【摘要】 将C30和C50系列引气混凝土在质量分数5%Na2SO4或5%Na2SO4+3.5%NaCl溶液中自然浸泡或快速冻融循环,测试盐冻过程中混凝土表面和内部的超声声时、混凝土中水溶及酸溶SO2-4质量分数、孔结构演变和热谱.结果表明:超声声时能较好反映混凝土在盐冻过程中的损伤演化,其表面和内部超声声时均先轻微上升,然后保持稳定,当混凝土损伤严重时迅速上升.冻融过程中的低温环境可降低混凝土中SO2-4扩散速度和反应SO2-4量,但冻融损伤程度的增加将导致混凝土中SO2-4扩散速度增加.混凝土在复合盐溶液中冻融循环时,其SO2-4反应能力是Na2SO4溶液中盐冻混凝土的2倍,生成的钙矾石、硅灰石膏和石膏腐蚀产物更多,毛细孔增加2.2倍,最可几孔径提高了8nm,混凝土表面剥落更为严重.更多还原

【Abstract】 The deterioration,sulfate ion distribution,pore structure and corrosion product of concretes under attack of sulfate frost were systematically investigated.The compressive strength grades of air entrained concrete were C30 and C50.The corrosion regimes were employed:freeze-thaw cycles in 5%(by mass)Na2SO4or in 5%(by mass)Na2SO4+3.5%(by mass)NaCl mixed solution,and naturally immersion into above-mentioned solution with same time of freeze-thaw cycles.The damage degree of concrete was tested by ultrasonic,its pore structure was tested by MIP,and the corrosion product of concrete subjected to sulfate frost was analyzed by TG-DSC.The experimental results show that the ultrasonic time passes through the interior and surface of concrete under attack of sulfate frost increases slightly at first,then keeps steady,finally decreases to failure due to mass loss and deterioration of concrete.The low temperature in sulfate frost environment reduces sulfate ion permeability velocity and the sulfate ion reacting ability with concrete.But increasing damage degree in concrete resulted by sulfate frost will accelerate sulfate ion penetration into concrete.Compared with concrete subjected to 5%Na2SO4frost,the sulfate ion reacting ability with concrete increases to double and the capillary pore enlarges by 2.2times for concretes subjected to mixed solution frost.Due to the existence of chloride ion in mixed solution,the amount of corrosion product of concrete under attack of mixed salt frost,including ettringite,gypsum and thaumasite,is more than that of concrete subjected to sodium sulfate frost.Additionally,the degree of surface scale of concrete subjected to mixed salt frost is more serious compared to concrete in sulfate frost.更多还原