盐碱-干湿条件下混凝土强度及耐久性问题研究

Study on Strength and Durability of Concrete under Saline-alkali-dry-wet Conditions

分析了纳米CaCO3掺入量、盐碱浓度等因素对混凝土在盐碱-干湿循环后的强度及耐久性的影响,通过150次的干湿循环,研究了混凝土抗压强度耐蚀系数、质量损失率、相对动弹性模量等耐久性指标随干湿循环的变化规律。试验结果表明,掺入1%的纳米CaCO3可以使28 d混凝土试件获得较高的抗压强度,盐碱-干湿循环条件下2%掺量的纳米CaCO3混凝土试件强度下降最低。纳米CaCO3对混凝土干湿循环中后期的耐久性有明显的提高作用,其最佳掺量为2%,掺量超过2%后则会造成耐久性指标的下降。盐碱浓度对纳米混凝土耐久性的影响随干湿循环次数的增加而增大,且相对动弹模量较质量损失率指标更易受盐碱浓度的影响。

The strength and durability of concrete after saline-alkali-dry-wet cycle were analyzed around the factors such as nano-CaCO3 content and saline-alkali concentration.Through the maximum 150 cycles of dry-wet cycle,the changing rules of durability indexes such as compressive strength,corrosion resistance coefficient,mass loss rate and relative dynamic elastic modulus of concrete with dry-wet cycle were studied.The experimental results show that 1%nano-CaCO3 can increase the compressive strength of 28 d concrete specimens,and 2%nano-CaCO3 can reduce the strength decrease of concrete specimens at the lowest level under saline-alkali-dry-wet cycling conditions.The durability of concrete could be improved by nano-CaCO3 in the middle and late stage of dry-wet cycle,and the optimum content of nano-CaCO3 is 2%.As the content of nano-CaCO3 exceeds 2%,the durability index will decrease.The influence of saline-alkali concentration on the durability of nano-concrete increases with the growth of wet-dry cycles and the relative dynamic modulus of elasticity is more sensitive to the influence of saline-alkali concentration than the mass loss rate index.