Study On The Experiments Of Micro And Dynamic Properties Of Concrete Under The Seawater Erosion

Concrete is one of the most major engineering material in marine construction, researcheson the micro and macro properties have important practical significance. In this paper,researches on the mechanical properties of concrete material under seawater attack were mainlydivided into two parts.One part is to take the SEM tests and XRD semi-quantitative analysis of cement stone aftersulfate or sulfate-chloride double factors attack. In this paper, two kinds of attack solution areconsidered. One kind is a single sulfate solution with concentration of respectively0%,3%,4%,5%and6%. Another kind is three types of sulfate-chloride double factors solution. The firsttype is the mixed solution with sulfate ion of3%and chloride ion of the same concentration.The second type is the mixed solution with sulfate ion of3%and chloride ion of3timesconcentration. The third type is the mixed solution with sulfate ion of5%and chloride ion of thesame concentration. At the same time, we manufacture three types of cement mortar sampleswith the water-cement ratio of0.45,0.55and0.65. After immerged in the attack solution fordifferent time, micro researches are carried out by using SEM and XRD methods. SEM is usedto investigate the attack products qualitatively and XRD is used to semi-quantitatively analyzethe percents of the attack product. The content of attack products in the samples whichrespectively were immersed in the sulfate solution or sulfate-chloride mixed solution werecompared to understand the attack mechanism under different attack factors.Another part is to analyze dynamic properties of concrete material under sulfate attack byadvanced Hopkinson pressure bar test and ultrasonic test. Three types of cement mortar sampleswith the water-cement ratio of0.45,0.55and0.65respectively were immerged in the differentconcentration of attack solutions for different time. After that, ultrasonic instrument wasemployed to obtain the longitudinal acoustic wave velocity of corresponding sample, and thenthe dynamic elastic moduluscan be determined. In succession, by using advanced Hopkinsontechnique, the propagation of impact wave in the specimen was experimentally studied.Furthermore, the one-dimensional stress-strain relationis also obtained by Lagrange methodbased on the path-line called “1sV+n”. By comparing the results obtained by ultrasonictechnique and those obtained by advanced Hopkinson technique, we found that the evolution trend of dynamic modulus of cement mortar under attack of sulfate is almost the same but theturning point from raising up to attenuation is different. The experimental results may providereference for concrete material will be better applied to practical projects under marineenvironment.Finally, the main conclusions are shown and some suggestions are presented for futureresearch as well.