轴压与硫酸盐实时耦合作用下混凝土耐久性试验研究

Experimental Study of the Durability of Concrete Under Coupling Effect of Axial Compression and Sulfate Attack

通过测量混凝土的饱和面干吸水率和相对动弹性模量,研究了混凝土在轴压荷载与硫酸盐侵蚀耦合作用下耐久性能的时变规律,采用扫描电镜和X射线衍射仪研究非界面过渡区微观结构劣化规律.轴压应力比包括0、15%、30%和45%,硫酸钠溶液浓度包括0、5%和10%.试验结果表明:在45%应力比作用下,荷载对混凝土相对动弹性模量的劣化有显著促进作用,饱和面干吸水率随侵蚀龄期的增加呈逐渐增加规律.在30%及以下应力比作用下,混凝土的饱和面干吸水率随侵蚀龄期的增加呈先降低后增大的规律,且10%的硫酸钠溶液中的饱和面干吸水率后期增加较快;荷载对5%硫酸钠溶液中混凝土相对动弹性模量的劣化有抑制作用,30%应力比作用下的最明显.混凝土在轴压荷载与硫酸钠溶液侵蚀耦合作用下,随侵蚀龄期的增加,在45%应力比作用下,非界面过渡区微观结构呈逐渐劣化的规律;在30%及以下应力比作用下,非界面过渡区微观结构呈两阶段演化规律,在早期侵蚀阶段,钙矾石、石膏等侵蚀产物对微观结构有逐渐填充密实作用,后期钙矾石、石膏等的膨胀应力作用使微观结构产生微裂缝而逐渐劣化.

The time-dependent law of concrete durability under the coupling effects of axial compression load and sulfate attack was investigated by measuring the water absorption of the dry saturation surface and relative dynamic elastic modulus.Microstructure deterioration at non interfacial transition zone was studied by means of Scanning electron microscopy(SEM)and Xray diffraction(XRD).The effects of various stress ratio(0,15,30 and 45%)and different sulfate solution concentration(0,5 and 10%)were considered in this paper.The investigation showed that,the coupling effect of the stress ratio of 45%with sulfate attack has significantly accelerated the damage deterioration of the relative dynamic elastic modulus of concrete,and the water absorption of the dry saturation surface rate increased significantly.The axial load with stress ration of 30%or less coupled with 5%concentration of sodium sulfate solution attack has inhibitory effect on the degradation of the relative dynamic elastic modulus,and the inhibitory effect of stress ratio of 30%is more significant.Compared with 5%concentration of sodium sulfate solution,10%concentration of sodium sulfate solution has a significant acceleration effect on the deterioration of concrete.Under the real-time coupling action of axial compression load and sodium sulfate corrosion,with the increase of corrosion time,the erosion products such as ettringite and gypsum have gradually filling effect on microstructure at the early period,and later the expansion effect of the ettringite and gypsum will induce micro cracks and cause gradually deterioration in concrete.