低品质再生粗骨料混凝土抗溶蚀性能研究

Study on corrosion resistance of low quality recycled coarse aggregate concrete

为进一步探讨低品质再生粗骨料混凝土在水利工程结构领域的应用可行性,本试验主要从抗溶蚀耐久性出发,以天然粗骨料混凝土作为对照组,采用0.5 mol/L硝酸加速溶蚀试验,分别从宏观浸出行为指标以及微观结构损伤(SEM)两大方面揭示低品质再生粗骨料混凝土抗溶蚀性能经时劣化规律和损伤机理。结果表明,低品质再生粗骨料混凝土的力学性能劣于天然粗骨料混凝土,但28 d抗压强度可达到C30目标强度值;在硝酸加速溶蚀作用下,低品质再生粗骨料混凝土表现出比天然粗骨料混凝土更强的抗溶蚀耐久性,其抗压强度损失率、质量损失率、饱和面干吸水率均随溶蚀时间的增加而逐渐增大,初期劣化速率较快,45 d逐渐趋于平缓;由溶蚀深度与溶蚀时间的拟合关系得出,低品质再生粗骨料混凝土在自然软水环境下可使用至少50年,表明低品质再生粗骨料用于制备水利工程结构混凝土是可行的。

In order to further explore the application feasibility of low-quality recycled coarse aggregate concrete in the field of water conservancy engineering structure,this test mainly starts from the corrosion resistance durability,and takes the natural coarse aggregate concrete as the control.The accelerated dissolution test was carried out with 0.5 mol/L nitric acid to reveal the degradation law and damage mechanism of corrosion resistance of low-quality recycled coarse aggregate concrete from two aspects of macro leaching behavior index and microstructure damage(SEM).The results show that the mechanical properties of low quality recycled coarse aggregate concrete are inferior to that of natural coarse aggregate concrete,but the 28 d compressive strength can reach the C30 target strength value.The low-quality recycled coarse aggregate concrete shows good corrosion resistance than that of natural coarse aggregate concrete in the process of nitric acid accelerated dissolution.The compressive strength loss rate,mass loss rate,the water absorption of the dry saturation surface increase with the increase of dissolution time,and the degradation rate is fast at the initial stage,and gradually tends to be flat after 45 days.According to the fitting relationship between dissolution depth and dissolution time,low-quality recycled coarse aggregate concrete can be used in natural soft water environment for at least 50 years,which indicates that the low-quality recycled coarse aggregate is feasible for the preparation of hydraulic engineering structural concrete.