鋼纖維混凝土預裂梁於長期循環鹽霧劣化氯離子分佈與鋼筋腐蝕研究

Abstract

近年來氯離子耐久性逐漸受到重視，台灣於氯離子耐久性研究也漸趨成熟：全台飛來鹽統計、混凝土氯離子擴散行為、鋼筋銹蝕之耐震性能折減等研究之間，逐漸可開始成形為一套系統。然而目前針對混凝土內部鋼筋銹蝕程度尚無法以非破壞形式對其進行準確評估，因此若能在實際鋼筋腐蝕與非破壞性監測結果建立起關聯，將可使氯離子耐久性研究更為完善。 本研究接續本研究團隊過去設計鹽霧加速劣化約2100天之預裂梁進行實驗，藉此探討實驗設計之3項變因(混凝土開裂、是否配置箍筋、不同鋼纖維添加量)對3項實驗結果(混凝土氯離子耐久性、腐蝕電流量測、鋼筋重量損失率)之影響，並將實驗結果用於驗證鋼筋腐蝕預測模型之適用性。希望可透過上述實驗獲得本研究試驗變因對腐蝕電流應用於評估鋼筋腐蝕程度影響之定性結論。 依不同實驗變因之研究結論顯示，混凝土開裂將導致鋼筋銹蝕加劇；箍筋配置不會導致腐蝕電流評估鋼筋真實腐蝕狀態失準；鋼纖維添加於高強度混凝土則會導致腐蝕電流低估鋼筋真實腐蝕狀態。 將實驗結果透過腐蝕預測模型進行驗證後，得知NS+2試體可透過腐蝕電流量測準確評估內部鋼筋腐蝕狀態；HSSF0+2試體驗證結果雖然有所差異，但相去不遠，進一步完善腐蝕預測模型應可獲得準確結果；而HSSF075與HSSF150則受到鋼纖維影響，驗證結果差異甚大。綜上所述，本研究未添加鋼纖維之試體，可透過腐蝕預測模型獲得一定程度精準之評估結果，然而含有鋼纖維之試體，該模型目前尚不適用。

In recent years, the durability of concrete structures against chloride has garnered increasing attention, with Taiwan's research in this field gradually maturing. Studies including nationwide statistical data on airborne salt deposition, chloride diffusion in concrete, and the seismic performance reduction due to reinforcement corrosion are beginning to form a comprehensive system. However, current methods for non-destructive evaluation of internal reinforcement corrosion in concrete remain insufficiently accurate. Establishing correlations between actual reinforcement corrosion and non-destructive monitoring results could significantly enhance the study of chloride durability. This study continues experiments on pre-cracked beams, exposed to salt spray for approximately 2100 days, previously designed by our research team. The aim is to investigate the effects of three experimental variables (concrete cracking, use of stirrups, varying steel fiber content) on three experimental outcomes (chloride durability of concrete, corrosion current measurement, steel weight loss rate). These results will be used to validate the applicability of a corrosion prediction model for reinforcing steel. Through these experiments, the study seeks to draw qualitative conclusions on how the experimental variables influence the assessment of steel corrosion severity using corrosion current. According to the findings from different experimental variables, concrete cracking exacerbates steel reinforcement corrosion. The presence of stirrups does not lead to accurate assessment of corrosion current in evaluating actual steel corrosion status. The addition of steel fibers to high-strength concrete results in underestimation of corrosion current in assessing actual steel corrosion status. Validation of the experimental results through corrosion prediction models reveals that the NS+2 specimen allows accurate evaluation of internal steel reinforcement corrosion status through corrosion current measurements. Although there are some discrepancies in the verification results of the HSSF0+2 specimen, they are relatively minor, suggesting that further refinement of corrosion prediction models could yield accurate results. However, significant differences are observed in the verification results of the HSSF075 and HSSF150 specimens due to the influence of steel fibers. In summary, the specimen without steel fibers provides reasonably accurate evaluation results through the corrosion prediction model. Yet, the model currently proves inadequate for specimens containing steel fibers.