Effect of carbonation on chloride diffusion in concrete
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摘要: 混凝土與靜漿快速碳化0,14,28d后浸泡到3.5%NaCl溶液中650d,測試了混凝土不同深度的自由氯離子、總氯離子含量,計算出混凝土的表觀氯離子擴散系數和氯離子結合能力;采用壓汞法測試了不同腐蝕制度下靜漿表層的孔結構,利用DSC分析了靜漿的腐蝕產物.結果表明:混凝土碳化后浸泡到腐蝕溶液中,增加了混凝土中的氯離子含量,提高了混凝土表觀氯離子擴散系數,降低了混凝土對氯離子的結合能力;且隨碳化時間的增加,變化幅度變大.快速碳化粗化了混凝土的孔結構,其大于30nm的毛細孔數量增加了11%,最可幾孔徑增加了17nm;降低了混凝土中Friedel'S生成量,以及混凝土對氯離子的化學結合能力.Abstract: Concrete and paste were immersed in a 3.5% NaCl solution for 650 d after they were quickly carbonated for 0, 14 and 28 d. The free and total chloride contents in different depths of concrete were tested to calculate the chloride apparent diffusion coefficient and the chloride binding capacity. The pore structure and corrosion production of paste attacked by different corrosion regimes were analyzed by mercury intrusion porosimeter (MIP) and differential thermal analysis (DSC), respectively. The results indicate that the chloride content and the chloride apparent diffusion coefficient increase after quick carbonation, however the chloride binding capacity of concrete reduce simultaneously; and the carbonation influence increase with time. Quick carbonation of concrete coarsens its pore structure that the capillary pore (≥ 30 nm) amount of paste increases by 11% and the most probable pore size increases by 17 nm, but it decreases the Friedel'S amount in concrete and reduces the chemical chloride binding capacity of concrete.
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Key words:
- concrete /
- carbonation /
- chloride /
- apparent diffusion coefficient /
- pore structure
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