Experimental Study On Dynamic Mechanical Properties Of Roller Compacted Concrete Under Freeze-Thaw Cycle

RCC technology has been used in dam construction since the early 1970 s,and has been widely promoted due to its advantages such as simple temperature control measures,fast construction speed,low cement consumption and low investment cost.The service environment of RCC structures in northwest China and other cold regions is complex and the adverse environmental factors have adverse effects on the structure performance.Therefore,on the basis of considering the durability of RCC,the study of dynamic mechanical properties of RCC under freeze-thaw cycle has important application value for the construction and development of water conservancy projects in China.In this paper,the freeze-thaw cycle test,CT scan test and dynamic mechanical property test were combined,and the number of freeze-thaw cycles and loading rate were taken as reference factors to study the RCC before and after freeze-thaw damage and loading,so as to provide reference basis for RCC dam construction.The research conclusions are as follows:(1)The freeze-thaw cycle test was carried out for the RCC specimens.The damage degree of the specimens was determined by comparing the variation rules of the parameters of the RCC specimens under different freeze-thaw cycles.The results show that the damage degree of RCC specimens is more and more serious with the increase of freeze-thaw cycles.(2)Uniaxial dynamic compression tests were carried out on RCC specimens under different loading rates after freeze-thaw cycles.The results show that the compressive strength of RCC decreases with the increase of freeze-thaw cycles at the same loading rate.Under the same freeze-thaw cycles,the compressive strength of RCC increases with the increase of loading rate.(3)Four-point bending test was carried out for prism specimens.The bending strength,load-displacement curve and peak load of RCC under different freeze-thaw cycles and loading rates are summarized.The results show that the compressive strength of RCC is positively correlated with the loading rate under the same freeze-thaw cycles.Under the same loading rate,the bending strength of RCC is negatively correlated with the number of freeze-thaw cycles.(4)CT technology was used to scan RCC cube specimens after 0,25,50 and 75freeze-thaw cycles.It was found that the more the freeze-thaw cycles were,the more serious the surface loss was,and the more pores and microcracks were in the specimens.(5)under different loading rate for RCC CT scanning test specimens before and after loading,the Voxel Studio Recon and Avizo software to scan files get specimens under different loading rate further processing of three-dimensional image,through the specimen internal pore,the distribution features of the crack,from the mesoscopic level analysis ofroller compacted concrete specimen failure process.The results show that the damage degree of RCC specimens after loading is obviously more serious than that before loading.With the increase of the loading rate,the cracks of the loaded RCC specimens increased,and the cracks crossed and dispersed.