风积沙混凝土盐冻多尺度劣化机制

Multi-scale degradation mechanism of aeolian sand concrete under salt-frost condition

研究风积沙混凝土盐冻劣化规律,揭示劣化机制对其推广应用有重要指导意义。基于室内快速冻融试验及力学特性试验研究了风积沙混凝土盐冻劣化规律,结合SEM、NMR、XRD等表征技术及损伤力学理论从多尺度揭示了盐冻劣化机制。结果表明:风积沙影响混凝土的抗冻性,100%掺量风积沙混凝土强度低,但抗冻性最好。混凝土质量损失率及抗压强度损失率均随盐冻循环次数的增加而增大,相对动弹性模量随盐冻循环次数的增大而减小。风积沙混凝土的盐冻损伤是一个物理-化学过程,界面过渡区(ITZ)骨-浆剥离及附近砂浆基质开裂是导致其宏观物理、力学性能退化的主要原因。风积沙可以改变混凝土内部的孔隙结构及水分传输路径,进而影响孔隙饱和度及混凝土的抗盐冻性能。

It is of great guiding significance to study the salt-frost degradation and reveal the degradation mechanism of aeolian sand concrete for its popularization and application.The salt-frost degradation rule of aeolian sand concrete was studied based on the fast indoor test and mechanical properties test,and its degradation mechanism was revealed from multi-scale combining with the SEM,XRD,NMR and damage mechanics theory.The results show that aeolian sand affects the frost resistance of concrete,and the optimal frost resistance is achieved with 100%aeolian sand replacement despite its low strength.The loss rates of mass and compressive strength increase with the increase number of salt-frost cycling,while the relative dynamic elastic modulus decreases with the increase number of salt-frost cycling.The salt-frost damage of aeolian sand concrete is dominated by physical-chemical effects,and the bone-slurry debonding in the interfacial transition zone(ITZ)and the cracking of the nearby mortar matrix are the main reasons for the degradation of its macroscopic physical and mechanical properties.Aeolian sand can change the pore structure of concrete and the moisture transmission path in it,thereby affects the pore saturation and the salt-frost resistance of concrete.