在海島型氣候環境下，鋼材銹蝕一直是台灣土木工程普遍存在的問題，尤其是打入有水有土的邊坡地錨。因過去地錨構件之防蝕保護工作，做得並不到位，一旦地下水滲入到地錨鋼絞線後，地下水常會沿著鋼絞線之隙縫，在地錨內部上下流動。一般地錨常以卜特蘭水泥漿灌漿，但水泥漿卻無法充分地滲入鋼絞線封堵隙縫，以致在進行既有地錨現況檢查作業時，發現有些地錨錨頭有地下水滲出情形。
　　因此，本文嘗試以普通卜特蘭水泥、超微粒水泥漿、親水性聚氨酯、疏水性聚氨酯、以及英國Denso防銹油脂等鋼絞線防蝕材料，灌入鋼絞線之隙縫，以切斷其內部之水路。為檢測各防蝕材料之效果，本研究對經不同防蝕材料保護處理之鋼絞線試體，也進行了加速腐蝕試驗。其中，普通卜特蘭水泥之粒徑分布範圍較廣，從較粗到較細之水泥顆粒都有。細顆粒的部分，是有可能將鋼絞線內部孔隙填滿，但其效果較不易確定。超微粒水泥部分，因顆粒細，不需要高灌注壓力，即可自鋼絞線表面滲入隙縫，以堵住鋼絞線內部之隙縫和水路，但因其水泥細度較高，須在灌注時不斷攪拌或添加強塑劑，以防假凝發生。親水性聚氨酯本身具吸水性，長期上，不利地錨之防蝕效果。雖然以銹蝕之重量損失量來說，疏水性PU防蝕效果最佳，但若同時考慮受腐蝕後鋼絲斷裂根數，以及鋼絞線腐蝕情況的話，並非為最適合之防蝕材料。最後，英國Denso防銹油脂本身為稠狀，須加熱至液狀，方可滲入鋼絞線隙縫，但若灌注時遇到棲息水，則會因降溫而快速地轉為稠狀，難以填入鋼絞線之隙縫。
　　綜合上述防蝕材料之性質可知，未加熱之防蝕油脂流動性低，可以停留在錨頭下方；水泥漿流動性高，可以流至遠處。因此，當進行「新設地錨」和「既有地錨」之錨頭和其下方自由段鋼絞線之防蝕保護時，可先行灌注水泥漿至孔口滿漿，若水泥漿面因漏漿而下降時，可再以流動性低之防蝕油脂，填補錨頭下方孔隙，封住孔隙處裸露出來之地錨構件，以達最佳之防蝕保護效果。

Due to the improper corrosion protection and malpractice of ground anchor construction in the past, corrosion was a common problem for ground anchors in Taiwan. Remedial measures were taken to prevent the corrosion of existing anchors from getting worse. If no sign of groundwater leaking was observed, cement grout can be use to fill up the void under the anchorage head and cover the bare tendons. But if groundwater is present, cement grout may not be able to cut off water completely because cement particles may not be able to get in the tiny voids among the wires of the steel strand.
Therefore, this paper attempts to use steel strand corrosion protection materials, such as hydrophilic polyurethane, hydrophobic polyurethane, microfine cement, Portland cement and Denso Void Filler to fill up the tiny voids inside the steel strand and cut off the water flow path to mitigate the corrosion problem of steel strand. The effect of each anti-corrosion material for steel strand was evaluated using the accelerated corrosion tests.
Since the particle size distribution of Portland cement grout is over a wide range. The fine portion of the cement particles is possible to get in the tiny void of the steel strand, but the fill-up effect is not easy to evaluate. Microfine cement grout does not require high pressure to penetrate into the tiny voids from the surface of the steel strand. Because of its fineness of cement particles, it needs to add superplasticizer to prevent false set during gouting. Hydrophilic polyurethane (PU) will react with water in the void of steel strand due to its good penetrability. But the foam produced after reacting with water tends to absorbe water and corrode the steel strand. Hydrophobic polyurethane has the best anti-corrosion effect in terms of weight loss of steel strand. But the number of broken steel wires in the strand after corrosion is the most. Lastly, the Denso Void Filler is a paste-like material under room temperature, so it needs be heated to become liquid-like before it can penetrate into the voids of the steel strand. But it will change back to the paste state quickly when encounters cool groundwater. So, it may have difficulty to fill up the voids of the steel strands.
Based on the properties of the above anti-corrosion materials, it can be found that Denso Void Filler has low fluidity under room temperature and the Portland cement grout has high fluidity. Therefore, when doing anti-corrosion protection for the free length of new ground anchor and existing ground anchor, cement grout can be injected to the anchor first until it overflows from the anchor hole. If the cement grout level drops due to leaking in the anchor hole, the paste-like Denso Void Filler can be injected to fill up the void left behind by the dropping cement grout level. Due to its low fluidity, Void Filler can be used to fill up the void and protect the exposed steel strand in the void and other anchor components under the anchor head. Using the approach, ground anchor with a good corrosion protection can be produced.

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