According to the damage mechanism of concrete material during the uniaxial compressive failure process,this paper further establishes the statistical damage constitutive model of concrete subjected to uniaxial compres...According to the damage mechanism of concrete material during the uniaxial compressive failure process,this paper further establishes the statistical damage constitutive model of concrete subjected to uniaxial compressive stress based on the statistical damage model under uniaxial tension. The damage evolution law in the direction subjected to pressure is confirmed by the tensile damage evolution process of lateral deformation due to the Poisson effect,and then the compressive stress-strain relationship is defined. The peak nominal stress state and the critical state occurring in the macro longitudinal distributed splitting cracks are distinguished. The whole loading process can be divided into the even damage phase and the local breakage phase. The concrete specimen is divided into the failure process zone and the resting unloading zone. The size effects during the local breakage phase under the uniaxial monotonic compressive process and the hysteretic phenomenon under the cyclic compressive loading process are analyzed. Finally,the comparison between theoretical results and experimental results preliminarily verifies the rationality and feasibility of understanding the failure mechanism of concrete through the statistical damage constitutional law.展开更多
To investigate the static compressive properties and mechanical damage evolution of rubber cement-based materials(RCBMs) with dry-and wet-curing conditions, uniaxial compression and cyclic loading-unloading tests were...To investigate the static compressive properties and mechanical damage evolution of rubber cement-based materials(RCBMs) with dry-and wet-curing conditions, uniaxial compression and cyclic loading-unloading tests were carried out on rubber cement mortar(RCM). The mechanical properties of the uniaxial compression specimens cured at 95%(wet-curing) and 50%(dry-curing) relative humidities and cyclic loading-unloading specimens cured at wet-curing were analyzed. Under uniaxial compression, the peak stress loss ratio is higher for dry-curing than for wet-curing. The peak strain decreases with the increase of rubber content, and the peak strain increases with the decrease of curing humidity. Under cyclic loading-unloading, the variation trends of residual strain differences of the normal cement mortar and RCM at each cyclic level with the number of cycles are basically the same, but the failure modes are different. The analysis of the internal mesostructure by a scanning electron microscope(SEM) shows that initial damage is further enhanced by reducing curing humidity and adding rubber aggregate. The damage constitutive model based on strain equivalence principle and statistical theories was used to describe the uniaxial compression characteristics of RCM, and the law of mechanical damage evolution was predicted.展开更多
The microscopic morphology and pore structure characteristics of concrete with composite admixtures(fly ash and mineral powder) after chlorine salt erosion were analyzed via scanning electron microscopy(SEM) and mercu...The microscopic morphology and pore structure characteristics of concrete with composite admixtures(fly ash and mineral powder) after chlorine salt erosion were analyzed via scanning electron microscopy(SEM) and mercury injection porosimetry(MIP), providing the basis for the design and maintenance of concrete shafts in coal mines. The above-mentioned characteristics were compared with the macroscopic characteristic of concrete fractures under uniaxial compression. The results show that the macroscopic fracture characteristics of concrete under uniaxial compression change from longitudinal split fracture and oblique section shear fracture to conjugate cant fracture, and the degree of breakage increases.Interface cracks, cement paste cracks, spherical surface cracks, and aggregate cracks appear in concrete under uniaxial compression. In the early stages of corrosion, the original cracks which are obvious are repaired. When the corrosion becomes more serious, cement paste cracks appear, and the number of harmful holes increases while the number of harmless holes decreases. This study also reveals the relationship between the macroscopic properties and microscopic structure of concrete under chloride salt erosion. Finally, the paper preliminarily discussed the relationship between the macroscopic properties and mesoscopic characteristics of concrete under chlorine salt erosion.展开更多
基金Sponsored by the Program for New Century Excellent Talents in University (NCET-05-0413)the National Natural Science Foundation of China(Grant No.90510018 and 50679006)the China Postdoctoral Science Foundation(Grant No.20090461166)
文摘According to the damage mechanism of concrete material during the uniaxial compressive failure process,this paper further establishes the statistical damage constitutive model of concrete subjected to uniaxial compressive stress based on the statistical damage model under uniaxial tension. The damage evolution law in the direction subjected to pressure is confirmed by the tensile damage evolution process of lateral deformation due to the Poisson effect,and then the compressive stress-strain relationship is defined. The peak nominal stress state and the critical state occurring in the macro longitudinal distributed splitting cracks are distinguished. The whole loading process can be divided into the even damage phase and the local breakage phase. The concrete specimen is divided into the failure process zone and the resting unloading zone. The size effects during the local breakage phase under the uniaxial monotonic compressive process and the hysteretic phenomenon under the cyclic compressive loading process are analyzed. Finally,the comparison between theoretical results and experimental results preliminarily verifies the rationality and feasibility of understanding the failure mechanism of concrete through the statistical damage constitutional law.
