於評估含鋼纖維複合材料，因鋼纖維會影響導電性，導致試驗結果有偏差。|
This study is aimed to evaluate the mechanical properties, permeability and microstructure of cement-based composites containing various fibers and supplementary cementitious materials. The technique and effectiveness of utilizing rock wool was investigated and compared.
Test results demonstrate that (1) steel fiber composites provide better performance in splitting tensile strength, direct tensile strength, toughness and impact resistance while silica fume composites significantly increase the compressive strength and abrasion resistance; (2) silica fume composites can significantly improve the permeability. On the other hand, steel fiber composites increase the polarization impedance and also reduce the diffusion coefficient and penetration depth, but not as effective as silica fume composites; (3) polyolefin fiber composites show a significant improvement in tensile strength, toughness and impact resistance, but little improvement in compressive strength, absorption, diffusion coefficient and penetration depth. However, the polyolefin fiber length has less influence on the mechanical properties and permeability; (4) it is confirmed that the combination of fiber and silica fume has positive effect on the mechanical properties and permeability. This is because silica fume in the fiber composites can narrow down the size of large capillary pores, densify the pore structure and enhance the bonding strength between fiber and paste; (5) rock wool composites increase mechanical properties and also decrease permeability. With sizes less than 75μm, the test result of pozzolanic activity index (>75%) indicates that rock wool composites can provide extra cementitious capability; (6) the results of splitting tensile strength of 10 vol.% rock wool composites is close to that of 2 vol.% steel fiber composites.
According to the result of tensile strength test, the splitting tensile strength is higher than the direct tensile strength due to the effect of biaxial stress. In direct tensile strength test, the loading is transmitted through the embedded rebar and no stress concentration is produced. Moreover, the absorption, chloride diffusion coefficient, penetration depth and polarization impedance are suitable for evaluating the permeability of cement-based composites. The 6-hour total charge-passed is not suitable as a criterion to evaluate the permeability of steel fiber composites. This is because the current density increases as the conductivity decrease during the test. An incremental change in current density will increase the mobility of all ions, which in turn will raise the total current flow.
|Appears in Collections:||[河海工程學系] 期刊論文|
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