矿物掺合料对混凝土耐久性的影响

Influence of Fly Ash on Concrete Durability

采用海水热雨循环90次、海水浸泡90d两种试验条件对比研究了4种混凝土的强度、扩散系数、电通量和钢筋腐蚀电位等性能变化。结果表明,经热雨循环90次试样抗压强度较海水浸泡90d的高,掺加粉煤灰降低混凝土试样的早期强度,提高中后期强度;经热雨循环90次试样扩散系数较标样28d试样高,但电通量降低,海水浸泡90d试样扩散系数和电通量均较28d试样低,C30级试验扩散系数和扩散系数较C50级高,掺加粉煤灰提高混凝土试样28d的扩散系数和电通量,但降低海水浸泡90d和热雨循环90次的扩散系数和电通量;经热雨循环90次试样内钢筋腐蚀电位较标样28d试样低,海水浸泡90d试样内钢筋腐蚀电位较28d试样低,但高于热雨循环90次试样,C30级混凝土试样钢筋腐蚀电位下降幅度较大,个别试样内钢筋发生点蚀,掺加粉煤灰提高试样内钢筋腐蚀电位,对耐久性有利。

Using heat and seawater shower cycles 90 times and seawater immersion 90 days,the strength,diffusion coefficient,flux and corrosion potential of four concretes were comparatively studied.The results showed that compressive strengths of samples by 90 times heat and seawater shower cycles were higher than samples by 90 days seawater immersion;the adding of fly ash could reduce the strengths of concretes of early age,but decrease the strengths of concretes of later age.Diffusion coefficients of samples by 90 times heat and seawater shower cycles were higher than samples cured in standard condition for 28 days,but flexes were lower;diffusion coefficients and flexes of samples by 90 days seawater immersion were both lower than samples cured in standard condition for 28 days.The adding of fly ash could increase the diffusion coefficients of concretes of early age,but increase the strengths of concretes of later age;the corrosion potential of rebar of samples by 90 times heat and seawater shower cycles were lower than samples cured in standard condition for 28 days.The corrosion potential of rebar of samples by 90 days seawater immersion were also lower than samples cured in standard condition for 28 days,but higher than samples by 90 times heat and seawater shower cycles;the corrosion potential of rebar of concretes of C30 grade by 90 times heat and seawater shower cycles were much lower than C50 grade,and pitting could be found on the rebar of that.Adding of fly ash into concrete could increase the corrosion potential.And it is beneficial to the durability of concrete.