Experimental Study On Dynamic Mechanical Properties Of Axially Carbonated Mortar Under Impact

Mortar and concrete are one of the most widely used materials in engineering construction.However,due to the existence of CO2 in the atmosphere,buildings will be continuously invaded by CO2 and carbonized.The generated carbides will change the mechanical parameters of materials,which will have a great impact on the structural performance and internal microstructure.At present,the research on carbonated mortar and concrete mainly focuses on the changes of microstructure and static mechanical properties,but rarely involves the dynamic mechanical properties of carbonated mortar and concrete.Buildings and structures are often subjected to dynamic load in the process of long-term use.Therefore,it is necessary to study the dynamic mechanical properties of carbonated mortar for buildings that need long-term use.In this paper,the axial carbonation tests of standard mortar specimens at different ages were carried out.The longitudinal wave velocity of specimens at different carbonation ages was measured by non-metallic ultrasonic detector.At the same time,the carbonation enhancement factor η was introduced to reflect the carbonation depth of the specimens.The impact dynamics of axially carbonated mortar under different carbonation ages was carried out by using a 50 mm diameter split Hopkinson pressure bar test device Compression test was carried out to study ’the dynamic mechanical properties,energy dissipation law,fracture morphology and fractal dimension of mortar after axial carbonization,which provided experimental basis for engineering construction and use.The main research contents and conclusions are as follows:Firstly,the mortar specimens were carbonized at different ages,and the density of mortar increased with the increase of carbonation age.With the increase of carbonization age,the carbonization enhancement factor η also increases,and the longitudinal wave velocity of the specimen increases as a whole,and the carbonization depth increases.There is a good correlation between the two.Secondly,using split Hopkinson pressure bar test system,the impact compression tests of carbonated specimens with different carbonation ages were carried out under five air pressures of 0.25MPa,0.35Mpa,0.45MPa,0.55mpa and 0.65Mpa.The results show that with the increase of impact pressure,the peak stress and peak strain of mortar also increase,showing a good linear correlation;with the increase of carbonation age,the same impact occurs Under the impact pressure,the peak stress of the specimen increases,the overall strength of the specimen increases,and the number of fragments and damage degree gradually decrease.Thirdly,the energy dissipation and fractal dimension of mortar specimens under different impact pressures are analyzed.The results show that:under normal conditions,with the increase of loading rate,all kinds of energy are increasing,and the reflection energy,absorption energy and specific energy absorption value have a good positive linear correlation with the incident energy;with the increase of carbonation age,the specific energy absorption value of mortar specimens shows an overall increasing trend,Under the same impact pressure,with the increase of carbonation age,the fracture degree of specimens decreases and the fractal dimension decreases.Figure:[46]Table:[9]Reference:[65]...