Experimental Study On Macro-Meso Compressive Property Of Concrete Exposed To Simulated Acid Rain Environment

Pollution of acid rain has attacked the attention of environmentalists worldwide. Large amounts of acid medium exist in acid rain environment,which have severe corrosion effects on the material of both concrete and reinforcing steel.It has been reported that many concrete structures servicing in the acid rain environment have been damaged severely long before their servicing lives.It is well known that mechanical property of concrete is the foundation for the analysis of load carrying capacity of the concrete structure.Therefore,it is crucial to discover the mechanical damage rule of concrete corroded by acid rain environment,and the research will have both theoretical and practical value.Funded by the National Science Foundation of China(Grant No.50708010), compressive property of concrete corroded by acid rain was studied based on both macro- and meso- scale.325 prism specimens(150×150×300mm) and some cubic specimens(100×100×100mm) were prepared to perform the test on the elastic modulus and compressive strength of concrete under different corrosion states.Considering the characteristic of acid rain in China,Sulfate and nitric acid solutions are mixed to simulate acid rain environments with 3 pH levels(pH 3.5,pH 2.5 and pH 1.5) respectively.Compressive properties of concrete were studied based on both macro- and meso-scale.Main contents of the paper are outlined as follows:Firstly,after being exposed to the simulated acid rain solutions for different periods, compressive test were executed on the concrete specimens under different corrosion states.Compressive properties of the corroded specimens(i.e.corrosion depth,mass loss,axial compressive strength,elastic modulus,etc.) are achieved.Comparing with the compressive property of non-corroded concrete specimens,effects of the acidity of acid rain on the performance of corroded concrete are discussed in detail.3 damage indices(relative mass variation ratio k_mc,relative strength variation ratio k_cc,and relative elastic modulus variation ratio k_Ec) were compared and discussed.It is shown that the k_cc is more suitable for the damage description of corrosion state of the concrete corroded by acid rain.On the other hand,ultrasonic nondestructive test were performed to measure the corrosion depth of the corroded concrete specimens.It is shown that the ultrasonic nondestructive method will provide an efficient way to measure the corrosion depth of concrete under acid environment.Based on the test results,a bilinear model which has a good correlation with the test results was put forward to evaluate the corrosion depth of concrete under different acid solutions.Then,meso- structures of concrete specimen before and after being corroded by the simulated acid rain were studied by means of computed tomography(CT) technology.Corrosion effects of acid rain on the meso-structure of the concrete specimen were discussed in detail.According to the CT original data,mesostructure of the concrete specimen were reconstructed,which found a basis for the numerical simulation of corrosion process of concrete specimen exposed to corrosion environment. Compression test was performed as well,and the compressive properties are achieved. The results will build a foundation for the macro-mechanical property evaluation of concrete based on meso scale.