机制砂与特细砂抗氯盐侵蚀混凝土的制备及性能研究

Preparation and Properties of Chloride Resistant Concrete with Manufactured Sand and Extra Fine Sand

利用机制砂、特细砂等制备抗氯盐侵蚀混凝土对降低生产成本、提升桥梁服役寿命具有重要意义。本研究通过优化骨料设计与水泥浆体组成提升混凝土的抗氯离子侵蚀性能,研究了骨料级配、特细砂用量、砂率、水胶比、胶凝材料种类对混凝土性能的影响。结果表明:8~16 mm碎石质量分数由50%增加至80%时,氯离子扩散系数由4.0×10^(-12)m^(2)/s降低至2.9×10^(-12)m^(2)/s;特细砂替代50%(质量分数)机制砂时,氯离子扩散系数为3.6×10^(-12)m^(2)/s,仍可以满足设计要求;砂率增大,氯离子扩散系数先减小后增大。水胶比在0.36~0.38时,氯离子扩散系数低于3.5×10^(-12)m^(2)/s;矿渣组分水化改善了混凝土的孔结构,并形成了更多的AFm、C-S-H产物,提升了混凝土对氯离子的固化能力,矿渣水泥混凝土氯离子扩散系数较普通硅酸盐水泥混凝土降低了40%。

Using manufactured sand,extra fine sand and other materials to prepare chloride resistance concrete is of great significance to reduce production costs and improve the service life of bridges in coastal areas.In this study,the chloride resistance of concrete was improved by optimizing aggregate design and cement paste composition.The effects of aggregate gradation,extra fine sand content,sand ratio,water-binder ratio and cementitious material type on concrete performance were studied.The results show that the chloride diffusion coefficient decreases from 4.0×10^(-12)m^(2)/s to 2.9×10^(-12)m^(2)/s when the mass fraction of 8~16 mm gravel increases from 50%to 80%.When 50%(mass fraction)manufactured sand is replaced by extra fine sand,the chloride diffusion coefficient is 3.6×10^(-12)m^(2)/s,which can still meet the design requirements.With the increase of sand ratio,the chloride diffusion coefficient decreases first and then increases.The water-binder ratio is controlled in the range of 0.36~0.38,and the chloride diffusion coefficient is less than 3.5×10^(-12)m^(2)/s.The hydration of slag component improves the pore structure of concrete,and forms more AFm and C-S-H,which improves the chloride binding capacity.The chloride diffusion coefficient of concrete with slag cement is 40%lower than that of OPC.