基金Projects(52008003,52074009)supported by the National Natural Science Foundation of ChinaProject(201904a07020081)supported by the Key Research and Development Program Project of Anhui Province,ChinaProject(1908085QE213)supported by the Nature Science Foundation of Anhui Province,China。
文摘To investigate the static compressive properties and mechanical damage evolution of rubber cement-based materials(RCBMs) with dry-and wet-curing conditions, uniaxial compression and cyclic loading-unloading tests were carried out on rubber cement mortar(RCM). The mechanical properties of the uniaxial compression specimens cured at 95%(wet-curing) and 50%(dry-curing) relative humidities and cyclic loading-unloading specimens cured at wet-curing were analyzed. Under uniaxial compression, the peak stress loss ratio is higher for dry-curing than for wet-curing. The peak strain decreases with the increase of rubber content, and the peak strain increases with the decrease of curing humidity. Under cyclic loading-unloading, the variation trends of residual strain differences of the normal cement mortar and RCM at each cyclic level with the number of cycles are basically the same, but the failure modes are different. The analysis of the internal mesostructure by a scanning electron microscope(SEM) shows that initial damage is further enhanced by reducing curing humidity and adding rubber aggregate. The damage constitutive model based on strain equivalence principle and statistical theories was used to describe the uniaxial compression characteristics of RCM, and the law of mechanical damage evolution was predicted.
基金The authors gratefully acknowledge the financial support for this work,provided by the Outstanding Youth Science Foundation of China(No.51322401)the Key Project of Chinese National Programs for Fundamental Research and Development of China(No.2015CB251601)+1 种基金the Science and Technology Project of the Chinese Ministry of Housing and Urban-Rural Construction of China(Nos.2013-K4-22 and 2014-K4-042)the General Program of Chinese National Building Materials Industry Technology Innovation Program of China(Nos.2014-M5-1 and 2014-M5-2)
文摘The microscopic morphology and pore structure characteristics of concrete with composite admixtures(fly ash and mineral powder) after chlorine salt erosion were analyzed via scanning electron microscopy(SEM) and mercury injection porosimetry(MIP), providing the basis for the design and maintenance of concrete shafts in coal mines. The above-mentioned characteristics were compared with the macroscopic characteristic of concrete fractures under uniaxial compression. The results show that the macroscopic fracture characteristics of concrete under uniaxial compression change from longitudinal split fracture and oblique section shear fracture to conjugate cant fracture, and the degree of breakage increases.Interface cracks, cement paste cracks, spherical surface cracks, and aggregate cracks appear in concrete under uniaxial compression. In the early stages of corrosion, the original cracks which are obvious are repaired. When the corrosion becomes more serious, cement paste cracks appear, and the number of harmful holes increases while the number of harmless holes decreases. This study also reveals the relationship between the macroscopic properties and microscopic structure of concrete under chloride salt erosion. Finally, the paper preliminarily discussed the relationship between the macroscopic properties and mesoscopic characteristics of concrete under chlorine salt erosion.