The Effect Of Mechanical Properties Of Rcc With Initial Pores

As a heterogeneous composite material widely used in infrastructure engineering construction,RCC inevitably has a certain degree of initial damage inside the structure,it mainly manifests in the form of pores,microcracks and bubbles.In order to reasonably explain the influence of internal structural characteristics of RCC on its mechanical properties,researchers have shifted their focus from the macro to the meso and micro levels,and the pore structure is regarded as an important part of concrete.In addition,the complex structure inside the RCC material also has an impact on the acoustic emission characteristics.In order to judge some physical states of RCC structure by analyzing the acoustic emission signal,it is necessary to understand the characteristics of concrete acoustic emission signals in different situations.In this paper,the effect of pore increment on the strength and its size effect of C20 RCC is studied systematically through tests.Based on the acoustic emission technique,a preliminary study was conducted on the acoustic emission characteristics of RCC materials.The main research contents and conclusions are as follows:(1)Strength tests were carried out on the C20 RCC standard specimens with four different pore contents.Based on the test results,the effect of pore increment on the strength of RCC was quantitatively analyzed,and the changing formula of compressive strength and splitting strength with porosity were fitted.The results show that when the pore content is low,there is a good exponential relationship between the strength of RCC and porosity.(2)Strength tests were carried out on C20 RCC specimens with different sizes and different pore contents.The influence of pore content on the strength size effect of RCC was discussed.The specimen sizes were 100mm×100mm×100mm,150mm×150mm×150mm and 200mm×200mm×200mm respectively.The research shows that there is a certain relationship between the strength size effect of RCC and the pore content.With the increase of porosity,the strength size effect of RCC becomes more obvious.(3)During the loading process of the RCC mechanical test,the acoustic emission characteristics of RCC under different stress conditions and the influence of self-structural factors on its acoustic emission characteristics and sound velocity were studied based on acoustic emission technology.The research shows that:1)The sound velocity of RCC is related to the density of the structure,with the decrease of the curing age or the increase of the pore content,the density of the RCC gradually decreases,the sound velocity gradually decreases;2)An increase in porosity or a reduction in specimen size will lead to an increase in the number of RCC acoustic emission hits at low stress levels,and an increased probability of acoustic emission events;3)The curing age and specimen size have significant influence on the activity of RCC acoustic emission signals,the smaller the curing age and the specimen size,the higher the activity of the RCC acoustic emission.